🕷️ Crawler Inspector

[](https://www.cyberciti.biz/faq/) [nixCraft](https://www.cyberciti.biz/) → [Howto](https://www.cyberciti.biz/faq/) → [BASH Shell](https://www.cyberciti.biz/faq/category/bash-shell/) → Bash for loop syntax and examples # [Bash For Loop Examples](https://www.cyberciti.biz/faq/bash-for-loop/) Author: Vivek Gite Last updated: January 31, 2025 [270 comments](https://www.cyberciti.biz/faq/bash-for-loop/#comments) [](https://www.cyberciti.biz/faq/category/bash-shell/ "See all Bash/Shell scripting related FAQ") How do I use bash for loop to repeat certain task under Linux / UNIX operating system? How can I set infinite loops using for statement? How do I use three-parameter bash for loop control expression? ## What is a Bash for loop? A bash for loop is a bash programming language statement which allows code to be repeatedly executed. A for loop is classified as an iteration statement i.e. it is the repetition of a process within a bash script. For example, you can run UNIX command or task 5 times or read and process list of files using a for loop. A for loop can be used at a shell prompt or within a shell script itself. | Tutorial requirements | | |---|---| | Requirements | Linux or Unix | | Root privileges | No | | Difficulty level | [Easy](https://www.cyberciti.biz/faq/tag/easy/ "See all Easy Linux / Unix System Administrator Tutorials") | | Category | [Linux shell scripting](https://bash.cyberciti.biz/guide/Main_Page "See Linux Bash Shell Scripting Tutorial") | | Prerequisites | Bash | | OS compatibility | BSD • [Linux](https://www.cyberciti.biz/faq/category/linux/ "See all Linux distributions tutorials") • [macOS](https://www.cyberciti.biz/faq/category/mac-os-x/ "See all macOS (OS X) tutorials") • [Unix](https://www.cyberciti.biz/faq/category/unix/ "See all Unix tutorials") | | Est. reading time | 10 minutes | | Table of contents ↓ [1 Syntax](https://www.cyberciti.biz/faq/bash-for-loop/#Syntax "Syntax") [2 Examples](https://www.cyberciti.biz/faq/bash-for-loop/#Examples "Examples") [3 seq command](https://www.cyberciti.biz/faq/bash-for-loop/#seq_command "seq command") [4 C style for loop](https://www.cyberciti.biz/faq/bash-for-loop/#C_style_for_loop "C style for loop") [5 Infinite loops](https://www.cyberciti.biz/faq/bash-for-loop/#Infinite_loops "Infinite loops") [6 Conditional exit with break](https://www.cyberciti.biz/faq/bash-for-loop/#Conditional_exit_with_break "Conditional exit with break") [7 continue statement](https://www.cyberciti.biz/faq/bash-for-loop/#continue_statement "continue statement") [8 For loop with array elements](https://www.cyberciti.biz/faq/bash-for-loop/#For_loop_with_array_elements "For loop with array elements") [9 Shell variable loop](https://www.cyberciti.biz/faq/bash-for-loop/#Shell_variable_loop "Shell variable loop") [10 Loop with a number](https://www.cyberciti.biz/faq/bash-for-loop/#Loop_with_a_number "Loop with a number") [11 Loop with strings](https://www.cyberciti.biz/faq/bash-for-loop/#Loop_with_strings "Loop with strings") [12 Command substitution](https://www.cyberciti.biz/faq/bash-for-loop/#Command_substitution "Command substitution") [13 Command-line arguments](https://www.cyberciti.biz/faq/bash-for-loop/#Command-line_arguments "Command-line arguments") [14 Putting all together](https://www.cyberciti.biz/faq/bash-for-loop/#Putting_all_together "Putting all together") [15 Related media](https://www.cyberciti.biz/faq/bash-for-loop/#Related_media "Related media") [16 Conclusion](https://www.cyberciti.biz/faq/bash-for-loop/#Conclusion "Conclusion") | | ## for loop syntax Numeric ranges for syntax is as follows: ``` for VARIABLE in 1 2 3 4 5 .. N do command1 command2 commandN done ``` OR ``` for VARIABLE in file1 file2 file3 do command1 on $VARIABLE command2 commandN done ``` OR ``` for OUTPUT in $(Linux-Or-Unix-Command-Here) do command1 on $OUTPUT command2 on $OUTPUT commandN done ``` ## Examples  This type of for loop is characterized by counting. The range is specified by a beginning (\#1) and ending number (\#5). The for loop executes a sequence of commands for each member in a list of items. A representative example in BASH is as follows to display welcome message 5 times with for loop: ``` #!/bin/bash for i in 1 2 3 4 5 do echo "Welcome $i times" done ``` Sometimes you may need to set a step value (allowing one to count by two’s or to count backwards for instance). Latest **bash version 3.0+** has inbuilt support for setting up ranges: ``` #!/bin/bash for i in {1..5} do echo "Welcome $i times" done ``` [Bash version 4.0+](https://www.cyberciti.biz/faq/how-do-i-check-my-bash-version/ "How do I check my bash version?") has inbuilt support for setting up a step value using {START**..**END**..**INCREMENT} syntax: ``` #!/bin/bash echo "Bash version ${BASH_VERSION}..." for i in {0..10..2} do echo "Welcome $i times" done ``` Sample outputs: ``` Bash version 4.0.33(0)-release... Welcome 0 times Welcome 2 times Welcome 4 times Welcome 6 times Welcome 8 times Welcome 10 times ``` ### The seq command to create standard bash for Loop (outdated method) **WARNING\!** The seq command print a sequence of numbers and it is here due to historical reasons. The following examples is only recommend for older bash version. All users (bash v3.x+) are recommended to use the above syntax. The [seq command](https://www.cyberciti.biz/tips/how-to-generating-print-range-sequence-of-numbers.html) can be used as follows. A representative example in seq is as follows: ``` #!/bin/bash for i in $(seq 1 2 20) do echo "Welcome $i times" done ``` There is no good reason to use an external command such as seq to count and increment numbers in the for loop, hence it is recommend that you avoid using seq. The builtin command are fast. ## Three-expression bash for loops syntax This type of for loop share a common heritage with the C programming language. It is characterized by a three-parameter loop control expression; consisting of an initializer (EXP1), a loop-test or condition (EXP2), and a counting expression/step (EXP3). ``` for (( EXP1; EXP2; EXP3 )) do command1 command2 command3 done ## The C-style Bash for loop ## for (( initializer; condition; step )) do shell_COMMANDS done ``` A representative three-expression example in bash as follows: ``` #!/bin/bash # set counter 'c' to 1 and condition # c is less than or equal to 5 for (( c=1; c<=5; c++ )) do echo "Welcome $c times" done ``` Sample output: ``` Welcome 1 times Welcome 2 times Welcome 3 times Welcome 4 times Welcome 5 times ``` ## How do I use for as infinite loops? Infinite for loop can be created with empty expressions, such as: ``` #!/bin/bash for (( ; ; )) do echo "infinite loops [ hit CTRL+C to stop]" done ``` ## Conditional exit with break You can do early exit with break statement inside the for loop. You can exit from within a FOR, WHILE or UNTIL loop using break. General break statement inside the for loop: ``` for I in 1 2 3 4 5 do statements1 #Executed for all values of ''I'', up to a disaster-condition if any. statements2 if (disaster-condition) then break #Abandon the loop. fi statements3 #While good and, no disaster-condition. done ``` Following shell script will go though all files stored in /etc directory. The for loop will be abandon when [/etc/resolv.conf](https://bash.cyberciti.biz/guide//etc/resolv.conf "/etc/resolv.conf - Linux Bash Shell Scripting Tutorial Wiki") file found: ``` #!/bin/bash # Count dns name server in the /etc/resolv.conf if found for file in /etc/* do # check if file exists in bash using the if # if [ "${file}" == "/etc/resolv.conf" ] then countNameservers=$(grep -c nameserver /etc/resolv.conf) echo "Total dns ${countNameservers} nameservers defined in ${file}" break fi done ``` Outputs: ``` Total dns 2 nameservers defined in /etc/resolv.conf ``` ### Early continuation with continue statement To resume the next iteration of the enclosing FOR, WHILE or UNTIL loop use continue statement. ``` for I in 1 2 3 4 5 do statements1 #Executed for all values of ''I'', up to a disaster-condition if any. statements2 if (condition) then continue #Go to next iteration of I in the loop and skip statements3 fi statements3 done ``` This script make backup of all file names specified on command line. If .bak file exists, it will skip the cp command. ``` #!/bin/bash FILES="$@" for f in $FILES do # if .bak backup file exists, read next file if [ -f ${f}.bak ] then echo "Skiping $f file..." continue # read next file and skip the cp command fi # we are here means no backup file exists, just use cp command to copy file /bin/cp $f $f.bak done ``` ## For loop with array elements In this example, we use the for loop to iterate over an array of elements defined as follows: ``` # Set three aws zones to create RDS instances DB_AWS_ZONE=('us-east-2a' 'us-west-1a' 'eu-central-1a') for zone in "${DB_AWS_ZONE[@]}" do echo "Creating rds (DB) server in $zone, please wait ..." aws rds create-db-instance \ --availability-zone "$zone" \ --allocated-storage 20 --db-instance-class db.m1.small \ --db-instance-identifier test-instance \ --engine mariadb \ --master-username my_user_name \ --master-user-password my_password_here done ``` ## Loop with a shell variable Sometimes we store important data in the shell variable, and we can use for a loop as follows to read the data to [open ssh TCP port 22 using the ufw](https://www.cyberciti.biz/faq/ufw-allow-incoming-ssh-connections-from-a-specific-ip-address-subnet-on-ubuntu-debian/ "How to open ssh 22/TCP port using ufw on Ubuntu/Debian Linux"): ``` # Defines a variable called _admin_ip that contains a list of IP addresses. # The IP addresses are separated by the pipe character (|). _admin_ip="202.54.1.33|MUM_VPN_GATEWAY 23.1.2.3|DEL_VPN_GATEWAY 13.1.2.3|SG_VPN_GATEWAY" for e in $_admin_ip do ufw allow from "${e%%|*}" to any port 22 proto tcp comment 'Open SSH port for ${e##*|}' done ``` - The for loop example allows Linux sysadmin to open SSH TCP port from the IP addresses in the \$\_admin\_ip variable. This is helpfor for allowing developers, users and administrators to connect to your server from remote locations with specific IP address defined in the list. - The for loop iterates over the IP addresses in the \_admin\_ip variable. - For each IP address, the [ufw command](https://www.cyberciti.biz/faq/how-to-set-up-ufw-firewall-on-ubuntu-24-04-lts-in-5-minutes/ "How to Set Up UFW Firewall on Ubuntu 24.04 LTS in 5 Minutes") command is used to allow SSH connections from that IP address stored in the `$e`. The \${e%%\|\*} bash expression extracts the part of the IP address before the pipe character using [parameter expansion modifiers](https://www.cyberciti.biz/tips/bash-shell-parameter-substitution-2.html "How To Use Bash Parameter Substitution Like A Pro"). - The [ufw command](https://www.cyberciti.biz/faq/how-to-set-up-ufw-firewall-on-ubuntu-24-04-lts-in-5-minutes/ "How to Set Up UFW Firewall on Ubuntu 24.04 LTS in 5 Minutes") allows ssh connections from the specified IP address to any port on the local Linux server. ## Loop with a number We can specify a range in loops as follows: ``` for i in {START..END} do commands done ## step value ## for i in {START..END..STEP} do commands done ## example: ping cbz01, cbz02, cbz03, and cbz04 using a loop ## for i in 0{1..4} do h="cbz${i}" ping -c 1 -q "$h" &>/dev/null if [ $? -eq 0 ] then echo "server $h alive" else echo "server $h dead or can not ping." fi done ``` ## Loop with strings Say we have a variable named PKGS, and we need to loop through a list of strings to install those packages: ``` # Install the PHP packages listed in the PKGS variable. PKGS="php7-openssl-7.3 php7-common-7.3 php7-fpm-7.3 php7-opcache-7.3 php7-7.3" for p in $PKGS do echo "Installing $p package" sudo apk add "$p" done ``` The for loop iterates over the PHP package names in the PKGS variable. For each PHP package name, the [echo command](https://bash.cyberciti.biz/guide/Echo_Command "Echo Command - Linux Bash Shell Scripting Tutorial Wiki") shows a message stating that the package is being installed on your Alpine Linux machine. The sudo command is used to run the [apk command](https://www.cyberciti.biz/faq/10-alpine-linux-apk-command-examples/ "10 Alpine Linux apk Command Examples") to add installs the specified package stored the \$p variable. ## Command substitution [Command substitution](https://bash.cyberciti.biz/guide/Command_substitution) means run a shell command and store its output to a variable. For example: ``` up=$(uptime) echo "Server uptime is $up" ``` The for Loop argument list also workes command substitution as follows: ``` for var in $(command) do print "$var" done ## example ## ## Show the name of every PDF file in the /nas directory: for f in $(ls /nas/*.pdf) do printf "File is %s\n" "$f" done ``` The bash for loop iterates over the output of the ls command. The `ls` shows and list the contents of the /nas directory on your Linux or Unix machine. The `*.pdf` pattern matches all files with the .pdf extension. The `$(ls /nas/*.pdf)` command expands to a list of all PDF files in the /nas directory. The [printf command](https://bash.cyberciti.biz/guide/Printf_command "Printf command - Linux Bash Shell Scripting Tutorial Wiki") prints each file name to the [standard output](https://bash.cyberciti.biz/guide/Standard_output)/screen. ## Command-line arguments A [command line argument](https://bash.cyberciti.biz/guide/Shell_command_line_parameters) is nothing but an argument sent to a program being called. A program can take any number of command line arguments. For example, we are going to use the [grep command](https://www.cyberciti.biz/faq/howto-use-grep-command-in-linux-unix/ "How to use grep command In Linux / UNIX with examples") to search for user names in the [/etc/passwd](https://www.cyberciti.biz/faq/understanding-etcpasswd-file-format/ "Understanding /etc/passwd File Format") file: `$ grep 'vivek' /etc/passwd` grep is the name of an actual command and shell executed this command when you type command at shell prompt. The first word on the command line is: - grep – name of the command to be executed. - Everything else on command line is taken as arguments to this command. The for Loop argument list also accepts [Command-line arguments/parameters](https://bash.cyberciti.biz/guide/Shell_command_line_parameters) as follows: ``` ## $@ expands to the positional parameters, starting from one. ## for i in $@ do echo "Script arg is $i" done ``` You run it as follows: `$ ./script one foo bar` ## Putting all together Bash for loop is useful for automating repetitive tasks in IT. Let us see how to run a simple command (such as uptime) on multiple Linux or Unix servers: ``` for s in server1 server2 server3 do ssh vivek@${s} "uptime" done ``` OR combine the [echo command](https://bash.cyberciti.biz/guide/Echo_Command "Echo Command - Linux Bash Shell Scripting Tutorial Wiki") along with [command substitution](https://bash.cyberciti.biz/guide/Command_substitution) as follows: ``` for s in server1 server2 server3 do echo "Server ${s}: $(ssh vivek@${s} uptime)" done ``` Sample outputs: ``` Server server1: 09:34:46 up 12 days, 21:57, 0 users, load average: 0.08, 0.09, 0.09 Server server2: 09:34:50 up 17 days, 2:30, 0 users, load average: 0.03, 0.03, 0.00 Server server3: 09:34:53 up 17 days, 2:31, 0 users, load average: 0.04, 0.04, 0.00 ``` In this standard bash for loop example we are going to update all CentOS/RHEL based servers using the [yum command](https://www.cyberciti.biz/faq/rhel-centos-fedora-linux-yum-command-howto/ "How to use the yum command on Linux (CentOS/RHEL)") or [apt command](https://www.cyberciti.biz/faq/ubuntu-lts-debian-linux-apt-command-examples/ "apt Command Examples for Ubuntu/Debian Linux")/[apt-get command](https://www.cyberciti.biz/tips/linux-debian-package-management-cheat-sheet.html "Ubuntu/Debian Linux apt-get package management cheat sheet") in case we have a Debian/Ubuntu based servers: ``` ## CENTOS/RHEL example (for fedora replace yum with dnf) ## for s in server0{1..8} do echo "*** Patching and updating ${s} ***" ssh root@${s} -- "yum -y update" done ``` Here is simple but useful shell script example named patch-debian-vm.sh: ``` #!/usr/bin/env bash # Purpose: Update all my Linode servers powered by Debian/Ubuntu Linux # Name: patch-debian-vm.sh # Author: Vivek Gite under GPL v2.x+ # ---------------------------------------- log="/tmp/apt-get.log" >"${log}" for s in ln.cbz0{1..5} do echo "Updating and patching $s, please wait..." | tee -a "${log}" ssh root@${s} -- apt-get -q -y update >/dev/null ssh root@${s} -- DEBIAN_FRONTEND=noninteractive apt-get -y -q upgrade >>"${log}" done echo "Check $log file for details." ``` See why we used [DEBIAN\_FRONTEND apt-get variable](https://www.cyberciti.biz/faq/explain-debian_frontend-apt-get-variable-for-ubuntu-debian/) to avoid any prompts during updates. It would be best if you [set up ssh keys](https://www.cyberciti.biz/faq/how-to-set-up-ssh-keys-on-linux-unix/) for automation purposes or running scripts from [Linux/Unix cron jobs](https://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/). ### Finding ping time for multiple IP addresses Here is my sample code for the file named find-ping-time.sh ``` #!/bin/bash # Purpose: Ping all of the IP addresses associated with my domain name www.cyberciti.biz # Name: find-ping-time.sh # Author: Vivek Gite under GPL v2.x+ # ----------------------------------- ips="$(host -t a www.cyberciti.biz | awk '{ print $4}')" for i in $ips; do ping -q -c 4 "$i"; done ``` This will produce average stats as follows, indicating that multiple load balancer ICMP ECHO\_REQUEST average time was 19-20 milliseconds ``` PING 104.22.10.214 (104.22.10.214) 56(84) bytes of data. --- 104.22.10.214 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3006ms rtt min/avg/max/mdev = 20.612/21.255/22.054/0.624 ms PING 172.67.7.239 (172.67.7.239) 56(84) bytes of data. --- 172.67.7.239 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3005ms rtt min/avg/max/mdev = 19.199/20.279/21.433/0.862 ms PING 104.22.11.214 (104.22.11.214) 56(84) bytes of data. --- 104.22.11.214 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3005ms rtt min/avg/max/mdev = 20.232/20.710/21.500/0.479 ms ``` The [host command](https://www.cyberciti.biz/faq/linux-unix-host-command-examples-usage-syntax/ "Linux and Unix host Command Examples") is used to resolve a domain name to its IP addresses and The awk command is used to extract the IP addresses from the output of the host command. Finally, the bash for loop iterates over the list of IP addresses. For each IP address, the [ping command](https://www.cyberciti.biz/faq/unix-ping-command-examples/ "UNIX and Linux ping Command Examples") to send 4 requests and print the stats on the screen. ## Check out related media This tutorial is also available in a quick video format. The video shows some additional and practical examples such as converting all flac music files to mp3 format, all avi files to mp4 video format, unzipping multiple zip files or tar balls, gathering uptime information from multiple Linux/Unix servers, detecting remote web-server using domain names and much more. [Video 01: 15 Bash For Loop Examples for Linux / Unix / OS X Shell Scripting](https://youtu.be/ocXb3qeg7Es) ## Conclusion You learned how to use the bash for loop with various example. For loops can save time and help you with automation for tiny tasks. However, for complicated IT automation tasks, you should use tools like [Ansible](https://www.cyberciti.biz/faq/tag/ansible/), Salt, Chef, [pssh](https://www.cyberciti.biz/cloud-computing/how-to-use-pssh-parallel-ssh-program-on-linux-unix/) and others. See the following resources for more info. - See all sample for loop shell [script in our](https://bash.cyberciti.biz/script/for-loop/) bash shell directory - Bash for loop [syntax and usage page](https://bash.cyberciti.biz/guide/For_loop) from the Linux shell scripting wiki - Also read the following manual pages using [man command](https://bash.cyberciti.biz/guide/Man_command "Man command - Linux Bash Shell Scripting Tutorial Wiki")/info command or [help command](https://bash.cyberciti.biz/guide/Help_command "help command - Linux Bash Shell Scripting Tutorial Wiki"): ``` $ man bash $ info bash $ help for $ help { $ help break $ help continue ``` 🥺 Was this helpful? Please add [a comment to show your appreciation or feedback](https://www.cyberciti.biz/faq/bash-for-loop/#respond "Please add your comment below ↓ to show your appreciation or feedback to the author"). [Vivek Gite](https://www.vivekgite.com/) is an expert IT Consultant with over 25 years of experience, specializing in Linux and open source solutions. He writes about Linux, macOS, Unix, IT, programming, infosec, and open source. Follow his work via [RSS feed](https://www.cyberciti.com/atom/atom.xml "Get nixCraft updates using RSS feed") or [email newsletter](https://newsletter.cyberciti.com/subscription?f=1ojtmiv8892KQzyMsTF4YPr1pPSAhX2rq7Qfe5DiHMgXwKo892di4MTWyOdd976343rcNR6LhdG1f7k9H8929kMNMdWu3g "Get nixCraft updates using Email"). Comments on this entry are closed. - Jadu Saikia Nov 2, 2008 @ 15:37 Nice one. All the examples are explained well, thanks Vivek. seq 1 2 20 output can also be produced using jot jot – 1 20 2 The infinite loops as everyone knows have the following alternatives. while(true) or while : //Jadu [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39102 "permalink to this comment") - Sean Nov 4, 2008 @ 2:20 The last example can also be produced without the ” in \$FILES”: \#!/bin/sh for f do \# For-Loop body done If the ” in …” is excluded, the loop will run as if “in \$@” was given. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39113 "permalink to this comment") - Milad Mar 5, 2021 @ 11:07 Interesting , very nice [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-933684 "permalink to this comment") - Andreas Nov 13, 2008 @ 4:53 Nice explanation tutorial. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39200 "permalink to this comment") - Manish Nov 25, 2008 @ 6:33 hey vivek i tried the following syntax for for loop suggested by u but both dint work… 1. \#!/bin/bash for (( c=1; c\<=5; c++ )) do echo “Welcome \$c times…” done 2\. \#!/bin/bash for i in {1..5} do echo “Welcome \$i times” done got error for both the syntax 1. unexpected ‘(‘ 2. it printed welcome {1..5} times instead repeating it… help..? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39302 "permalink to this comment") - balamurugan Aug 11, 2010 @ 5:24 hi manish your both coding are correct… before execute you must give the execution permission for that file… so you try following steps… 1.goto terminal 2. vim simple 3.then write the following code.. for (( c=1; c\<=5; c++ )) do echo “Welcome \$c times…” done 4\.then save and quit 5.chmod 744 simple 6. ./simple i hope surely it will help you… [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48722 "permalink to this comment") - Manish Kumar Mishra Feb 3, 2011 @ 5:16 It works properly just check it again.. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55315 "permalink to this comment") - Dr. Stefan Gruenwald Apr 1, 2011 @ 3:53 I can help you on 2. — You were not using the Bash 3.0 or higher. Upgrade your bash and it will work. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56881 "permalink to this comment") - Niranjan May 10, 2011 @ 1:35 Hi All, I have some ‘.gif’ and ‘.jpg’ files in a directory named Pictures in my home directory. I need to write bash script that would create 2 separate html files such as page1.html and page2.html one for gif files and the other for jpg files. And when i execute the script i need to have the html files in the Pictures directory and should have the contents as follows: filename.jpg filename.jpg filename.gif filename.gif Please help me out. Thanks in advance [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59334 "permalink to this comment") - krist0ph3r May 30, 2011 @ 14:37 your problem is very easy to solve using the examples on the page. in addition to the for loops, you will need to use the echo command, the redirection operator \>\> and a basic knowledge of html. your script should do: 1\. create a html file with the header, opening body tags etc. 2. have a loop for all jpg files 2.1 inside the loop, print one line with the html code for an image, using the image’s filename 3. close the loop, add closing html tags 4-6. same as 1-3, but for .gif instead of .jpg [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59705 "permalink to this comment") - lascost Dec 6, 2008 @ 18:15 i tried the last example but i seen dint work ``` #!/bin/bash set -x FILLES="$@" CP=$(which cp) for f in $FILES do if [ -f ${f}.bak ] then echo "skiping $f file" continue # read netxt file and skip cp command fi $CP $f $f.bak done ``` i would like know where is the error [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39378 "permalink to this comment") - Johnny Rosenberg Aug 6, 2015 @ 15:06 Maybe correcting your misspelled variable ”FILLES” would be a step forward? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-725347 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Dec 13, 2008 @ 16:56 Replace ``` FILLES="$@" ``` With ``` FILES="$@" ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-39453 "permalink to this comment") - lo2y Jan 28, 2009 @ 10:10 hi guys . can any one help me . i need a script to check the file /var/log/messages every 10 minutes .and if its has the following log : ext3\_orphan\_cleanup: deleting unreferenced to apply the following command sendsms to wut ever . thnx alot [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-40028 "permalink to this comment") - swatkat Feb 12, 2009 @ 14:06 i would like to breakk a csv file depending upon two criteria. 1\. SIngle file should not be more than 100 lines 2. The third column if has same value on the 100th line as that of the 101th line, the complete line should be included in the 2nd file. so., now, 1st file will have 99 lines and 2nd file will have 100 lines, ifthe above 2nd condition does not repeats., [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-40255 "permalink to this comment") - archana Mar 16, 2009 @ 23:53 for file in \$(ls 0902\*0010202.TLG); do day=\$(echo \$file \| cut -c 1-6) grep ^203 \$file \| cut -d, -f3 \| sort \| uniq -c \| while read line; do cnt=\$(echo \$line \| cut -d” ” -f1) acct=\$(echo \$line \| cut -d” ” -f2) echo “Date 20\${day} Account \${acct} had \${cnt} 203’s” \>\> Feb\_report.txt done done when i run it it gives me a syntax error ins@ARTMGA01\> ./arc.sh ./arc.sh: syntax error at line 4: \`\$’ unexpected could you help [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-40783 "permalink to this comment") - Navneet Apr 20, 2009 @ 10:57 Good examples!! easily understood [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-41264 "permalink to this comment") - firmit Jun 7, 2009 @ 17:06 Hi How do I read line by line in a file, and use these in a loop? I have a file I read in (cmd max\_cpu): firefox 15 conky 1 cmds=\$(cat file) But \$cmds now consist of n items, all being “equal” – it does not split on each line to a new array. I expected that by looping over \$cmds, I’d get a 2D array…. I did not. Otherwise, excellent tutorial\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-41954 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Jun 7, 2009 @ 17:56 Try: ``` FILE=/etc/passwd while read line do # store field 1 F1=$(echo $line|cut -d$FS -f1) # store field 2 F2=$(echo $line|cut -d$FS -f6) # store field F3=$(echo $line|cut -d$FS -f7) echo "User \"$F1\" home directory is $F2 and login shell is $F3" done < $FILE ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-41956 "permalink to this comment") - Andi Reinbrech Nov 18, 2010 @ 19:42 I know this is an ancient thread, but thought this trick might be helpful to someone: For the above example with all the cuts, simply do `` set `echo $line` `` This will split line into positional parameters and you can after the set simply say `F1=$1; F2=$2; F3=$3` I used this a lot many years ago on solaris with “set \`date\`”, it neatly splits the whole date string into variables and saves lots of messy cutting :-) … no, you can’t change the FS, if it’s not space, you can’t use this method [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-50959 "permalink to this comment") - Dana Good Feb 13, 2012 @ 3:05 This \*is\* helpful – good knowledge to have. I’ll go give it a try. Thanks\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-67942 "permalink to this comment") - Alvin Aug 17, 2010 @ 12:09 Hi Vivek, Please help I was trying to use your code in a script similar issue trying to use a csv file with three columns (loginname,surname,firname) as input for a file that will be executed fileA loginN,ssn,ffn ab1pp1,ab1,pp1 bb1oo1,bb1,oo1 cc1qq1,cc1,qq1 \#file to be changed cmdch.sh echo “your login name is \$loginn, your surname is \$ssn and your firname \$ffn” Program \#!/bin/bash LINNUM=4 while read LINE; do LINNUM=\`expr \$LINENUM + 1\` done \< smallops.csv FILE=fileA.csv while read LINE; do \#store field 1 F1=\$(echo \$line\|cut -d\$FS -f1) \#store field 2 F2=\$(echo \$line\|cut -d\$FS -f6) \#store field 3 F3=\$(echo \$line\|cut -d\$FS -f7) sed '{\$LINNUM s/lgn/\$F1/g; \$LINNUM s/ssn/\$F2/g; \$LINNUM s/ffn/\$F3/g; }' -i smallops.csv done \< g.csv echo [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48830 "permalink to this comment") - Philippe Petrinko Aug 17, 2010 @ 14:04 @Alvin First, this code won’t work at least because it does not input fileA.csv as intended. Second, to debug, try to break down this program, piece by piece. For instance, it could read input more easily from fileA.csv this way: (I have not included your \[sed\] instruction yet. Go step by step) ``` # backup current IFS (Internal File Separator) IFS_backup="${IFS}" # change IFS to directly read input file into 3 variables a,b,c IFS="," while read a b c do echo "LOGIN:$a LASTNAME:$b FIRSTNAME:$c" done < fileA.csv # restore IFS IFS="${IFS_backup}" ``` Third, try to explain what you would like to do with you \[sed\] instruction. Why do you start your LINENUM at 4? What is the content of your smallops.csv? What is it for? By the way, your \[sed\] instruction seems to contain a mispelled search pattern, for first field \$F1, should’nt it be \[loginn\] instead of \[lgn\] ? You mention only ONE csv file, but your code contains: fileA.csv, smallops.csv, and g.csv ? What are they? Typos ? Errors in your code? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48836 "permalink to this comment") - Philippe Petrinko Aug 17, 2010 @ 14:05 Sorry, (I forgot a HTML code TAG) Complete code is: ``` # backup current IFS (Internal File Separator) IFS_backup="${IFS}" # change IFS to directly read input file into 3 variables a,b,c IFS="," while read a b c do echo "LOGIN:$a LASTNAME:$b FIRSTNAME:$c" done < fileA.csv # restore IFS IFS="${IFS_backup}" ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48837 "permalink to this comment") - firmit Jun 7, 2009 @ 18:03 Excellent! Thanks Vivek. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-41959 "permalink to this comment") - Peko Jul 16, 2009 @ 18:11 Hi Vivek, Thanks for this a useful topic. IMNSHO, there may be something to modify here ======================= Latest bash version 3.0+ has inbuilt support for setting up a step value: \#!/bin/bash for i in {1..5} ======================= 1) The increment feature seems to belong to the version 4 of bash. Reference: <http://bash-hackers.org/wiki/doku.php/syntax/expansion/brace> Accordingly, my bash v3.2 does not include this feature. BTW, where did you read that it was 3.0+ ? (I ask because you may know some good website of interest on the subject). 2\) The syntax is {from..to..step} where from, to, step are 3 integers. You code is missing the increment. Note that GNU Bash documentation may be bugged at this time, because on GNU Bash manual, you will find the syntax {x..y\[incr\]} which may be a typo. (missing the second “..” between y and increment). see <http://www.gnu.org/software/bash/manual/bashref.html#Brace-Expansion> The Bash Hackers page again, see <http://bash-hackers.org/wiki/doku.php/syntax/expansion/brace> seeems to be more accurate, but who knows ? Anyway, at least one of them may be right… ;-) Keep on the good work of your own, Thanks a million. — Peko [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42569 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Jul 16, 2009 @ 18:31 @ Peko, Thanks for pointing out ranges vs step value. I’ve updated the FAQ. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42571 "permalink to this comment") - Peko Jul 16, 2009 @ 20:04 Yes. But you mispelled the syntax with an extra dot “.” after “START’ not {START…END..INCREMENT} but {START..END..INCREMENT} ;-) — Peko [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42574 "permalink to this comment") - Michal Kaut Jul 22, 2009 @ 6:12 Hello, is there a simple way to control the number formatting? I use several computers, some of which have non-US settings with comma as a decimal point. This means that `for x in $(seq 0 0.1 1)` gives 0 0.1 0.2 … 1 one some machines and 0 0,1 0,2 … 1 on other. Is there a way to force the first variant, regardless of the language settings? Can I, for example, set the keyboard to US inside the script? Or perhaps some alternative to `$x` that would convert commas to points? (I am sending these as parameters to another code and it won’t accept numbers with commas…) The best thing I could think of is adding `` x=`echo $x | sed s/,/./` `` as a first line inside the loop, but there should be a better solution? (Interestingly, the sed command does not seem to be upset by me rewriting its variable.) Thanks, Michal [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42668 "permalink to this comment") - Peko Jul 22, 2009 @ 7:27 To Michal Kaut: Hi Michal, Such output format is configured through LOCALE settings. I tried : export LC\_CTYPE=”en\_EN.UTF-8″; seq 0 0.1 1 and it works as desired. You just have to find the exact value for LC\_CTYPE that fits to your systems and your needs. Peko [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42669 "permalink to this comment") - Peko Jul 22, 2009 @ 14:29 To Michal Kaus \[2\] Ooops – ;-) Instead of LC\_CTYPE, LC\_NUMERIC should be more appropriate (Although LC\_CTYPE is actually yielding to the same result – I tested both) By the way, Vivek has already documented the matter : <https://www.cyberciti.biz/tips/linux-find-supportable-character-sets.html> — Peko [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42674 "permalink to this comment") - VIKAS Jul 22, 2009 @ 15:58 Excellent stuff… keep up the good work. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-42676 "permalink to this comment") - Brad Landis Oct 26, 2009 @ 15:26 Comment 12 was really helpful. I was trying to split up a log file by date, such as logfile.20091026 , without having to use grep a million times. I’m kind of disappointed I couldn’t find a one-liner to do so, but I will take what I can get :). [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44327 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Oct 26, 2009 @ 16:47 @Brad, Try this without grep or cut using bash parameter expansion : ``` file="logfile.20091026" log="${file%%.*}" date="${file##*.}" echo $log echo $date ``` HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44328 "permalink to this comment") - Philippe Petrinko Oct 26, 2009 @ 16:52 H i vivek, Just wondering why you don’t amend the typo I pointed out: \<\> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44329 "permalink to this comment") - Brad Landis Oct 26, 2009 @ 16:53 I think you misunderstood. I’m going line by line, and converting the dates at the beginning of the line, such as “Sep 12”, and copying that line from logfile to logfile.20090912. My script is *really* slow though, with the conversion of the month name to a number. I’ve tried using the date command, and my own function, and both take 7 seconds to process 10,000 lines. It doesn’t seem like a long time, but I’ve got a lot of log files to process on multiple machines. I don’t guess you’d know a faster trick, would you? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44330 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Oct 26, 2009 @ 18:37 @Brad, yes, I did misunderstood your post. If I were you I will try out awk. @Philippe, Thanks for the heads up. The faq has been updated. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44333 "permalink to this comment") - TheBonsai Oct 30, 2009 @ 6:13 @Peko: (I’m the operator of bash-hackers.org/wiki, that’s why I found this page): Regarding Bash documentation for brace expansion (increment syntax), actually I’m right and the documentation is wrong (a rare situation!). I reported it to the list. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44377 "permalink to this comment") - Philippe Petrinko Oct 30, 2009 @ 8:35 To Vivek: Regarding your last example, that is : running a loop through arguments given to the script on the command line, there is a simplier way of doing this: \# instead of: \# FILES=”\$@” \# for f in \$FILES \# use the following syntax for arg do \# whatever you need here – try : echo “\$arg” done Of course, you can use any variable name, not only “arg”. To TheBonsai: Welcome Buddy\! Fine! I am happy to see 2 great FOSS web sites now related \! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44380 "permalink to this comment") - tdurden Nov 10, 2009 @ 21:32 Command line while loop.. Very handy.. Say you wanted to rename all the files in a specific dir.. Create a file with the contents you want to rename (ls -l \| awk ‘{print \$9}’ \> asdf or something) Contents of asdf: file1 file2 file3 file4 cat asdf \| while read a ; do mv \$a \$a.new ; done ls -l asdf file1.new file2.new file3.new file4.new I have used this while command for many things from simply renaming files to formatting and labling new SAN luns.. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44573 "permalink to this comment") - Dr. Stefan Gruenwald Apr 1, 2011 @ 4:00 There are much easier ways to do this – also it works only for extensions. How do you change the middle of the file name or a few characters on the left? Here is the regular way of what you just did: for i in \*; do mv \$i \$i.new; done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56882 "permalink to this comment") - TheBonsai Nov 11, 2009 @ 7:07 There are 2 problems and one optical flaw with your code: (1) You should use read -r without any variable name given, to use the default \$REPLY (due to a specific behaviour of read, see manpage) (2) You should quote \$a (3) Useless use af cat :) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44582 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 11:25 To tdurden: Why would’nt you use 1\) either a \[for\] loop for old in \* ; do mv \${old} \${old}.new; done 2\) Either the \[rename\] command ? excerpt form “man rename” : RENAME(1) Perl Programmers Reference Guide RENAME(1) NAME rename – renames multiple files SYNOPSIS rename \[ -v \] \[ -n \] \[ -f \] perlexpr \[ files \] DESCRIPTION “rename” renames the filenames supplied according to the rule specified as the first argument. The perlexpr argument is a Perl expression which is expected to modify the \$\_ string in Perl for at least some of the filenames specified. If a given filename is not modified by the expression, it will not be renamed. If no filenames are given on the command line, filenames will be read via standard input. For example, to rename all files matching “\*.bak” to strip the extension, you might say rename ‘s/\\.bak\$//’ \*.bak To translate uppercase names to lower, you’d use rename ‘y/A-Z/a-z/’ \* — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44585 "permalink to this comment") - TheBonsai Nov 11, 2009 @ 11:49 Note for rename(1): There exist two major variants on Linux system. One non-Perl originating in the RedHat area, and one Per, originating in the Debian area. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44586 "permalink to this comment") - Sean Nov 11, 2009 @ 14:42 To tdurden: I would also replace “ls -l \| awk ‘{print \$9}'” with just “ls”. Otherwise you’ll run into issues with files that have spaces in it. As far as using: for i in \*; vs for i in \$(ls); I personally prefer “\$(ls)” or “\$(find . )”. This provides more control over what files I’m going to be looping through. For instance: \$(ls -F \| grep -v “\\/\$”) or \$(ls -A) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44591 "permalink to this comment") - A.R.Memon Dec 4, 2012 @ 9:58 \#!/bin/bash echo “Bash version \${BASH\_VERSION}…” for i in {0..10..2} do echo “Welcome to my new script \$i times” done help ……………………….. :) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-74651 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 15:03 To Sean: CMIIAW : try the following commands: \# touch “file with spaces in name” \# for f in \*; do echo “”;done … … which shows that there is no need to use \[for f in \$(ls)\] instead of \[ for f in \*\] Doesn’t it ? — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44593 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 15:14 Sorry Sean, my last post was truncated, due to limitations of this form used to post comments. (impossible to use Greater\_than and Less\_than caracters) I meant, use the following: \# touch “file with spaces in name” \# for f in \*; do echo “:\${f}:”;done … :file with spaces in name: … [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44594 "permalink to this comment") - Sean Nov 11, 2009 @ 20:10 Sorry for the confusion, I understand that “for i in \*;” will not have any issues with spaces. I was referring to the ls -l \| awk ‘{print \$9}’ having issues with spaces. The reason I choose to use \$(ls) instead of \* is for filtering out unwanted files e.g. \$(ls -F \| grep -v “\\/\$”) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44602 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 21:16 To Sean: But then, that’s wrong. \[ for f in \$(ls -F\|grep -v “V\$”) \] won’t process appropriately spaces in filename. Check : \# touch “file with spaces in name” \# for f in \$(ls -F\|grep -v “V\$”); do echo “:\${f}:”;done :file: :with: :spaces: :in: :name: [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44604 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 21:18 The best tool to filter files and process them is \[find\] piped to \[xargs\] (with zero-ended filenames) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44605 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 21:25 To sean: But if you want to exclude files from globbing, \[bash\] has the \[extglob\] option. Let’s say you want to process every file except files ending by a “V”, just type \# for f in !(\*V); do echo “:\${f}:”;done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44606 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 21:27 If you set the shell option extglob, Bash understands some more powerful patterns. Here, a is one or more pattern, separated by the pipe-symbol (\|). ?() Matches zero or one occurrence of the given patterns \*() Matches zero or more occurrences of the given patterns +() Matches one or more occurrences of the given patterns @() Matches one of the given patterns !() Matches anything except one of the given patterns [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44607 "permalink to this comment") - Philippe Petrinko Nov 11, 2009 @ 21:28 source: <http://www.bash-hackers.org/wiki/doku.php/syntax/pattern> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44608 "permalink to this comment") - Narender Nov 12, 2009 @ 6:47 I have two files here X.a and y.a Now what i need is i need to substitute CvfdsDisk\_sdb/c/d/e in lines of Node CvfsDisk\_XXX in the order CvfsDisk\_sdb/c/f/g first word of each line of x.a exists. how can i do in shell scripting i can get the first word of each line of X.a using awk /cut but to replace these in y.a i am not getting it … any help here ? \[Raj\]\$ cat x.a CvfsDisk\_sdb /dev/sdb \# host 0 lun 1 sectors 4840746976 sector\_size 512 inquiry \[AMCC 9550SX-12M DISK 3.08\] serial AMCC ZAJBSXJFF92A9D003C6A CvfsDisk\_sdc /dev/sdc \# host 0 lun 0 sectors 3906148319 sector\_size 512 inquiry \[AMCC 9550SX-12M DISK 3.08\] serial AMCC ZAJ8MJKFF92A9D001FEC CvfsDisk\_sdf /dev/sdf \# host 0 lun 1 sectors 4840746976 sector\_size 512 inquiry \[AMCC 9550SX-12M DISK 3.08\] serial AMCC ZAJBSXJFF92A9D003C6A CvfsDisk\_sdg /dev/sdg \# host 0 lun 0 sectors 3906148319 sector\_size 512 inquiry \[AMCC 9550SX-12M DISK 3.08\] serial AMCC ZAJ8MJKFF92A9D001FEC \[naren@Beas dxall\]\$ cat y.a \[StripeGroup Metafiles\] Metadata Yes Status UP Read Enabled Write Enabled Journal Yes StripeBreadth 1280K Node CvfsDisk\_sdb 0 \[StripeGroup datafiles1\] Metadata Yes Status UP Read Enabled Write Enabled StripeBreadth 1024K Node CvfsDisk\_sdc 0 \[StripeGroup datafiles2\] Metadata Yes Status UP Read Enabled Write Enabled StripeBreadth 1280K Node CvfsDisk\_sdd 0 \[StripeGroup datafiles3\] Metadata Yes Status UP Read Enabled Write Enabled StripeBreadth 1024K Node CvfsDisk\_sde 0 [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44615 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Nov 12, 2009 @ 13:47 @Narender, Your post is offtopic. I suggest you use our shell scripting [forum](http://nixcraft.com/) for question. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44628 "permalink to this comment") - Sean Nov 12, 2009 @ 15:26 To Philippe: You are right, \# for i in \$(ls) will break up files with spaces if IFS isn’t set to just the newline character. I don’t believe this is consistent across distributions. So the for loop should have \# export IFS=\$’\\n’ before it. I also use find in for loops when I want to look through the directory contents, but this isn’t always desired. Thanks for the info about extglob, I haven’t done much with extended globbing in bash. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44631 "permalink to this comment") - Philippe Petrinko Nov 12, 2009 @ 15:44 To Sean: Right, the more sharp a knife is, the easier it can cut your fingers… I mean: There are side-effects to the use of file globbing (like in \[ for f in \* \] ) , when the globbing expression matches nothing: the globbing expression is not susbtitued. Then you might want to consider using \[ nullglob \] shell extension, to prevent this. see: <http://www.bash-hackers.org/wiki/doku.php/syntax/expansion/globs#customization> Devil hides in detail ;-) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-44632 "permalink to this comment") - The\_Catalanish Dec 4, 2009 @ 11:22 Response to the tip number 12 At thos script, It’s missing the followng line FS=’:’ in the variables declaration (you forgit the delimiter field, for the cut command) :-P The\_Catalanish [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45023 "permalink to this comment") - Rilif Dec 10, 2009 @ 21:27 \#! /usr/bin/ksh for i in \`cat /input\` do bdf \| grep file\_system \| grep -vE ‘^A\|B\|C’ \| awk ‘{ print \$4}’ \| while read output; do file\_system=\$(echo \$output \| awk ‘{ print \$1}’ \| cut -d’%’ -f1 ) partition=\$(echo \$output \| awk ‘{ print \$2 }’ ) if \[ \$file\_system -ge 60 \]; then echo “don’t run the sync \$partition (\$file\_system%) ” else rsync \$i fi done done The problem with the logic I’m having is I do not want the script to exit(as it does now) the loop once the file\_system area reaches 60%. I want it to continue to retest bdf and continue the loop once disk usage drops below 60%. Any Ideas? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45121 "permalink to this comment") - Philippe Petrinko Dec 11, 2009 @ 12:17 To Rilif: 1\) I assume you use \[ bdf \] on UNIX system – because Linux equivalent is \[ df \] – and I cannot be of help because I cannot test your script on my Linux boxes. 2\) This seems to be a specific programming debugging problem and out of this topic scope – There may be a better place to post that kind of topic – A programmer forum for instance. Best regards. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45131 "permalink to this comment") - dee Dec 13, 2009 @ 10:27 do any one know how to write this script in steps? as so /// ./ test 10 /// The first argument \[1\] will ex. to create a multiple users, groups, cn, dn, etc for ldap in one or two scripts but from command line. you would just enter file then the number of atrributes to build. this is a headache for me since i’m new at this. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45150 "permalink to this comment") - Philippe Petrinko Dec 13, 2009 @ 10:54 To Dee: 0\) The first part of your first sentence is incomprehensible – this may be because text that you entered is altered, it may contain HTML-like syntax that is interpreted by this comment form. (By the way, Vivek Gite would be welcomed to tell us how to prevent this. TIA :-) ) 1\) LDAP syntax is off-topic. 2\) You’ll find appropriate resources in LDAP forums/sites – just find out. 3\) We may be in position to help you to build a \[for\] loop, assuming you do your part of the job by providing the basic LDPA instructions to create user, for instance. Try to create at least a LDAP object by yourself on the command-line, then provide us the code, and as much as possible further explanation please. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45151 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Dec 13, 2009 @ 10:58 There was no html tag or anything else in comment. @dee, if you need to attach code use \<pre\> tags. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45152 "permalink to this comment") - Philippe Petrinko Dec 13, 2009 @ 11:44 Thanks Vivek – But I am afraid I do not get it right – what does “pre” mean ? (I understand you wrote the “less than” tag, and “greater than” tag – but why “pre” ? And are you sure these are the only ones two use ? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45153 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Dec 13, 2009 @ 13:26 @Philippe, All allowed html tags are displayed below the form itself. It is wordpress that converts those symbol and syntax is ``` <pre>#!/bin/bash echo "Hello world!" </pre> ``` HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45154 "permalink to this comment") - dee Dec 13, 2009 @ 13:41 first file make: create\_user\_idif.sh.txt ``` #!/bin/bash echo "dn: $2 $3,o=dmacc,dc=bad1dee,dc=com" > $1 echo "changetype: add" >> $1 echo "objectclass: top" >> $1 echo "objectclass: person" >> $1 echo "objectclass: organizationalPerson" >> $1 echo "objectclass: inetOrgPerson" >> $1 echo "cn: $2 $3" >> $1 echo "givenName: $2" >> $1 echo "sn: $3" >> $1 echo "uid: ${2:0:1}$3" >> $1 echo "mail: $4" >> $1 ___________________________________ mass_user.txt Scott,brown,sbrown@bad4dee.com\n karla,smith,ssmith@bad4dee.com\n sam,goodie,sgoodie@bad4dee.com\n marge,jones,mjones@bad4dee.com ____________________________________ mass_add.sh.txt #!/bin/bash u1=`cat $1 | tr -d '\n'` #u2=`echo $u1 | tr \| '\n'` u2=`echo $u1 | sed s/\|/\\n/` echo "DBG" echo -e $u1 echo "DBG" echo -e $u1 | ( IFS=, ; while read fname lname mail; do echo -e "Creating $fname $lname\n\n" ``` ./create\_user\_ldif.sh.txt ./user.ldif \$fname \$lname \$mail ``` cat ./user.ldif echo -e "\n\n" done ) ``` \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ ./mass\_add.sh.txt mass\_user.txt This ex: will pull from a list but same out come i do not know how to write another script to pull the attributes i need from the command line like ./test 100 and that command will pull only a 100 users id’s from idif.txt out of 1000 generated. This next samples of code will file in the attributes for you. first file make: create\_user\_idif.sh.txt ``` #!/bin/bash echo "dn: $2 $3,o=dmacc,dc=bad1dee,dc=com" > $1 echo "changetype: add" >> $1 echo "objectclass: top" >> $1 echo "objectclass: person" >> $1 echo "objectclass: organizationalPerson" >> $1 echo "objectclass: inetOrgPerson" >> $1 echo "cn: $2 $3" >> $1 echo "givenName: $2" >> $1 echo "sn: $3" >> $1 echo "uid: ${2:0:1}$3" >> $1 echo "mail: $4" >> $1 ``` \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Then: mass\_add.sh.txt ``` #!/bin/bash u1=`cat $1 | tr -d '\n'` #u2=`echo $u1 | tr \| '\n'` u2=`echo $u1 | sed s/\|/\\n/` echo "DBG" echo -e $u1 echo "DBG" echo -e $u1 | ( IFS=, ; while read fname lname mail; do echo -e "Creating $fname $lname\n\n" ./create_user_ldif.sh.txt ./user.ldif $fname $lname $mail cat ./user.ldif echo -e "\n\n" done ) ``` \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ last: adduserfile1.txt ``` user0,boo,us1@bad1dee.com\n user1,boo,us1@bad1dee.com\n user2,boo,us1@bad1dee.com\n user3,boo,us1@bad1dee.com\n user4,boo,us1@bad1dee.com\n user5,boo,us1@bad1dee.com\n ./mass_add.sh.txt adduserfile1.txt ``` This is what i’m working on now ? i still do not know how to tie in C++ or bash script this code to work with command line, so i can control the out come of created users. ``` #!/bin/bash Set objRootDSE = GetObject("LDAP://rootDSE") Set objContainer = GetObject("LDAP://cn=Users," & _ objRootDSE.Get("defaultNamingContext")) For i = 1 To 1000 Set objLeaf = objContainer.Create("User", "cn=UserNo" & i) objLeaf.Put "sAMAccountName", "UserNo" & i objLeaf.SetInfo Next WScript.Echo "1000 Users created." example: [root]#./test 10 usid:UserNo1 gid:manager cn:Bob dn:bHarison UserNo2 UserNo3 ^^^^^^^ UserNo10 ``` This script makes a 1000 users. However i can not control the out come. For example: from the command line I would like it to stop at 100 users by typing in ./test 100. Using agrv \[1\]. so when I type a number after the file name it will create a list and print that record to the screen. I do not know bash that well as C++ and it is not helping because the char.. are diff… Edited by admin. Reason: *This is not a forum, this is a blog. If you need further help please try our forum @nixcraft.com.* [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45155 "permalink to this comment") - Philippe Petrinko Dec 13, 2009 @ 14:51 To Dee: 1) Man, with a 3-users-sample instead of hundreds, we would have figured out, don’t you think so? 2\) Well that’s a start. May be Vivek would like to wipe this post out, and create a new topic: “Of mice, LDAP and loops” ;-) ??? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45160 "permalink to this comment") - Dominic Jan 14, 2010 @ 10:04 There is an interesting difference between the exit value for two different for looping structures (hope this comes out right): You see that the first structure does a final increment of c, the second does not. The first is more useful IMO because if you have a conditional break in the for loop, then you can subsequently test the value of \$c to see if the for loop was broken or not; with the second structure you can’t know whether the loop was broken on the last iteration or continued to completion. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45560 "permalink to this comment") - Dominic Jan 14, 2010 @ 10:09 sorry, my previous post would have been clearer if I had shown the output of my code snippet, which is: [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-45561 "permalink to this comment") - Dmitry Mar 8, 2010 @ 17:47 What if I would like to put everything into one line? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46292 "permalink to this comment") - Dominic Mar 9, 2010 @ 5:29 Dmitry, please give a little more detail about what you are trying to achieve. You can see from my examples above that there is no problem to put a simple loop on one line. Basically you use semicolons (;) instead of line breaks. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46297 "permalink to this comment") - Dmitry Mar 9, 2010 @ 13:56 Dominic, thaks a lot for your quick answer. You have answered on my question but I’m still having problems. Please take a look at this. dmitry@elastix-laptop:~/projects\_cg/match\_delays/source\$ for i in \$(seq 1 2 20) \> do \> echo “Welcome \$i times” \> done Welcome 1 times Welcome 3 times Welcome 5 times Welcome 7 times Welcome 9 times Welcome 11 times Welcome 13 times Welcome 15 times Welcome 17 times Welcome 19 times dmitry@elastix-laptop:~/projects\_cg/match\_delays/source\$ for i in \$(seq 1 2 20); do; echo “Welcome \$i times” ; done bash: syntax error near unexpected token \`;’ dmitry@elastix-laptop:~/projects\_cg/match\_delays/source\$ What am I missing here? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46303 "permalink to this comment") - Philippe Petrinko Mar 9, 2010 @ 14:05 @Dmitry You are missing : Reading The Fantastic Manual. :-) There should not be any “;” following the \[do\]. Good ol’ one: “When any thing goes wrong – (re) Read the manual” [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46304 "permalink to this comment") - Philippe Petrinko Mar 9, 2010 @ 14:34 @Dmitry And, again, as stated many times up there, using \[seq\] is counter productive, because it requires a call to an external program, when you should Keep It Short and Simple, using only bash internals functions: (and I wonder why Vivek is sticking to that old solution which should be presented only for historical reasons when there was no way of using bash internals. By the way, this historical recall should be placed only at topic end, and not on top of the topic, which makes newbies sticking to the not-up-to-date technique ;-) ) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46306 "permalink to this comment") - Dmitry Mar 9, 2010 @ 14:49 Philippe, thank you, all works perfect know. Here is the partial excuse that I was reading this thread instead of bash manual [http://www.google.es/search?q=bash+for+loop\&ie=utf-8\&oe=utf-8\&aq=t\&rls=com.ubuntu:en-US:official\&client=firefox-a](https://www.google.es/search?q=bash+for+loop&ie=utf-8&oe=utf-8&aq=t&rls=com.ubuntu:en-US:official&client=firefox-a) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46307 "permalink to this comment") - Dominic Mar 9, 2010 @ 15:23 It is strangethat a do/done loop works if there is CR (end of line) after the do, but not if there is a semi-colon. I can see why this was confusing for you Dmitry, because it’s not logical. My guess is that the acceptance of CR after do was added because people wanted to lay out code this way, but the bash coders forgot to allow the semicolon alternative. As Philippe points out, if you follow the manual strictly, it works fine. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46308 "permalink to this comment") - Dmitry Mar 9, 2010 @ 15:27 Ok. Thank you again\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46309 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Mar 9, 2010 @ 17:30 @Philippe, I’ve just updated the faq and also deleted large data sample posted by dee user. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46312 "permalink to this comment") - TheBonsai Mar 9, 2010 @ 17:55 @ Dominic Yes, it’s not quite intuitive, right. What you mean is the semicolon or the newline as list separator (list as the grammar construct defined in the manual, respectively by ISO9945). After a \`do’, a list is expected, but a list isn’t **introduced** with a list separator. After a \`do’, the shell awaits more input, just like after an opening quote character. In interactive mode, it also displays the continuation prompt \`PS2′ instead of \`PS1′ (it would display \`PS1′ for list continuation). It’s not right that the Bash coders “forgot” it. Inspecting the grammar rules of POSIX XCU Sec. 2.10.2 doesn’t show a special rule here (it would have to be a special exceptional rule that extra allows a semicolon here). [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46314 "permalink to this comment") - TheBonsai Mar 9, 2010 @ 18:06 Me again. From all Bourne-like shells I just “tested”, only ZSH seems to support a semicolon as a start of a list (also in the case after the \`do’). This is nice, but that’s all. It’s not a bug to not do so. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46316 "permalink to this comment") - Dominic Mar 9, 2010 @ 18:54 @ TheBonsai Interesting. I accept that it is not a bug, but I still think it is confusing. It seems logical to us lesser mortals that in bash semicolon=newline, and in other situations I think this is true, but not here. ``` #any number of blank lines or even comments ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46317 "permalink to this comment") - Philippe Petrinko Mar 9, 2010 @ 23:10 @Dominic You are missing the point. If you read our Unix pioneers, you will remember: – Rule of Optimization: Prototype before polishing. Get it working before you optimize it. \[E. Raymond\] see [http://en.wikipedia.org/wiki/Unix\_philosophy](https://en.wikipedia.org/wiki/Unix_philosophy) What’s the point of spending hours to code on one line? – First, It does not give any optimization, it does not save any execution time. Your code will only be more difficult to read, check, debug. Defensive programming rules include this: Write one instruction per line. – Second, You still wanna code all on one line ? Big deal. The manual gave you the right way. So stick to it, or leave it, and skip to the next real problem, instead of wasting time and energy pointlessly, my dear Linux enthusiast. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46319 "permalink to this comment") - Sean Mar 9, 2010 @ 23:15 I have a comment to add about using the builtin **for (( … ))** syntax. I would agree the builtin method is cleaner, but from what I’ve noticed with other builtin functionality, I had to check the speed advantage for myself. I wrote the following files: builtin\_count.sh: seq\_count.sh: And here were the results that I got: time ./builtin\_count.sh real 0m22.122s user 0m18.329s sys 0m3.166s time ./seq\_count.sh real 0m19.590s user 0m15.326s sys 0m2.503s The performance increase isn’t too significant, especially when you are probably going to be doing something a little more interesting inside of the for loop, but it does show that builtin commands are not necessarily faster. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46320 "permalink to this comment") - Andi Reinbrech Nov 18, 2010 @ 20:35 The reason why the external seq is faster, is because it is executed only once, and returns a huge splurb of space separated integers which need no further processing, apart from the for loop advancing to the next one for the variable substitution. The internal loop is a nice and clean/readable construct, but it has a lot of overhead. The check expression is re-evaluated on every iteration, and a variable on the interpreter’s heap gets incremented, possibly checked for overflow etc. etc. Note that the check expression cannot be simplified or internally optimised by the interpreter because the value may change inside the loop’s body (yes, there are cases where you’d want to do this, however rare and stupid they may seem), hence the variables are volatile and get re-evaluted. I.e. botom line, the internal one has more overhead, the “seq” version is equivalent to either having 1000000 integers inside the script (hard coded), or reading once from a text file with 1000000 integers with a cat. Point being that it gets executed only once and becomes static. OK, blah blah fishpaste, past my bed time :-) Cheers, Andi [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-50962 "permalink to this comment") - Philippe Petrinko Nov 18, 2010 @ 21:06 @Andi \> OK, blah blah fishpaste, past my bed time :-) Interesting comments anyway\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-50966 "permalink to this comment") - Philippe Petrinko Mar 10, 2010 @ 9:13 @Sean 1) Again, when your only programming concern that last will be the optimization of your loops, you could invest time into such timings. This would be when there are no other bugs in your code, which I wish you to enjoy ASAP. 2\) But then you may find that the real problem/bottleneck is not a for loop. As Rob Pike said : “Measure. Do not tune for speed until your performance analysis tool tells you which part of the code overwhelms the rest.” \[ [http://en.wikipedia.org/wiki/Unix\_philosophy\#Pike:\_Notes\_on\_Programming\_in\_C](https://en.wikipedia.org/wiki/Unix_philosophy#Pike:_Notes_on_Programming_in_C) \] 3\) I agree with you when you say that your code is not relevant as a timing of real-sized programs. 4\) Relating to your benchmark “builtin vs. external” commands test the builtin \[ for i in {1..1000000} \] and you will see that it is very close to \[for i in \$(seq 1 1000000)\] [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46330 "permalink to this comment") - 2012 Doom Day Mar 10, 2010 @ 19:01 > You are missing : Reading The Fantastic Manual. :-) A.. uh.. ? The lack of examples in the bash man page is the main reason to \*avoid\* man page. Everyone, knowns how to use them. Syntax is all good, only if you know the bash and UNIX in and out. This is the main reason why most people purchase bash and shell scripting books from O’reilly or Amazon. Rest of freeloaders depends upon Google and site like this to get information quickly. man pages are for gurus; for all new user examples are the best way to get started. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46334 "permalink to this comment") - Philippe Petrinko Mar 10, 2010 @ 21:31 @ 2012DD I agree – I use any of resource I need, man page, –help page, info page, web pages, books. The thing is: you should try to read man page once. And actually, if he did, he would have find the syntax. Vivek’s web site and contributions do not prevent you of reading the “fantastic” manual. And, as usual, the ones that issue the bitter critics will not move a finger to enhance the manual. You say man page lacks good examples? Did you ever try to contribute to any man pages ? Hope you did. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46336 "permalink to this comment") - TheBonsai Mar 11, 2010 @ 11:30 The Bash manual page isn’t meant as tutorial. It’s a syntax, grammar and behaviour reference. However, it contains the knowledge to explain why a for loop using \`seq’, one using brace expansion and one using builtin arithmetics have the performance relations they actually show when you execute them. The point is to make a relation between abstract descriptions and real execution behaviour. If such things really count, however, I suspect you code in the wrong language. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46347 "permalink to this comment") - Philippe Petrinko Mar 13, 2010 @ 21:50 @Bonsai \> The Bash manual page isn’t meant as tutorial. It’s a syntax, grammar and behaviour reference. Actually, no. A man page can/should contain a EXAMPLE section. check : [http://en.wikipedia.org/wiki/Man\_page\#Layout](https://en.wikipedia.org/wiki/Man_page#Layout) I am pretty happy when the Example section is relevant. And when you want some more, nothing prevents you to try to add new examples… Let’s contribute\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46406 "permalink to this comment") - TheBonsai Mar 14, 2010 @ 0:34 @Philippe How many examples would you place there, to show the “common usage of Bash”? I agree that manpages usually should contain examples, but I think this would be too much. Huge manpages (huge because they describe a huge set of functionality) contain very small/no examples. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46407 "permalink to this comment") - 2012 Doom Day Mar 14, 2010 @ 5:39 @Philippe, I am learning Bash scripting and that is why I’m here and its wiki. Take a look at Solaris UNIX man page, most of them have good set of examples. Another candidate is FreeBSD, they also have good set of examples. Just discovered that our HP-UX came with printed “Posix Born Shell Scripting Manual”. \>Did you ever try to contribute to any man pages ? No, I’m learning and if I \*contribute\* anything, I’m dam sure most shell scripting gurus will eat me alive, as I’m not experienced coder. Once I tried to help someone on comp.unix.shell and most of other people on list were so mean to my code that I almost stopped visiting comp.unix.shell. \*Beep\* those bastards\! *Edited by admin* [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46410 "permalink to this comment") - TheBonsai Mar 19, 2010 @ 5:21 @2012 Doom Day Contribution is more than just knowing code. Alone the fact that you write here is a contribution (to the community). Translations, documentation, searching bugs, helping others, sharing expiriences, … [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46500 "permalink to this comment") - Philippe Petrinko Mar 19, 2010 @ 8:35 Quite right, Bonsai, and you can contribute to Wikibooks, Wikipedia, and Vivek’s Wiki using the books you own and all you have learnt, no one will ever prevent you of doing so, assuming you improve the content. Don’t be shy and be confident on your capacities. See, I wrote loads of questionable comments and Vivek has not banned me \[yet\] ;-). [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46503 "permalink to this comment") - Chris Cheltenham Apr 2, 2010 @ 19:33 Do you know why this doesn’t output anything? \#!/bin/bash for i in \$(cat /\$HOME/client\_list.txt) do echo \$i \> /home/\$i\_file.log done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46713 "permalink to this comment") - Philippe Petrinko Apr 2, 2010 @ 20:47 @Chris C If you want a good explanation, first try to ask a good question and explain: 1a) What you want to do with this program 1b) what your program is supposed to do. Second: Mainly, it will fail because there will not be variable expansion \$i\_file.log should be \${i}\_file.log Read again about variable expansion. And: 2a) in your ” cat “, there should not be a leading slash before \$HOME (because \$HOME contains a leading slash) – anyway this wont prevent it from working – but may come to bugs someday. 2c) if a line in client\_list.txt does contains spaces, what do you think this would do? Use quotes. 2d) If it still fails, check your permissions to create and overwrite a file in “/home” directory 2e) As said many times, you do not need to use ” for + cat ” to use the content of a file. Just use a while loop : [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-46714 "permalink to this comment") - Moihan May 9, 2010 @ 11:36 Sir, This is a new post. From a file in unix server with a column of temperature, I want to extract a number if it goes greater than 100. Normally it will be in 60 – 80 range. Can u suggest a bash script? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47254 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) May 9, 2010 @ 13:00 Use our shell scripting forum [for questions](http://nixcraft.com/shell-scripting/). [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47255 "permalink to this comment") - Anthony Thyssen Jun 4, 2010 @ 6:53 The {1..10} syntax is pretty usless as you can use a variable with it\! ``` limit=10 echo {1..${limit}} {1..10} ``` You need to eval it to get it to work\! ``` limit=10 eval "echo {1..${limit}}" 1 2 3 4 5 6 7 8 9 10 ``` ‘seq’ is not avilable on ALL system (MacOSX for example) and BASH is not available on all systems either. You are better off either using the old while-expr method for computer compatiblity\! ``` limit=10; n=1; while [ $n -le 10 ]; do echo $n; n=`expr $n + 1`; done ``` Alternativally use a seq() function replacement… ``` # seq_count 10 seq_count() { i=1; while [ $i -le $1 ]; do echo $i; i=`expr $i + 1`; done } # simple_seq 1 2 10 simple_seq() { i=$1; while [ $i -le $3 ]; do echo $i; i=`expr $i + $2`; done } seq_integer() { if [ "X$1" = "X-f" ] then format="$2"; shift; shift else format="%d" fi case $# in 1) i=1 inc=1 end=$1 ;; 2) i=$1 inc=1 end=$2 ;; *) i=$1 inc=$2 end=$3 ;; esac while [ $i -le $end ]; do printf "$format\n" $i; i=`expr $i + $inc`; done } ``` Edited: by Admin – added code tags. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47634 "permalink to this comment") - Philippe Petrinko Jun 4, 2010 @ 7:34 @Anthony. Quite right – braces {start..end..step} might not be the best thing in bash. Nevertheless, I still stick to the old C-like synxtax in a for loop, which does accept variable arguments, such as: I don’t know much of this FOR loop syntax portability, functions you suggest may be the best thing to use for portability concern. (I have to read POSIX reference again :-) ) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47635 "permalink to this comment") - TheBonsai Jun 4, 2010 @ 9:57 The Bash C-style for loop was taken from KSH93, thus I guess it’s at least portable towards Korn and Z. The seq-function above could use i=\$((i + inc)), if only POSIX matters. expr is obsolete for those things, even in POSIX. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47636 "permalink to this comment") - Philippe Petrinko Jun 4, 2010 @ 10:15 Right Bonsai, ( <http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_04> ) But FOR C-style does not seem to be POSIXLY-correct… Read on-line reference issue 6/2004, Top is here, <http://www.opengroup.org/onlinepubs/009695399/mindex.html> and the Shell and Utilities volume (XCU) T.OC. is here <http://www.opengroup.org/onlinepubs/009695399/utilities/toc.html> doc is: <http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap01.html> and FOR command: <http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_04_03> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47637 "permalink to this comment") - Anthony Thyssen Jun 6, 2010 @ 7:18 TheBonsai wrote…. “The seq-function above could use i=\$((i + inc)), if only POSIX matters. expr is obsolete for those things, even in POSIX.” I am not certain it is in Posix. It was NOT part of the original Bourne Shell, and on some machines, I deal with Bourne Shell. Not Ksh, Bash, or anything else. Bourne Shell syntax works everywhere! But as ‘expr’ is a builtin in more modern shells, then it is not a big loss or slow down. This is especially important if writing a replacement command, such as for “seq” where you want your “just-paste-it-in” function to work as widely as possible. I have been shell programming pretty well all the time since 1988, so I know what I am talking about! Believe me. MacOSX has in this regard been the worse, and a very big backward step in UNIX compatibility. 2 year after it came out, its shell still did not even understand most of the normal ‘test’ functions. A major pain to write shells scripts that need to also work on this system. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47658 "permalink to this comment") - TheBonsai Jun 6, 2010 @ 12:35 Yea, the question was if it’s POSIX, not if it’s 100% portable (which is a difference). The POSIX base more or less is a subset of the Korn features (88, 93), pure Bourne is something “else”, I know. Real portability, which means a program can go wherever UNIX went, only in C ;) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47662 "permalink to this comment") - TheBonsai Jun 4, 2010 @ 17:57 I’ve read the standard ;-) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47645 "permalink to this comment") - Phil Goetz Jun 17, 2010 @ 17:38 That {1 .. N} syntax doesn’t work with current Linux bash. \$for r in {1 .. 15}; do echo \$r; done {1 .. 15} [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47890 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Jun 17, 2010 @ 17:57 Yes, it does works, you need bash version 3.0 or up. Just tested with “GNU bash, version 4.1.5(1)-release (i486-pc-linux-gnu)”. You need to remove white space between 1 and 15, try: ``` for r in {1..15}; do echo $r; done ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47893 "permalink to this comment") - Anthony Thyssen Jun 18, 2010 @ 0:49 I gave some ‘seq’ alternatives, some simple, some more complex, mostly using shell built-ins only, depending on you needs. At the very start of the comments “jot” was mentioned as an alternative, though it does not appear to be as wide spread as “seq”. Anyone know if it is on the ‘limited shell suport’ MacOSX? There are also however some other — off the wall — methods of generating a list of number, or just a list for looping ‘N’ times. One of the weirdest ones I came across was using /dev/zero and “dd”\! dd 2\>/dev/null if=/dev/zero bs=10 count=1 \| tr \\ \\12 \| cat -n \| tr -d ‘\\40\\11′ This gets ’10’ null characters, converts them to line feeds, uses cat to convert them to numbers, and just to clean up, you can optionally delete the tabs and spaces. As I said real odd ball. Like I often say… There are lots of ways to skin a cat, and what method you use depends on what you want that skin for, and how messy you like the results\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47905 "permalink to this comment") - Philippe Petrinko Jun 18, 2010 @ 7:01 Yes, but the code we see won’t work. I think it needs some syntax enhancement in your first \[ tr \], such as: [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47914 "permalink to this comment") - Philippe Petrinko Jun 18, 2010 @ 7:02 Hell ! missed again – I hate that \$%@ Wordpress text entry [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-47915 "permalink to this comment") - Paddy Jul 20, 2010 @ 20:54 Hi guys Ive been reading this thread cos i need some advice on a script. I need to rename some (lots) of files in a directory. they are named.. file\_name.001.01 file\_name.002.01 file\_name.003.01… etc How can I change the names of the files to remove the ‘.01’ at the end of each filename? Im useing Ubuntu Lynx…. Ive been playing with a few examples from this thread, but cant seem to make it work. Any help is appreciated [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48441 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Jul 20, 2010 @ 21:12 Try [rename command](https://www.cyberciti.biz/tips/renaming-multiple-files-at-a-shell-prompt.html): ``` rename 's/\.01$//' *.01 ``` If you must use for: ``` for i in *.01; do mv "$i" "${i%%.01}"; done ``` HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48442 "permalink to this comment") - Dr. Stefan Gruenwald Apr 1, 2011 @ 4:53 In general, if you want to add a suffix to your files, do this (.txt in this example): ls file1 file2 file3 for i in \*; do mv \$i \$i.txt; done ls file1.txt file2.txt file3.txt If you want to take it back off (.txt in this example again) for i in \*.txt; do mv \$i \${i%.\*}; done ls file1 file2 file3 [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56890 "permalink to this comment") - maxy-millianne Jan 24, 2012 @ 6:18 Of course, if you want to worry about files with spaces in (and other things?), put quote around the arguments to mv, as in the gp. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-67483 "permalink to this comment") - Anthony Thyssen Jan 27, 2012 @ 7:48 Note that is you want to append a string that does not start with a ‘.’ (for example the string “\_info.txt”) then you need to delimit the variable name…. for i in \*; do mv “\$i” “\${i}\_info.txt”; done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-67619 "permalink to this comment") - Sapia Jul 29, 2010 @ 6:20 Hi, I have two files that contain diffrent columns. Both files have matching one column but raw oder is different. I want to combine these two files as below. File 1: file 2 x 2 7 123 r 3 5 9 y 3 -8 124 y 4 6 20 z 4 -2 34 q 3 5 70 q 5 -9 5 z 5 4 10 r 6 1 6 x 50 3 40 I want to combine each raws considering the common values in the first column ex: x 2 7 123 50 3 40 q 5 -9 5 3 5 70 I would be grateful if you could help me with this problem. Thank you. Sapia [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48543 "permalink to this comment") - Philippe Petrinko Jul 29, 2010 @ 11:09 @Sapia: As Vivek may say, “Your post is off-topic. I suggest you use our shell scripting forum for question.” Go <http://nixcraft.com/> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-48547 "permalink to this comment") - borleand Sep 1, 2010 @ 20:23 bash = GPL GPL = GNU GNU = Gnu is Not Unix UNIX logo in your web page = ??? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49160 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Sep 2, 2010 @ 11:45 Does it really matters? Bash runs on both certified UNIX and UNIX like (\*BSD & various Linux distros) operating systems. HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49174 "permalink to this comment") - Philippe Petrinko Sep 2, 2010 @ 12:10 @Vivek Quite right – who cares ? Nobody. I just hope that those guys \[borleand\] would have better working and helping for FOSS community instead of posting those high-quality ( ;-P ) comments. Thanks for such a great web site, Vivek. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49176 "permalink to this comment") - Anthony Thyssen Sep 3, 2010 @ 2:02 Of bigger concern between UNIX, GNU, GPL, Linux, Solaris, MacOSX, or whatever else, is what extra support programs are also available. I use to use ‘seq’ all the time in shell loops. I don’t any more because ‘seq’ is not available on MacOSX. In fact a lot of simple and what I would have though universal support programs are not available on MacOSX. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49188 "permalink to this comment") - naveen Sep 16, 2010 @ 4:53 how do i run 100 iteration using bash shell script.. i want to know how long will it take to execute one command(start and end time). I want to keep track which iteration is currently running. i want to log each iteration. I have one automated script i need to run and log it. for i in 1 2 3 do command1 done But i want to know how long it takes to complete one iteration. and writes a log… help me please [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49549 "permalink to this comment") - Philippe Petrinko Sep 16, 2010 @ 7:15 Hi naveen, 1\) You should at least read thoroughly this topic. Iteration can be done with this syntax Look above for explanation. 2\) You could use \[date\] command and output it to a file – as first command of the iteration (echoing something to mark start) – as last command of the iteration (echoing something to mark end) 3\) Log What kind of log? To know what? What for? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49552 "permalink to this comment") - naveen Sep 16, 2010 @ 15:03 i want to write a output in text file(.txt)(log). I want to have a report saying that test ran for 100 iteration. My question i have one automated script that run 100 test file. i want to know how long it takes to complete the one iteration. And i want to keep a copy of the test result in .txt file. i know this is to log for one iteration……. command \> log.txt But when you are running iteration for 100. How wil you log it??. this is my question. Just one automated script (command) but there will be 100 test results for 100 iteration. How wil you log all this??? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49561 "permalink to this comment") - Philippe Petrinko Sep 16, 2010 @ 15:20 You really seem to be a beginner in shell – the best way to start would be to study Vivek’s Wiki first. Go <http://bash.cyberciti.biz/guide/Main_Page> To answer you iteration question: 1) First write the appropriate \[for\] loop that calls you commands and show us your code. All the information you need is located above in this page. If you cannot write this loop, you’d better learn \[bash\] on Vivek’s Wiki and come back when you can write a \[for\] loop with 100 iteration. Good luck! :) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-49562 "permalink to this comment") - Anthony Thyssen Nov 19, 2010 @ 3:22 The problem with this is that csv files can contain quoted strings. which makes just comma separation usless.. For example LoginN,ssn,ffn “ab1,pp1″,”ab1″,”pp1” “bb1,oo1″,”bb1″,”oo1” “cc1,qq1″,”cc1″,”qq1” [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-50970 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Nov 19, 2010 @ 7:58 In that case use ” as delimiter. This can be done with sed or cut or any other shell built-in or utility: ``` echo '"ab1,pp1","ab1","pp1"' | cut -d '"' -f2 echo '"ab1,pp1","ab1","pp1"' | cut -d '"' -f4 echo '"ab1,pp1","ab1","pp1"' | cut -d '"' -f6 ``` for loop can be used: ``` for i in {2..6..2}; do echo '"ab1,pp1","ab1","pp1"' | cut -d '"' -f${i}; done ``` You can skip for and use sed too. HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-50973 "permalink to this comment") - Anthony Thyssen Nov 22, 2010 @ 1:16 It isn’t quite that simple. But then any CSV that is more complex is getting a bit beyond **simple** shell parsing. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51035 "permalink to this comment") - Anthony Thyssen Nov 22, 2010 @ 1:17 Nifty solution though, especially without access to a multi-character field separator. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51036 "permalink to this comment") - Philippe Petrinko Nov 22, 2010 @ 7:58 Here is another way to do it, – in a generic way, that is without having to know number of internal fields, – without IFS manipulation – without external function (only builtin): Let’s say your CSV file contains 3 fields per record (per line): “aaa bbb ccc”,”ddd eee fff”,”ggg hhh iii”,”jjj kkk lll” “mmm nnn ooo”,”ppp qqq rrr”,”sss ttt uuu”,”vvv www xxx” “yyy zzz 111″,”222 333 444″,”555 666 777″,”888 999 000” To break it in a one-liner, try: The same code in a script is: ``` #!/bin/bash while read do record=${REPLY} echo ${record}|while read -d , do echo ${REPLY} done done<data ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51039 "permalink to this comment") - Philippe Petrinko Nov 22, 2010 @ 8:23 And if you want to get rid of double-quotes, use: one-liner code: ` while read; do record=${REPLY}; echo ${record}|while read -d ","; do field="${REPLY#\"}"; field="${field%\"}"; echo ${field}; done; done<data` script code, added of some text to better see record and field breakdown: Does it work with your data? — PP [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51040 "permalink to this comment") - Philippe Petrinko Nov 22, 2010 @ 9:01 Of course, all the above code was assuming that your CSV file is named “data”. If you want to use anyname with the script, replace: With: And then use your script file (named for instance “myScript”) with standard input redirection: Enjoy\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51041 "permalink to this comment") - Philippe Petrinko Nov 22, 2010 @ 11:28 well no there is a bug, last field of each record is not read – it needs a workout and may be IFS modification ! After all that’s what it was built for… :O) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51043 "permalink to this comment") - Anthony Thyssen Nov 22, 2010 @ 23:31 Another bug is the inner loop is a pipeline, so you can’t assign variables for use later in the script. but you can use ‘\<\<\<' to break the pipeline and avoid the echo. But this does not help when you have commas within the quotes! Which is why you needed quotes in the first place. In any case It is a little off topic. Perhaps a new thread for reading CVS files in shell should be created. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51056 "permalink to this comment") - Philippe Petrinko Nov 24, 2010 @ 18:29 Anthony, Would you try this one-liner script on your CSV file? This one-liner assumes that CSV file named \[data\] has \_\_every\_\_ field double-quoted. Here is the same code, but for a script file, not a one-liner tweak. This script named here \[cvs01.sh\] must be used so: [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51099 "permalink to this comment") - Philippe Petrinko Nov 24, 2010 @ 18:35 @Anthony, By the way, using \[REPLY\] in the outer loop \_and\_ the inner loop is not a bug. As long as you know what you do, this is not problem, you just have to store \[REPLY\] value conveniently, as this script shows. :-P [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-51100 "permalink to this comment") - James Wilkinson Dec 14, 2010 @ 10:03 Thanks for writing this article Vivek – it is very useful. In particular, I didn’t know about bash’s built-in ‘help’ command and was getting frustrated with the lack of detail in ‘man for’ [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-52293 "permalink to this comment") - Sammeta Dec 15, 2010 @ 16:48 Hi i need help in sorting some of the raw data actually on the unix machine. The raw data is some thing like this: ``` TOP;0004796;T0698;3,8;2,2;1,6;19384;1560;28;0;304;12;0;httpd TOP;0004796;T0699;0,2;0,1;0,1;12984;1524;28;0;304;1;0;httpd TOP;0004806;T0145;40,3;38,8;1,5;427904;32648;8;0;1000;62;0;java TOP;0004806;T0146;30,6;29,7;0,8;433152;37684;8;0;1036;29;0;java TOP;0004806;T0147;16,8;16,3;0,6;433808;39152;8;0;1048;11;0;java TOP;0004806;T0148;14,2;13,4;0,7;434132;40300;8;0;1056;11;0;java TOP;0004806;T0149;13,1;12,5;0,6;434196;41644;8;0;1080;7;0;java TOP;0004806;T0150;18,1;17,3;0,8;434276;42556;8;0;1092;18;0;java TOP;0004806;T0151;8,3;7,8;0,5;434316;42624;8;0;1096;1;0;java TOP;0004806;T0152;4,4;4,1;0,4;434328;42916;8;0;1096;9;0;java TOP;0004806;T0153;4,7;4,3;0,4;434352;43204;8;0;1104;9;0;java TOP;0004806;T0154;3,1;2,8;0,3;434404;43260;8;0;1104;1;0;java ... VM;T1439;-1;8;-1;-1;-1;41;0;0;0;7346;0;23;0;2312;2312;0;0;0;0;0;0;0;21;21;0;12;-2633;0;0;0;356;-3;0;0;0;0;0 VM;T1440;-1;6;-1;-1;-1;8893;0;0;0;10808;0;12178;-36;865179;-34821;0;0;8895;0;0;0;0;11758;11758;0;-21;2613;0;0;0;-752;3;0;2;0;0;7 ZZZZ;T0001;00:00:02;18-NOV-2010 ZZZZ;T0002;00:01:02;18-NOV-2010 ZZZZ;T0003;00:02:02;18-NOV-2010 .... ZZZZ;T0140;02:19:04;18-NOV-2010 ZZZZ;T0141;02:20:04;18-NOV-2010 ZZZZ;T0142;02:21:04;18-NOV-2010 ZZZZ;T0143;02:22:04;18-NOV-2010 ZZZZ;T0144;02:23:04;18-NOV-2010 ZZZZ;T0145;02:24:04;18-NOV-2010 ZZZZ;T0146;02:25:04;18-NOV-2010 ZZZZ;T0147;02:26:04;18-NOV-2010 ``` So now it has to check for the time stamp T0145 is the timestamp in the below code : ``` TOP;0004806;T0145;40,3;38,8;1,5;427904;32648;8;0;1000;62;0;java now this has to be mapped with the same time stamp in ZZZZ.......Which is some thing like this from above. ``` ``` ZZZZ;T0145;02:24:04;18-NOV-2010 ``` so finally the output should look like this for every occurance the T value: ``` TOP;0004806;T0145;40,3;38,8;1,5;427904;32648;8;0;1000;62;0;java ZZZZ;T0145;02:24:04;18-NOV-2010, ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-52507 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Dec 15, 2010 @ 18:43 See sort command man page or our sort tutorial related FAQs: [Linux / UNIX Shell: Sort Date](https://www.cyberciti.biz/faq/linux-unix-sort-date-data-using-sortcommand/) [Linux / UNIX Shell: Sort IP Address](https://www.cyberciti.biz/faq/unix-linux-shell-script-sorting-ip-addresses/) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-52518 "permalink to this comment") - Sammeta Dec 16, 2010 @ 15:52 Hi Vivek, Thanks for your reply, but this is just not only sorting but recording on of the value in the above code and then match this with other lines in the code .then display both together. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-52603 "permalink to this comment") - Philippe Petrinko Dec 16, 2010 @ 18:10 @Sammeta, Just trying to help, and not to being rude or anything: We are not willing to do your work, anyone would help people who really try to help themselves first, which you may have been trying already, I suppose. So, would you either submit a first version of your code, or at least a main Algorithm you could think of? You may want to read first \[awk\] or \[join\] unix utilities man pages that you could find anywhere. –P [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-52620 "permalink to this comment") - mohan Jan 5, 2011 @ 0:29 what does FILES=”@” do? Please explain i am new to unix. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-54555 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Jan 5, 2011 @ 7:03 See <http://bash.cyberciti.biz/guide/$@> and <http://bash.cyberciti.biz/guide/Bash_special_parameters> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-54602 "permalink to this comment") - John Jan 5, 2011 @ 1:24 One good reason to use seq instead of the {start..end..increment} idiom: \#! /bin/bash START=1 END=10 INCR=2 echo — use seq — for x in \$(seq \$START \$INCR \$END) do echo \$x done echo — bash idiom — for x in {\$START..\$END..\$INCR} do echo \$x done ———————– — use seq — 1 3 5 7 9 — bash idiom — {1..10..2} [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-54573 "permalink to this comment") - TheBonsai Jan 5, 2011 @ 7:09 Wrong conclusion. This is not a reason for the seq idiom, it’s a reason to use arithmetically driven (C-like) for loops. ``` START=1 END=10 INCR=2 for ((x = START; x <= END; x += INCR)); do echo $x done ``` <http://wiki.bash-hackers.org/syntax/ccmd/c_for> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-54604 "permalink to this comment") - Philippe Petrinko Feb 3, 2011 @ 9:09 @Bonsai: The example you gave is weird regarding shell variable usage: It works, but I thought it should not work\! Within the for (( )) instruction, you omitted “\$” sign to allow variable expansion, but it works! That looks very strange to me. I wrote in an example previously (look above): xstart=1;xend=10;xstep=2 for (( x = \$xstart; x \<= \$xend; x += \$xstep)); do echo \$x;done In your example, you wrote \[for(( ))\] without “\$” : for ((x = START; x \<= END; x += INCR)) I am astonished that for(()) works both with and without “\$” for variable expansion\! xstart=1;xend=10;xstep=2 for (( x = xstart; x \<= xend; x += xstep)); do echo \$x;done Does anyone know why? –PP [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55320 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Feb 3, 2011 @ 12:15 I think it is ksh93 compatibility feature; so “START / END / INCR” will work with no “\$”. See ksh93 man page. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55322 "permalink to this comment") - Philippe Petrinko Feb 3, 2011 @ 13:56 Sorry, I cannot find any evidence of such syntax on khs93 man page – and I use Bash shell. On what URI + what chapter do you think there is an explanation of such behavior? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55327 "permalink to this comment") - TheBonsai Feb 3, 2011 @ 17:01 It’s not KSH (or at least not KSH-unique). It’s how arithmetic environments (of any kind) in Bash work. Also it’s related to what POSIX specifies for the environment inside arithmetic expansion (the only a. environment POSIX knows): > If the shell variable x contains a value that forms a valid integer constant, then the arithmetic expansions “\$((x))” and “\$((\$x))” shall return the same value. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55336 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Feb 3, 2011 @ 17:29 I think it was mentioned in TLDP.org’s advanced bash guide. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55337 "permalink to this comment") - Philippe Petrinko Feb 3, 2011 @ 21:05 Quite right Vivek. <http://tldp.org/LDP/abs/html/arithexp.html> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55343 "permalink to this comment") - toto Feb 16, 2011 @ 5:01 hi, good tutorial. thank you [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-55675 "permalink to this comment") - Víðir Valberg Guðmundsson Mar 8, 2011 @ 3:22 I might be going out on a limb due to a bad case of TL;DR, but I noticed the seq warning. Correct me if I’m wrong but using for instance > for i in \$(seq -w 1 1 20); do echo \$i; done is in my oppinion quite an useful way of using seq in bash, at least when you want leading zeros before 1-9 and not from 10\< Or is there a better way of doing this all "bashy"? ;) \-víðir [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56183 "permalink to this comment") - TheBonsai Mar 8, 2011 @ 6:26 ``` for ((i=1; i<=20; i++)); do printf "%02d\n" "$i"; done ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56186 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Mar 8, 2011 @ 6:37 \+1 for printf due to portability, but you can use bashy .. syntax too ``` for i in {01..20}; do echo "$i"; done ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56187 "permalink to this comment") - TheBonsai Mar 8, 2011 @ 6:48 Well, it isn’t portable per se, it makes it portable to pre-4 Bash versions. I think a more or less “portable” (in terms of POSIX, at least) code would be ``` i=0 while [ "$((i >= 20))" -eq 0 ]; do printf "%02d\n" "$i" i=$((i+1)) done ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56188 "permalink to this comment") - ankit gulati Mar 12, 2011 @ 14:44 Hi Can anybody help for this. I have two text file viz gem1.txt and gem2.txt EX. Content of gem1.txt activerecord (2.3.5, 2.2.2) activerecord-oracle\_enhanced-adapter (1.1.9) activerecord-sqlserver-adapter (2.3.4) activeresource (2.3.5, 2.2.2) Now i have to put all the data of these two .txt file on gem.csv. column wise. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56293 "permalink to this comment") - Philippe Petrinko Mar 12, 2011 @ 22:58 @ankit gulati This is not a place :-P for such questions, go and see Forum. <http://nixcraft.com/> Anyway an answer is \[paste\] command. :-) <http://linux.die.net/man/1/paste> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56298 "permalink to this comment") - PiCarre Mar 20, 2012 @ 9:15 Simply use the “paste” command. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-68468 "permalink to this comment") - Rupender Mar 23, 2011 @ 15:48 Hi can some one help in ceating a loop the problem is i have 3 folder and name of the folder changes. i want a loop which enter these folder one by one echo the files inside the folder [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56597 "permalink to this comment") - Philippe Petrinko Mar 23, 2011 @ 19:27 Hi following this topic, you may try to write something down first, and then we may help you … if you help yourself first. Read and use this topic, and the following material: <http://bash.cyberciti.biz/guide/Main_Page> However, such request would be best posted into the forum <http://nixcraft.com/> Anyway, a simple solution would be to use \[ls\] command with appropriate arguments. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-56611 "permalink to this comment") - Philip Ratzsch Apr 20, 2011 @ 5:53 I didn’t see this in the article or any of the comments so I thought I’d share. While this is a contrived example, I find that nesting two groups can help squeeze a two-liner (once for each range) into a one-liner: for num in {{1..10},{15..20}};do echo \$num;done Great reference article\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-57422 "permalink to this comment") - Philippe Petrinko Apr 20, 2011 @ 8:23 @Philip Nice thing to think of, using brace nesting, thanks for sharing. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-57427 "permalink to this comment") - David May 4, 2011 @ 10:10 Hi guys. I was wondering whether it is possible to run a for loop through rsh (now before you start protesting that I use rsh instead of ssh; I know that it is extremely insecure. Thanks.) like this:? rsh -l dev 192.168.x.x “for file in /PackSun/distills/\*; do if \[\[ \${file} =~ “3\\.6\\.76″ \]\]; echo \$file; fi; done” Because when I type this it doesn’t work, \$file is always the same file and it comes from the pwd on the local machine, not on the remote. Thanks in advance. D [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59181 "permalink to this comment") - David May 4, 2011 @ 10:11 damn, sorry, didn’t close the code tag: rsh -l dev 192.168.x.x “for file in /PackSun/distills/\*; do if \[\[ \${file} =~ “3\\.6\\.76” \]\]; echo \$file; fi; done” [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59182 "permalink to this comment") - Anthony Thyssen May 5, 2011 @ 2:57 First — you should not use rsh. It is an old and insecure network protocol. ssh is its replacement. As for your question YES it is posible, Wrap it in a ‘shell’ command. rsh -l dev 192.168.x.x ‘sh -c ‘\\”for file in /PackSun/distills/\*; do if \[\[ \${file} =~ “3\\.6\\.76″ \]\]; echo \$file; fi; done’\\’ Watch the quoting as you want to use single quotes for both the outside and inside commands. If you use ” quotes you will need to escape the \$ characters instead! And that may in turn lead to escapes of escapes (not pretty). I have actually done this to execute a very very large shell script on a remote server. However I don’t recommend it for things beyond what you have. If need be copy (update) a shell script on the remote server (scp, rsync, etc) then execute that. It works better, you do not have constant quote handling problems, and not command line length limits. I do this for a [incremental home backup program]() (written for my own use, using rsync hardlinks backup directories), that can backup to a remote account. You are free to download and look at the copy/execute remote script that the main script performs for its sub-scripts (like backup cycle rolls). [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59207 "permalink to this comment") - Philippe Petrinko May 5, 2011 @ 13:10 Anthony, You forgot to include URI for you script, your \> a \< tag is empty. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59225 "permalink to this comment") - Anthony Thyssen May 5, 2011 @ 3:01 PS: the reason for the ‘sh -c …’ is beause you may nto have control of the login shell of the remote account. If you did not have it and the remote accoutn used tcsh or zsh, you will have problems. PPS; you are missing a then. I tested it with this ssh version (a shell-builtin only ‘ls’ of the remote account). ssh remote\_machine ‘sh -c ‘\\”for file in \*; do echo \$file; done’\\’ [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59208 "permalink to this comment") - Sanya May 6, 2011 @ 6:02 Hello I am using bash V4+ and this loop works fine: for i in {1..10}; do echo \$i; done But when I put variables in the loop max=10; for i in {1..\$max}; do echo \$i; done I see one line as output: {1..10} Could anybody explain me what’s wrong ? Cheers. Sanya [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59243 "permalink to this comment") - Philippe Petrinko May 6, 2011 @ 10:13 Hello Sanya, That would be because brace expansion does not support variables. I have to check this. Anyway, Keep It Short and Simple: (KISS) here is a simple solution I already gave above: xstart=1;xend=10;xstep=1 for (( x = \$xstart; x \<= \$xend; x += \$xstep)); do echo \$x;done Actually, POSIX compliance allows to forget \$ in for quotes, as said before, you could also write: xstart=1;xend=10;xstep=1 for (( x = xstart; x \<= xend; x += xstep)); do echo \$x;done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59249 "permalink to this comment") - Philippe Petrinko May 6, 2011 @ 10:48 Sanya, Actually brace expansion happens \_\_before\_\_ \$ parameter exapansion, so you cannot use it this way. Nevertheless, you could overcome this this way: max=10; for i in \$(eval echo {1..\$max}); do echo \$i; done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59251 "permalink to this comment") - Sanya May 6, 2011 @ 11:42 Hello, Philippe Thanks for your suggestions You basically confirmed my findings, that bash constructions are not as simple as zsh ones. But since I don’t care about POSIX compliance, and want to keep my scripts “readable” for less experienced people, I would prefer to stick to zsh where my simple for-loop works Cheers, Sanya [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59252 "permalink to this comment") - Philippe Petrinko May 6, 2011 @ 12:07 Sanya, First, you got it wrong: solutions I gave are not related to POSIX, I just pointed out that POSIX allows not to use \$ in for (( )), which is just a little bit more readable – sort of. Second, why do you see this less readable than your \[zsh\] \[for loop\]? for (( x = start; x \<= end; x += step)) do echo "Loop number \${x}" done It is clear that it is a loop, loop increments and limits are clear. IMNSHO, if anyone cannot read this right, he should not be allowed to code. :-D BFN [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59254 "permalink to this comment") - Anthony Thyssen May 8, 2011 @ 23:30 If you are going to do… \$(eval echo {1..\$max}); You may as well use “seq” or one of the many other forms. See all the other comments on doing for loops. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59312 "permalink to this comment") - Tom P May 19, 2011 @ 12:16 I am trying to use the variable I set in the for line on to set another variable with a different extension. Couldn’t get this to work and couldnt find it anywhere on the web… Can someone help. Example: ``` FILE_TOKEN=`cat /tmp/All_Tokens.txt` for token in $FILE_TOKEN do A1_$token=`grep $A1_token /file/path/file.txt | cut -d ":" -f2` ``` my goal is to take the values from the ALL Tokens file and set a new variable with A1\_ infront of it… This tells be that A1\_ is not a command… *Edited by admin: Added pre taga* [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59511 "permalink to this comment") - atef fawzy May 23, 2011 @ 10:27 could you please help me in write a bash script do the following: 1- read an input file contains IP Port 2- check the connectivity for every IP and its Port via telnet 3- if the telnet not connected send email to alert me. thanks in advance atef fawzy [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59572 "permalink to this comment") - Philippe Petrinko May 23, 2011 @ 11:34 No problem. Would you first send me 1000USD payment? Thanks in advance. ;-) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59576 "permalink to this comment") - atef fawzy May 23, 2011 @ 12:37 dear Philippe Petrinko thank you a lot for you value site the below is my script and i don’t know what is the wrong?can you help me \#!/bin/sh for ip in \$(cat iplist); do \# check for open ports \# connTest=\`echo ” ” \| telnet \$ip\` if \[ “\`echo \$ip \| awk ‘{ print \$3 }\` = “Connected” \] then echo “\$ip is up” else \#echo “\$connTest port is down” echo \$ip is down fi done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59580 "permalink to this comment") - Philippe Petrinko May 23, 2011 @ 12:25 Lucky You! Atef fawzy, Vivek has already written necessary training material for you: Read <http://bash.cyberciti.biz/guide/Main_Page> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59578 "permalink to this comment") - atef fawzy May 23, 2011 @ 12:41 please tell me what is the wrong? \#!/bin/sh for ip in \$(cat iplist); do \# check for open ports \# connTest=\`echo ” ” \| telnet \$ip\` if \[ “\`echo \$ip \| awk ‘{ print \$3 }\` = “Connected” \] then echo “\$ip is up” else echo \$ip is down fi done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59581 "permalink to this comment") - atef fawzy May 23, 2011 @ 12:33 dear Philippe Petrinko thank you a lot for your value site the below is my script and i don’t know what is the wrong? can you hep me please \#!/bin/sh for ip in \$(cat iplist); do \# check for open ports \# connTest=\`echo ” ” \| telnet \$ip\` \#if \[ “\`echo \$connTest \| awk ‘{ print \$3 }\` ” = “Connected” \] if \[ “\`echo \$ip \| awk ‘{ print \$3 }\` = “Connected” \] then \#echo “\$connTest port is up” echo “\$ip is up” else \#echo “\$connTest port is down” echo “\$ip is down” fi done [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59579 "permalink to this comment") - Philippe Petrinko May 23, 2011 @ 13:39 Your request is off-topic. Your \[for\] loop works fine, so this is not a point to be discussed here, Your \[if\] test is buggy – not to be discussed here but there <http://nixcraft.com/> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59582 "permalink to this comment") - atef fawzy May 24, 2011 @ 10:20 please send me the full URL to post the error i got [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59598 "permalink to this comment") - Philippe Petrinko May 24, 2011 @ 11:14 You can go where I already offered you =\> <http://nixcraft.com/> You can go there and figure out what topic is appropriate to your needs. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59599 "permalink to this comment") - loop how May 26, 2011 @ 0:49 \#!/bin/sh How can I do this using infinite loops? ``` for disk in $(ls /dev/disk/by-id/ | grep -v part | grep scsi-35000I); do echo $disk && \ dd if=/dev/zero of=/dev/disk/by-id/$disk bs=8M oflag=direct count=250 && \ dd if=/dev/disk/by-id/$disk of=/dev/null bs=8M count=250; done ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-59626 "permalink to this comment") - Chu-Siang Jul 21, 2011 @ 21:07 thanks for you example, It\`s help me very much. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-60922 "permalink to this comment") - Faizanul Islam Jul 26, 2011 @ 6:04 hey, Thanks a lot. Example are in the way they should be…some of the examples are very new to me. It has increased by knowledge. keep posting these things and let us increase our knowledge. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61007 "permalink to this comment") - brian Aug 5, 2011 @ 7:58 Hi, I have to read a file line by line and do the iteration and apply the condition parameter for each input . Please share your ideas [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61315 "permalink to this comment") - Philippe Petrinko Aug 5, 2011 @ 9:56 @Brian You could google “awk” to proceed a file line by line, of use example in Vivek’s blog. <http://bash.cyberciti.biz/file-management/read-a-file-line-by-line/> <https://www.cyberciti.biz/faq/unix-howto-read-line-by-line-from-file/> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61322 "permalink to this comment") - Sam McAllister Aug 10, 2011 @ 11:10 Hi, I’m a beginner and I was writing a very simple script : \#!/bin/sh clear echo “Enter username:” read username if \[ “\$username” = “newbay” \] then echo “Username correct,” else echo “Incorrect username, try again:” fi echo “Now enter password:” read password if \[ “\$password” = “welcome” \] then echo “You are now logged in.” else echo “Sorry, incorrect password. Please try again.” fi and I was wondering how to loop the incorrect username try again part ? Can anyone help me, if they understand my awful script .. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61450 "permalink to this comment") - Anthony Thyssen Aug 11, 2011 @ 7:25 Start a new thread\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61470 "permalink to this comment") - Sam McAllister Aug 11, 2011 @ 7:47 Haha ok thanks :) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61471 "permalink to this comment") - Philippe Petrinko Aug 11, 2011 @ 8:48 You could start learning shell scripting: About \[for\] loops: <http://bash.cyberciti.biz/guide/For_loop> ( from that excellent <http://bash.cyberciti.biz/guide/Main_Page> ) Enjoy\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61474 "permalink to this comment") - ITtuition.com Aug 11, 2011 @ 13:30 Spot on. Included all examples that form a good base. Thanks for sharing. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-61483 "permalink to this comment") - Nagesh Sep 14, 2011 @ 10:21 This post is 3 yrs old but still RockS.\\m/ [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-62416 "permalink to this comment") - ptrac3 Oct 24, 2011 @ 17:43 Very handful tutorial! : ) But i’ve got a problem on my Ubuntu linux box, a strange problem.. Executing the example code \#!/bin/bash for i in {1..5} do echo “Welcome \$i times” done i get as output Welcome {1..5} times. So the bash doesn’t understand the range {1..5}…Have any idea? My bash version is GNU bash, version 4.2.8(1)-release (x86\_64-pc-linux-gnu). Thank u : ) [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-63856 "permalink to this comment") - Philippe Petrinko Oct 25, 2011 @ 9:01 This code has to be written into a text file, which must be made executable. Did you do that? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-63869 "permalink to this comment") - 👮🛡️  [nixCraft](https://www.vivekgite.com/) Oct 25, 2011 @ 11:19 GNU/Bash v4.2.8 does supports {1..5} syntax. What is the output of the following commands? ``` ls -l /bin/bash /bin/bash --version ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-63871 "permalink to this comment") - Sonia McMath Nov 18, 2011 @ 6:52 Great weblog right here! Additionally your web site quite a bit up very fast! What host are you the usage of? Can I get your associate hyperlink for your host? I want my website loaded up as fast as yours lol [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-64564 "permalink to this comment") - Hannah Dec 5, 2011 @ 23:21 Hi all… I have a question about using for loops. Basically, I have a file containing a list of protein ID numbers. what I want to do is create a for loop that can go into this file, grab each protein ID number, and then search the NCBI database to get the fasta sequence of each protein… and then create another file containing all of the fasta sequences…. In general, my problem is that I can’t figure out how to get the protein ID numbers from the output file (ex. \$1 in file1) into the for loop script. This is what I have so far: for gi in file1 do fastacmd -d /data/nr -s gi done but I need to specify that the gi (protein ID number) is the first column (\$1) of file1. Does this make sense? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-65210 "permalink to this comment") - Akshit Dec 7, 2011 @ 12:36 Hi… Thanks for the article, it is helpful really. I want to know one thing. Let’s say there is file with content 1 2 3 4 5 how can I use for loop and print these numbers? If you are understanding what I am trying to tell. I want to use the contents of these files and stored in the variable. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-65270 "permalink to this comment") - andreea Jan 5, 2012 @ 16:21 Hello\! i am beginner and i have to make a bash script in which i have to show the number of lines that were added by the analized commits(in git).can you help me?Thanks. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66417 "permalink to this comment") - Philippe Petrinko Jan 5, 2012 @ 17:33 Dear andreea 1\) I quote Vivek: “You are free to use our shell scripting forum for questions.” <http://nixcraft.com/shell-scripting/> 2\) You can learn for free shell scripting with the infamous Vivek’s collaborative Linux Shell Scripting Tutorial <http://bash.cyberciti.biz/guide/Main_Page> Enjoy\! — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66418 "permalink to this comment") - Philippe Petrinko Jan 5, 2012 @ 18:23 “infamous” was a private joke-understatement Sorry, no offense intended\! Vivek website roxxxxs \! — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66420 "permalink to this comment") - andreea Jan 6, 2012 @ 18:33 Thanks for your quick answer. I have another problem.i have to use this script by using git.can you explain me or give some advices how can i use it?thank you very much. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66467 "permalink to this comment") - andreea Jan 8, 2012 @ 20:54 I have this code that shows the first column which represents the number of insertions of a commit and calculate the sum of all numbers of each line. if \[ \$\# -eq 2 \]; then if \[ \$2 = “added\_lines” \]; then tmpfile=\$(mktemp) sum=0 git log –pretty=tformat: –numstat \| tr -s “\\n” \| cut -f 1 \> \$tmpfile for i in \$(cat \$tmpfile); do sum=\$((\$sum + \$i)) done echo “\$sum” rm \$tmpfile But with ‘cut -f 1’ it takes too much time to calculate and to show the result.Can you help me saying how can i do this with ‘awk’ or ‘gawk’? Please help me.Thanks [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66511 "permalink to this comment") - Ram Jan 10, 2012 @ 18:57 Hi Vivek, i am trying to run the below code as ram.sh in server as \$ sh ./ram.sh code: ————————- \#!/bin/bash for i in 1 2 4 do echo “Welcome \$i times” done ————————- It fails saying ram.sh: line 3: syntax error near unexpected token \`do ram.sh: line 3: \`do is that something i need to check which version is the sh and bash used in the server. how to check that. it is a pretty simple code and it is not workign. i am running this script in Linux server 64 bit server. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-66611 "permalink to this comment") - the dsc Oct 23, 2012 @ 2:54 What’s the easiest way to have a loop from N to N, when the numbers are dictated by variables? Something like what one could/would expect from “for i in {\$a..\$b}”, but something that actually works of course. What I do is: a=0 ; b=5 ; until ((a==b)) ; do echo \$a ; a=\$((\$a+1)) ; done But it seems kind of dumb, somewhat like echoing a huge set of spaces instead of “clear”, to clear the screen. But perhaps it’s the only way to do it. And it works anyway, so perhaps it’s good enough and worthy as an addition rather than a question. Funnily enough you can make an alphabetic countdown with “for i in {a..z}” [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-72456 "permalink to this comment") - Philippe Petrinko Jan 27, 2012 @ 10:07 Hi Ram, Since you are a real beginner, you would really take great benefit self-training on this course free of charge by vivek & contributors: <http://bash.cyberciti.biz/guide/Main_Page> –P [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-67620 "permalink to this comment") - shahzad Mar 10, 2012 @ 9:04 Hi, I have this code in NetBeens: \#include \#include using namespace std; int main() { int a,i,j; cout \<\< "inter your number of row " \<\>a; for (i=0; i\<=a; i++) { for(j=0; j\<=i; j++) { cout \<\< "\*"; } cout \<\< '\\n'; } return 0; } but I want to run it in ubuntu so at first I made a " nano file.sh" aftaer that I wrote this code in it: \#!/bin/sh echo “Enter your number of rows” Read a for((i=0; i\<=a; i++)) do for((j=0; j\<=i; j++)) do echo “\*” done echo –n done exit 0 after that " chmod +x file.sh", but my code didn't run, my code in ubuntu has problem, I don't know how can I solve it, Thanks a lot if you answer my question, Regards [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-68323 "permalink to this comment") - regan May 5, 2012 @ 14:26 hi, am having problem to write a program using For statement. Please help if you know something about using For statement [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-69226 "permalink to this comment") - Excellent\_Test Aug 23, 2012 @ 11:57 This is what I was looking for. TLDP advanced guide is also good one. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-71117 "permalink to this comment") - Philippe Petrinko Nov 12, 2012 @ 19:38 Vivek, It seems that Wordpress was hungry, it has eaten your text ;-) \[for\] code sample is broken after sentence: “A representative three-expression example in bash as follows” –P [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-73198 "permalink to this comment") - Youshi Patel Feb 20, 2013 @ 15:14 nice write up. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-79795 "permalink to this comment") - m.vinothini Mar 7, 2013 @ 6:17 very useful [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-81499 "permalink to this comment") - OSuKaRu Jun 6, 2013 @ 20:54 i try the infinite variable, but it tells me that: Syntax error: Bad for loop variable :\< [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-93592 "permalink to this comment") - K J Ramana Rao Jun 20, 2013 @ 14:26 Hello, Nice post. Please help me in below code. we are getting syntax error. Please resolve the syntax issue. ``` if [ $1 ] ; then LIB=$1/lib if -d ${_LIB} ; then for jar in (cd ${_LIB}; ls *.jar) do EXISTS=echo ${CP} | grep "/${jar}" if [ "${_EXISTS}" != "" ]; then logger "WARN: Classpath will contain multiple files named ${jar}" else CP=${CP}${CP_DELIM}${LIB}/${jar} fi done fi cd $1 fi } ``` Error: ``` syntax error near unexpected token `(' line 15: `for jar in (cd ${_LIB}; ls *.jar)' ``` Thanks Ramana [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-94809 "permalink to this comment") - Anthony Thyssen Jun 24, 2013 @ 0:43 You are a ‘help troll’.. You posted in the wrong section. you would have been better of starting a new topic. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-95113 "permalink to this comment") - foolar Jun 21, 2013 @ 13:20 try with if \[ \$1 \] ; then LIB=\${1}/lib if -d \${\_LIB} ; then for jar in \$(cd \${\_LIB}; ls \*.jar) do EXISTS=\$(echo \${CP} \| grep “/\${jar}”) if \[ “\${\_EXISTS}” != “” \]; then logger “WARN: Classpath will contain multiple files named \${jar}” else CP=\${CP}\${CP\_DELIM}\${LIB}/\${jar} fi done fi cd \$1 fi [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-94923 "permalink to this comment") - abr Jun 27, 2013 @ 0:51 hi if I use it with a imput variable like: echo “enter the numbers of repetitions :” read variable tthe variable represent the number example 15 times to repeat !!!???/ how could it be ??? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-95288 "permalink to this comment") - dennis bernaerts Jul 4, 2013 @ 13:19 nice and clear thx a lot. What I am dreaming of is this clear kind of webpage in which each box has a tab in which you can select any language…. I’m sure it exists already but where ??? and I mean it needs to be clear and simple !\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-95767 "permalink to this comment") - Tring Tring Sep 24, 2013 @ 9:27 Thank you so Much\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-98836 "permalink to this comment") - sana Oct 2, 2013 @ 10:40 hi i have a problem i want to write a shell script for siesta. i want to make diffrent directories and want to change lattice constants n then run it with siesta n want to chck total energy cn u tell m how cn i do this [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99007 "permalink to this comment") - Philippe Petrinko Oct 2, 2013 @ 12:32 no w cnt sry w dnt 1drstnd w U sd [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99008 "permalink to this comment") - sana Oct 3, 2013 @ 6:26 I want to write a shell script for diffrent values of lattice constants . If i do manually i first make a directorie i.e for 3.80 then i copy \*.psf and fdf file there open the fdf file and change lattice constant to 3.80 and the execute file with siesta and note the total energy. n again i repeat the same process for let say 3.90,4.10.4.20 etc. now i want to write a code in shell so that i dnt need to make directory every time and change lattice constant. I want to use looping for this purpose……..but how?? anybody have the little code for this?or anything? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99023 "permalink to this comment") - sana Oct 3, 2013 @ 6:31 \#!/bin/bash \# changing lattice constants for 3.80 3.90 in \$inp3.70.fdf do echo 3.80 3.90 mkdir mv inp3.70.fdf inp\*.fdf.old mv \*.psf \*.psf.old sed ‘s/inp\*.fdf/&, lattice constant/’ inp\*.fdf done \# Now comes the commands to be executed ~/code/sanabin/siesta 3.70.out & ~ as i write this but not working…….. ../ [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99024 "permalink to this comment") - Philippe Petrinko Oct 3, 2013 @ 7:48 Well, it seems that you do not understand the basics of shell scripting, even a simple \[mkdir\] command. Anyway, you are very lucky, because this web site and Internet offer you \_free\_ training material. The good news is : all you have to do is learn and work, using for instance these links. <http://bash.cyberciti.biz/guide/Main_Page> <http://bash.cyberciti.biz/script/for-loop/> and of course this page <https://www.cyberciti.biz/faq/bash-for-loop/> [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99026 "permalink to this comment") - matthias Oct 10, 2013 @ 5:19 nice you used “c++” in “A representative three-expression example in bash” but that is a programing language. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99173 "permalink to this comment") - Philippe Petrinko Oct 10, 2013 @ 9:18 @matthias : What’s your point? Is it a humorous play of words on “C++” language and increment of c variable in this script? In that case it would have been more convenient to append a smiling smiley, because otherwise, there is no coding issue in “A representative three-expression example in bash”. :-/ wondering… — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-99176 "permalink to this comment") - ravindra Dec 3, 2013 @ 15:00 Hi.. check it ``` for (( c=1; c<=5; c++ )) do echo "Welcome $c times" done ``` why came this error in ubuntu please tell me reply please ./for3: 1: ./for3: Syntax error: Bad for loop variable [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-107366 "permalink to this comment") - Vamsi Dec 1, 2014 @ 11:18 Hi, It works for BASH only. Check you have given the right interpretor at the top of the script. You can give it by placing \#! /bin/bash at the top. –Vamsi [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-432960 "permalink to this comment") - RH User Jan 3, 2014 @ 21:12 Thanks. Solved my coding issue. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-111773 "permalink to this comment") - dee Jan 17, 2014 @ 20:27 Can anyone advise how to write a for loop statement to run commands from a .sh when an event comes up like users uploading new files to the server. My issue is that I am using a soft link to mirror an external disk drive in the .www/ and the soft link never updates when a new content is added to the drive within a session. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-112630 "permalink to this comment") - Dai Jun 18, 2014 @ 14:16 Hi. Nice overview of for loops. I have a question, however: Using the old “seq” command, one could perform zero padding via “seq -f “%05g” 1 100″. How would this work with the {1..100} (or other) syntax? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-212077 "permalink to this comment") - Philippe Petrinko Jun 19, 2014 @ 7:00 Hi Dai, simple: 1\) for x in {0001..10} ; do echo “padding :\$x:”; done 2\) Actually it works specifying padding on first argument (here 0001). No need to specify padding on second argument, but it will either work. for x in {0001..0010} ; do echo “padding :\$x:”; done 3\) but beware: you can specify different padding on both arguments, but only the \_longuest\_ will be used \! so this will use 6 digits padding, not 3 \! for x in {001..000010} ; do echo “padding :\$x:”; done ok ? Vivek, would improve this topic on for loop adding this information on padding? It seems to be useful and at least informative and relevant to this topic. — Philippe [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-212364 "permalink to this comment") - Dai Jun 19, 2014 @ 7:33 Marvelous. Cheers\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-212390 "permalink to this comment") - dronkit Apr 1, 2015 @ 20:55 You cannot completely abandon seq for the new bash syntax. Apparently, all variables in bash are integers. I tried using the new syntax with negative and float numbers with disastrous results. Seq, in turn, does it wonderfully. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-629365 "permalink to this comment") - Johnny Rosenberg Aug 6, 2015 @ 15:07 Ooops, forget it, someone else said the same thing. Didn’t see that, I’m not sure why… [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-725348 "permalink to this comment") - wt Sep 24, 2015 @ 13:06 1 line loop, for example curling: for i in {1..500}; do curl “https://localhost:8040”; done; [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-748141 "permalink to this comment") - onews Nov 3, 2015 @ 14:05 How do we do something like: for file in /etc/\* /bin/\* [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-757486 "permalink to this comment") - Carlos Luna Nov 14, 2015 @ 3:32 Useful information! thank you\! Can somebody explain me what this loop “for i in circles\[0,:\]:” means? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-759473 "permalink to this comment") - Sasha Dec 22, 2015 @ 14:41 HI: I use seq when I need variables in the loop limits, because as far as I remember for y in {\$x1..\$x2}… is not allowed. Cheers [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-768649 "permalink to this comment") - nezabudka Jan 3, 2016 @ 16:39 Sasha [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-772079 "permalink to this comment") - Emma Edwards Mar 18, 2016 @ 14:22 Hi i would like to know how to loop numbers using terminal but i tant seem to find how to so it would be gréât if one of you can help me [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-802421 "permalink to this comment") - Emma Edwards Mar 18, 2016 @ 14:23 sorry i ment i cant seem to find…. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-802424 "permalink to this comment") - Golla praveen Jun 14, 2016 @ 13:59 \#!/bin/bash for ((i=1;i\<=100;i++)); do echo \$i while excute the above program the below errors comes please check revert [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-866375 "permalink to this comment") - mito Jul 1, 2016 @ 8:42 hi i would like to know how i write a shell script to search a 100 user home directory by certain file can you help me? thx [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-882562 "permalink to this comment") - mito Jul 1, 2016 @ 8:45 output is username und the file [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-882563 "permalink to this comment") - Chad Nov 23, 2016 @ 15:41 Hey I hope you can help me here. I’m stuck. down vote favorite Trying to bind 20 x /24 subnets in Ubuntu 14 Server but I’m stuck here. These are diversified /24 subnets. I tried the below method via script called addips.sh for i in \$(seq 3 254); do echo “auto em1:\$i iface em1:\$i inet static address xxx.xxx.16.\$i netmask 255.255.255.0 ” \>\> virthosts; done But, I noticed that this happened now: Each /24 subnet it outputted started off at \#1 again instead of 255, 256, 257, etc all the way through consecutively for all 20 x /24 subnets auto em1:1 auto em1:254 Then again… auto em1:1 … How can I properly change this so it does reset at \#1? em1 is the NIC Ethernet port (primary) and only port used too. I also want to make sure these are permanent, they stick after a server reboot. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-910774 "permalink to this comment") - Jignesh Dec 19, 2016 @ 7:36 Hello There, I want to make one scipt which shall change multiple file name as per below example 1\) if file name contains \*abc\* then file name should be change to \*xyz\* 2) if file name contains \*def\* then file name should be change to \*iop\* 3) if file name contains \*(any file name except above name) then file name should be change to \*qwe\* Kindly help me to make the script as mentioned above requirement Thanks!\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-910907 "permalink to this comment") - urvashi Feb 3, 2017 @ 12:58 Very useful.Simple and easy. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-911190 "permalink to this comment") - Alex Mar 16, 2017 @ 20:32 These are great examples, although I am hoping someone can help me with an easy one. Below is a simple script, but I would like for it to ask for another hash or give the option to break instead of just breaking. ``` #!/bin/sh URL=server.domain.com TOKEN=A8B6389DEBA9FE3DA88DF2E785E4C echo "Hello, my name is" $TOKEN echo -n "Now, enter a hash: " read HASH curl -H "X-TOKEN-KEY: $TOKEN" https://$URL/hashcheck/check?hash=$HASH ``` [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-911427 "permalink to this comment") - Danny May 23, 2017 @ 21:40 I would like to know how can i use for loop to pick up first few files from directory do something and then run with next batch. Currently, I am able to for each file it takes one file at a time however i want to launch a command against 4 files at a time and then move on to next set in same directory. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-920328 "permalink to this comment") - no Aug 31, 2017 @ 17:29 Arrays start at 0. Kill yourself [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-920695 "permalink to this comment") - Sundaram Sep 24, 2020 @ 14:32 This helped. Thank you\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-932567 "permalink to this comment") - Jon Seidel Oct 1, 2020 @ 13:25 The array syntax in the For loop with array example (<https://www.cyberciti.biz/faq/bash-for-loop/#For_loop_with_array_elements>) is incorrect — there are no commas required in the list; arrays should be coded as follows: `MY_ARRAY=('one' 'two' 'three') # space-separated` The arrays in the example are tacked on to the end of the previous string. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-932607 "permalink to this comment") - 👮🛡️  [Vivek Gite](https://www.vivekgite.com/) Oct 1, 2020 @ 16:23 Thanks for the heads up. The page has been updated. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-932608 "permalink to this comment") - David W Thomson Nov 26, 2020 @ 3:55 How can we loop through a directory structure such as /2010/11/25/0.sac; where 0.sac is a range of files from 0 to 23? I have three years of earthquake data to run an FFT analysis on. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-932932 "permalink to this comment") - 👮🛡️  [Vivek Gite](https://www.vivekgite.com/) Nov 26, 2020 @ 8:40 Try range feature as follows: ``` for f in /2010/11/25/{0..23}.sac do # $f is your filename now echo "Working on $f file now ..." done ``` HTH [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-932934 "permalink to this comment") - thomas Jan 26, 2021 @ 8:16 Seems helpful but my case I didn’t find. Regards [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-933334 "permalink to this comment") - Salvimani Jun 5, 2021 @ 4:19 Useful examples and contents for us. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-934990 "permalink to this comment") - Ahamed Kabeer KS Apr 10, 2022 @ 10:28 Thanks [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-942262 "permalink to this comment") - tre\*\*\*\*\*@gmail com May 16, 2022 @ 11:16 This was totally helpful. Thanks a bunch. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-942502 "permalink to this comment") - Brad Jun 27, 2022 @ 8:31 I would suggest adding: ``` for g in smith{3..1..-1}; do echo "${g}" done ``` to show how to loop in a descending range. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-942714 "permalink to this comment") - Dragan Oct 21, 2022 @ 6:34 Thanks, very helpful\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-943460 "permalink to this comment") - d Jan 23, 2023 @ 10:23 In the example “For loop with array elements” there’s a typo, no? You would need to escape the newline after the line that says: –availability-zone “\$zone” or am I mistaken? [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-944169 "permalink to this comment") - 👮🛡️  [Vivek Gite](https://www.vivekgite.com/) Jan 23, 2023 @ 17:38 Yes, you need to escape the newline. I fixed it. Thanks for the heads up\! [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-944175 "permalink to this comment") - RAJU Feb 7, 2023 @ 9:54 How to create file dependency in shell scripting. we have to use if else condition in shell script and create a while loop or for loop and make iteration. in the first iteration check all the files are coming or not. Then After completion for one iteration wite for 10 seconds. Then second iteration we have to give the count all files are coming or not. if all the files are received then coming out off the while loop. if all files are not coming in one hour, then we can create email. [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-944271 "permalink to this comment") - alam Feb 20, 2023 @ 14:55 I have a .bat script, which reads two kinds of files of the same name and different extensions, given below; ./example.data. \#.data file in the current directory ./example.fstat. \#.fstat file in the current directory 0010 0020 1 \#read the 5 files from example.data.00500 and example.fstat.00500 \\mv tav12.data tav12\_\$NC\\\_IS\$IS\\\_YADEII\_0300\_tav12\_10\_20.data I want to use a for loop to produce output from file range 0010 to 0050 by reading each five pair of .data and .fstat files and produce output with different name. I will be highly grateful, thanks in advance [∞](https://www.cyberciti.biz/faq/bash-for-loop/#comment-944350 "permalink to this comment") Comments are closed. Still have questions? [Post it on our forum](https://www.nixcraft.com/) Next FAQ: [How to edit a file when you are viewing it using more / less pager](https://www.cyberciti.biz/faq/edit-file-when-youre-viewing-withmore-less/) Previous FAQ: [Upgrade Ubuntu Hardy Heron Server 8.04 To Ubuntu Server 8.10 Intrepid Ibex](https://www.cyberciti.biz/faq/howto-upgrade-ubuntu-servers-804-to-810/) 🔥 FEATURED ARTICLES - 1 [30 Cool Open Source Software I Discovered in 2013](https://www.cyberciti.biz/open-source/30-cool-best-open-source-softwares-of-2013/) - 2 [30 Handy Bash Shell Aliases For Linux / Unix / Mac OS X](https://www.cyberciti.biz/tips/bash-aliases-mac-centos-linux-unix.html) - 3 [Top 32 Nmap Command Examples For Linux Sys/Network Admins](https://www.cyberciti.biz/networking/nmap-command-examples-tutorials/) - 4 [25 PHP Security Best Practices For Linux Sys Admins](https://www.cyberciti.biz/tips/php-security-best-practices-tutorial.html) - 5 [30 Linux System Monitoring Tools Every SysAdmin Should Know](https://www.cyberciti.biz/tips/top-linux-monitoring-tools.html) - 6 [40 Linux Server Hardening Security Tips](https://www.cyberciti.biz/tips/linux-security.html) - 7 [Linux: 25 Iptables Netfilter Firewall Examples For New SysAdmins](https://www.cyberciti.biz/tips/linux-iptables-examples.html) - 8 [Top 20 OpenSSH Server Best Security Practices](https://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html) - 9 [Top 25 Nginx Web Server Best Security Practices](https://www.cyberciti.biz/tips/linux-unix-bsd-nginx-webserver-security.html) - 10 [My 10 UNIX Command Line Mistakes](https://www.cyberciti.biz/tips/my-10-unix-command-line-mistakes.html) 👀 /etc - ➔ [Linux shell scripting tutorial](https://bash.cyberciti.biz/guide/Main_Page "Linux Shell Scripting Tutorial Wiki") - ➔ [RSS/Feed](https://www.cyberciti.com/atom/atom.xml "Get updates using RSS feed") - ➔ [About nixCraft](https://www.cyberciti.biz/tips/about-us "About nixCraft") ©2002-2025 nixCraft • [Privacy](https://www.cyberciti.biz/tips/privacy "Privacy policy") • [ToS](https://www.cyberciti.biz/tips/disclaimer "Term of Service") • [Contact/Email](https://www.cyberciti.biz/tips/contact-us "Contact us via Email") • Corporate patron [Cloudflare](https://www.cyberciti.biz/tips/nixcraft-sponsors "Corporate patron")