🕷️ Crawler Inspector

Menu [](https://www.howtogeek.com/) Sign in now Close - - [Desktop](https://www.howtogeek.com/category/desktop/) Submenu - [Windows](https://www.howtogeek.com/category/windows/) - [Mac](https://www.howtogeek.com/category/mac/) - [Linux](https://www.howtogeek.com/category/linux/) - [Chromebook](https://www.howtogeek.com/category/chromebook-chrome-os/) - [Microsoft](https://www.howtogeek.com/category/microsoft/) - [Programming](https://www.howtogeek.com/category/programming/) - [Mobile](https://www.howtogeek.com/category/mobile/) Submenu - [Android](https://www.howtogeek.com/category/android/) - [iPhone](https://www.howtogeek.com/category/ios/) - [Cellular Carriers](https://www.howtogeek.com/category/cellular-carriers/) - [Gaming](https://www.howtogeek.com/category/video-games/) - [Streaming](https://www.howtogeek.com/category/streaming/) Submenu - [Audio/Video](https://www.howtogeek.com/category/audio/) - [Web](https://www.howtogeek.com/category/web/) Submenu - [Cyber Security](https://www.howtogeek.com/category/cybersecurity/) - [Google](https://www.howtogeek.com/tag/google/) - [Automotive](https://www.howtogeek.com/category/automotive/) - [Hobbies](https://www.howtogeek.com/category/hobbies/) - Science Submenu - [Space](https://www.howtogeek.com/category/space/) - [Cutting Edge](https://www.howtogeek.com/category/cutting-edge/) - [News](https://www.howtogeek.com/news/) - [Reviews](https://www.howtogeek.com/category/product-reviews/) - [Buying Guides](https://www.howtogeek.com/buying-guides/) - [Deals](https://www.howtogeek.com/tag/deals/) - [Sign in](https://www.howtogeek.com/815778/bash-for-loops-examples/) - [Newsletter](https://www.howtogeek.com/page/newsletter/) Menu [](https://www.howtogeek.com/) Follow Followed Like More Action Sign in now [iPhone](https://www.howtogeek.com/category/ios/) [Windows](https://www.howtogeek.com/category/windows/) [Linux](https://www.howtogeek.com/category/linux/) [Open Source Tools](https://www.howtogeek.com/tag/open-source/) [Android](https://www.howtogeek.com/category/android/) [Streaming](https://www.howtogeek.com/category/streaming/) [Microsoft Excel](https://www.howtogeek.com/tag/microsoft-excel/) [Deals](https://www.howtogeek.com/tag/deals/) Close # 9 Examples of for Loops in Linux Bash Scripts  Credit: Hannah Stryker / How-To Geek [](https://www.howtogeek.com/author/david-mckay/) By [Dave McKay](https://www.howtogeek.com/author/david-mckay/) Updated Oct 30, 2023 Dave McKay first used computers when punched paper tape was in vogue, and he has been programming ever since. After over 30 years in the IT industry, he became a full-time technology journalist. His first published article, describing macros in 6502 assembly language, was published in the December 1985 edition of the UK magazine Personal Computer World. His work has appeared on How-To Geek since March 2019. Despite graduating from Sheffield University as an archaeologist, during his career he's worked as a freelance programmer, manager of an international software development team, project manager for IT installations, and a Data Protection Officer. Dave is a Linux evangelist and open source advocate. Since 1997, all of Dave's computers have run Linux. He is a frequent guest speaker at national conferences, usually talking about topics such as artificial intelligence, data protection legislation, and cybersecurity. Expect detailed how-to's, distribution reviews, and Linux-centric editorials. [Sign in to your How-To Geek account]() Jump links ### Jump Links - [The for Loop](https://www.howtogeek.com/815778/bash-for-loops-examples/#the-for-loop) - [Simple for Loops](https://www.howtogeek.com/815778/bash-for-loops-examples/#simple-for-loops) - [C-like for Loops](https://www.howtogeek.com/815778/bash-for-loops-examples/#c-like-for-loops) - [for Loops Using Word Arrays](https://www.howtogeek.com/815778/bash-for-loops-examples/#for-loops-using-word-arrays) - [for Loops Using Associative Arrays](https://www.howtogeek.com/815778/bash-for-loops-examples/#for-loops-using-associative-arrays) - [Iterating Over the output of Commands](https://www.howtogeek.com/815778/bash-for-loops-examples/#iterating-over-the-output-of-commands) - [The Dazzling for Loop](https://www.howtogeek.com/815778/bash-for-loops-examples/#the-dazzling-for-loop) follow Follow followed Followed Like Like Log in Here is a fact-based summary of the story contents: Try something different: Show me the facts Explain it like I’m 5 Give me a lighthearted recap ### Jump Links - [The for Loop](https://www.howtogeek.com/815778/bash-for-loops-examples/#the-for-loop) - [Simple for Loops](https://www.howtogeek.com/815778/bash-for-loops-examples/#simple-for-loops) - [C-like for Loops](https://www.howtogeek.com/815778/bash-for-loops-examples/#c-like-for-loops) - [for Loops Using Word Arrays](https://www.howtogeek.com/815778/bash-for-loops-examples/#for-loops-using-word-arrays) - [for Loops Using Associative Arrays](https://www.howtogeek.com/815778/bash-for-loops-examples/#for-loops-using-associative-arrays) - [Iterating Over the output of Commands](https://www.howtogeek.com/815778/bash-for-loops-examples/#iterating-over-the-output-of-commands) - [The Dazzling for Loop](https://www.howtogeek.com/815778/bash-for-loops-examples/#the-dazzling-for-loop) The versatile Bash `for` loop does much more than loop around a set number of times. We describe its many variants so you can use them successfully in your own Linux scripts. ## The for Loop All scripting and programming languages have some way of handling loops. A loop is a section of code that you want to have executed repeatedly. Rather than type the same set of instructions into your [script](https://www.howtogeek.com/808593/bash-script-examples/), again and again, a loop will repeat one section of code over and over for you. The Bash `for` loop is very flexible. It can work with numbers, words, arrays, command line variables, or the output of other commands. These are used in the header of the loop. The header dictates what the loop is working with---numbers or strings, for example---and what the end condition is that will stop the looping. The body of the loop contains the code that you want to have repeated. It holds what you want the loop to do. The loop body can contain any valid script command. A variable called the loop counter or iterator is used to step through a range of values or a list of data items. For each loop, the iterator takes on the value of the next number, string, or whatever data type the loop is iterating over. This allows the loop to work with the values of each of the data items in turn, or even in some cases to manipulate the data items themselves. ## Simple for Loops If you're looking to write your first for loop, these simple examples will get you started. ### for Loops using Numerical Lists You can run a `for` loop on the command line. This command creates and executes a simple `for` loop. The iterator is a variable called `i`. We're going to assign `i` to be each of the values in the list of numbers, in turn. The body of the loop is going to print that value to the terminal window. The condition that ends this loop is when `i` has iterated across the entire list of numbers. ``` for i in 1 2 3 4 5; do echo $i; done ```  It's important to note here that the variable `i` is increased by one each time the loop spins round, but that's because the list of numbers goes up by one each time. This list of numbers starts at 3 and goes up in steps of two, then arbitrarily leaps to 44. ``` for i in 3 5 7 9 11 44; do echo $i; done ```  It makes no difference to the `for` loop. It starts at one end of the list and uses each value in turn, until all the values in the list have been used. Nor do the numbers need to be in ascending order. They can be in any order. ``` for i in 3 43 44 11 9; do echo $i; done ```  ### for Loops Using Word Lists We can just as easily do the same with words. Copy the text of the script into an editor and save it as "word-list.sh." ``` ``` You'll need to use `chmod` to make the script executable, and any other script you copy out of this article. Just substitute the name of the script each time you use the `chmod` command. ``` chmod +x word-list.sh ```  Let's run the script. ``` ./word-list.sh ```  Just as it did with the numbers, the iterator---in this example, the variable `word`\---works its way through the list of data items until it reaches the end of the list. The loop body accesses the value in the `word` variable and so each word in the list gets processed. ### for Loops with Number Ranges If you wanted a `for` loop to run 100 times it would be a pretty tiresome affair to have to type in a sequence of 100 numbers in the loop header. Number ranges let you specify the first and last number only. This script is "number-range.sh." ``` ``` The number range is defined within curly brackets "`{}`" with two periods "`..`" separating the numbers that start and end the range. Make sure you don't include any whitespace in the range definition. This is how it runs: ``` ./number-range.sh ```  You can include another number that defines the step size the iterator should use to walk through the numbers in the range. This script, "number-range2.sh" will use a range of 0 to 32, and a step size of 4. ``` ``` The iterator steps through the number range in jumps of four. ``` ./number-range2.sh ```  ### for Loops Using Filenames Because we can process lists of words, we can get our scripts to work with filenames. This script is called "filenames.sh." ``` ``` It would be pretty pointless to have a script that only does what `ls` can do, but it does demonstrate how to access filenames inside the loop body. ``` ./filenames.sh ```  In a similar way to using the number range, we can use a file pattern in the loop header to specify the files we want to process. This avoids a lot of typing and means we don't need to know in advance the names of the files. This script is called "filenames2.sh." We've replaced the list of filenames with the filename pattern "\*.sh" to have the script report on all script files in the current directory. ``` ``` Here's the output. ``` ./filenames2.sh ```  ### for Loops Using Command Line Parameters We can add some more flexibility by passing in the filename pattern on the command line. The `$*` variable represents all of the command line parameters passed to the script. This is "filenames3.sh." ``` ``` We'll ask for filenames that begin with "n" and have an SH extension. ``` ./filenames3.sh n*.sh ```  We can also pass in more than one pattern at a time. ``` ./filenames3.sh n*.sh .bashrc ```  The iterator variable `file` takes on the value of each of the command line parameters. Filename patterns are expanded, and all of the filenames are processed in the loop body. ## C-like for Loops Bash supports the classic three-term for loop, such as those found in the C programming language. They're called three-term for loops because there are three terms in the loop header. - The initial value of the loop iterator. - The test for whether the loop continues or ends. - The incrementing---or decrementing---of the iterator. This script is "c-like.sh." The iterator `I` is set to 1 at the start of the loop, and the loop will run for as long as the statement " `i<=10` " is true. As soon as `i` reaches 11, the `for` loop will stop. The iterator is being increased by one, every revolution of the loop. ``` ``` Let's run this script. ``` ./c-like.sh ```  The C-like `for` loop permits the easy creation of `for` loops that have slightly odd requirements. This loop starts at 15, and counts backward in steps of 3. This is "c-like2.sh" ``` ``` When we run it, it should jump backward in steps of three. ``` ./c-like2.sh ```  ### Infinite for Loops You can also use this format of `for` loop to create an infinite loop. All you need do is remove all of the elements from the loop header, like this. This is "infinite.sh." ``` ``` You'll need to hit Ctrl+C to stop the loop. ``` ./infinite.sh ```  ## for Loops Using Word Arrays We can easily iterate through an array of words. We need to provide the name of the array in the loop header, and the iterator will walk through all entries in the array. This is "word-array.sh." ``` ``` All the distributions are listed for us. ``` ./word-array.sh ```  ### The continue Command If you want the loop to step over a particular entry, test whether the iterator matches that entry and use the `continue` command. The `continue` command abandons the current spin of the loop. It increments the iterator and starts the next spin of the loop---assuming the entry you want to skip over isn't the last item in the list. This is "word-array2.sh." It steps over the "Arch" array entry but processes all other array members. ``` ``` "Arch" doesn't appear in the terminal window. ``` ./word-array2.sh ```  ### The break Command The `break` command breaks out of the loop and prevents any more processing. This is "word-array3.sh." It's the same as the previous script with `continue` replaced by `break`. ``` ``` When the iterator contains "Arch" the for loop abandons any more processing. ``` ./word-array3.sh ```  ## for Loops Using Associative Arrays In Bash 4 and higher, associative arrays allow you to create lists of key-value pairs that can be searched by the key or by the value. Because of the two-way relationship between the key and the value, they're also called data dictionaries. We can iterate through an associative array using a `for` loop. This script is "associative.sh." It defines an associative array with four entries in it, one for each of "dog", "cat", "robin" , and "human." These are the keys. The values are the (default) number of legs they each have. ``` ``` The iterator is called `legs` . Note that the loop header contains an "`!`" exclamation point. This is not acting as the logical NOT operator, it's part of the associative array syntax. It is required to search through the array. The body of the loop performs a string comparison test. If the value of the array member is "Two-legged", it prints the key value to the terminal window. When we run it, the script prints the two-legged creatures. ``` ./associative.sh ```  ## Iterating Over the output of Commands If you have a command or sequence of commands that produce a list of something, such as filenames, you can iterate through them with a `for` loop. You need to watch out for unexpected filename expansions, but in simple cases it is fine. This script is "command.sh." it uses `ls` and `wc` to provide a sorted list of script file names, together with their line, word, and byte counts. ``` #!/bin/bashfor i in $(ls *.sh | sort);do echo $(wc $i)done ``` When we run it we get the statistics for each file, with the files listed in alphabetical order. ``` ./command.sh ```  ## The Dazzling for Loop The `for` loop is a versatile and easily understood scripting tool. But as flexible as it is, don't forget that other loops exist for a reason. Don't be dazzled into thinking the `for` loop is all you'll ever need. Related: [How to Process a File Line by Line in a Linux Bash Script](https://www.howtogeek.com/709838/how-to-process-a-file-line-by-line-in-a-linux-bash-script/) The `while` loop, for example, is much better suited for certain things than the `for` loop, such as [reading lines from a file](https://www.howtogeek.com/709838/how-to-process-a-file-line-by-line-in-a-linux-bash-script/). Writing good scripts means using the most suitable tool for the task at hand. The `for` loop is a great tool to have in your toolbox of tricks. - [Linux](https://www.howtogeek.com/category/linux/ "Linux") - [Linux & macOS Terminal](https://www.howtogeek.com/tag/terminal/ "Linux & macOS Terminal") Follow Followed Like Share [Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.howtogeek.com%2F815778%2Fbash-for-loops-examples%2F%2F&src=sdkpreparse) [X](https://twitter.com/intent/tweet?text=9%20Examples%20of%20for%20Loops%20in%20Linux%20Bash%20Scripts&url=https%3A%2F%2Fwww.howtogeek.com%2F815778%2Fbash-for-loops-examples%2F) [LinkedIn](https://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.howtogeek.com%2F815778%2Fbash-for-loops-examples%2F&title=9%20Examples%20of%20for%20Loops%20in%20Linux%20Bash%20Scripts&source=www.howtogeek.com&summary=How%20to%20repeat%20yourself%2C%20elegantly.) [Reddit](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.howtogeek.com%2F815778%2Fbash-for-loops-examples%2F) [Flipboard](http://share.flipboard.com/bookmarklet/popout?v=2&title=9%20Examples%20of%20for%20Loops%20in%20Linux%20Bash%20Scripts&url=https%3A%2F%2Fwww.howtogeek.com%2F815778%2Fbash-for-loops-examples%2F&utm_campaign=tools&utm_medium=article-share&utm_source=www.howtogeek.com) [Copy link]() [Email](<mailto:?Subject=9 Examples of for Loops in Linux Bash Scripts&Body=Check%20this%20out%21%0Ahttps://www.howtogeek.com/815778/bash-for-loops-examples/>) Readers like you help support How-To Geek. When you make a purchase using links on our site, we may earn an affiliate commission. [Read More](https://www.valnetinc.com/en/terms-of-use). Close Recommended [](https://www.howtogeek.com/devops/automate-inputs-to-linux-scripts-with-the-expect-command/) May 24, 2021 ### [Automate Inputs to Linux Scripts With the expect Command](https://www.howtogeek.com/devops/automate-inputs-to-linux-scripts-with-the-expect-command/ "Automate Inputs to Linux Scripts With the expect Command") [](https://www.howtogeek.com/things-nobody-tells-you-about-switching-to-linux-from-windows/) 3 days ago ### [5 Things Nobody Tells You About Switching to Linux from Windows](https://www.howtogeek.com/things-nobody-tells-you-about-switching-to-linux-from-windows/ "5 Things Nobody Tells You About Switching to Linux from Windows") [](https://www.howtogeek.com/corsair-latest-pc-case-is-almost-all-glass/) 19 hours ago ### [Corsair's Latest PC Case Is Almost All Glass](https://www.howtogeek.com/corsair-latest-pc-case-is-almost-all-glass/ "Corsair's Latest PC Case Is Almost All Glass") [](https://www.howtogeek.com/everything-to-know-about-spartacus-house-of-ashur/) 21 hours ago ### [Everything You Need to Know About Spartacus: House of Ashur](https://www.howtogeek.com/everything-to-know-about-spartacus-house-of-ashur/ "Everything You Need to Know About Spartacus: House of Ashur") - ### Desktop - ### Mobile [](https://www.howtogeek.com/437958/how-to-use-the-chmod-command-on-linux/) ##### [How to Use the chmod Command on Linux](https://www.howtogeek.com/437958/how-to-use-the-chmod-command-on-linux/ "How to Use the chmod Command on Linux") 2 hours ago [](https://www.howtogeek.com/the-best-earbuds-for-iphone-just-got-even-better/) ##### [The Best Earbuds for iPhone Just Got Even Better](https://www.howtogeek.com/the-best-earbuds-for-iphone-just-got-even-better/ "The Best Earbuds for iPhone Just Got Even Better") 3 hours ago [](https://www.howtogeek.com/this-logitech-keyboard-is-powered-by-light/) ##### [This Logitech Keyboard Is Powered By Light](https://www.howtogeek.com/this-logitech-keyboard-is-powered-by-light/ "This Logitech Keyboard Is Powered By Light") 6 hours ago [See More](https://www.howtogeek.com/category/desktop/) [](https://www.howtogeek.com/this-is-why-the-iphone-17-pro-is-scratching-so-much/) ##### [This Is Why The iPhone 17 Pro Is Scratching So Much](https://www.howtogeek.com/this-is-why-the-iphone-17-pro-is-scratching-so-much/ "This Is Why The iPhone 17 Pro Is Scratching So Much") 24 minutes ago [](https://www.howtogeek.com/foam-ear-tips-are-a-trendy-upgrade-but-do-they-really-make-your-earbuds-better/) ##### [Foam Ear Tips Are a Trendy Upgrade, but Do They Really Make Your Earbuds Better?](https://www.howtogeek.com/foam-ear-tips-are-a-trendy-upgrade-but-do-they-really-make-your-earbuds-better/ "Foam Ear Tips Are a Trendy Upgrade, but Do They Really Make Your Earbuds Better?") 17 hours ago [](https://www.howtogeek.com/you-can-now-tell-google-photos-how-to-edit-a-photo-for-you/) ##### [You Can Now Tell Google Photos How to Edit a Photo for You](https://www.howtogeek.com/you-can-now-tell-google-photos-how-to-edit-a-photo-for-you/ "You Can Now Tell Google Photos How to Edit a Photo for You") 20 hours ago [See More](https://www.howtogeek.com/category/mobile/) Trending Now [](https://www.howtogeek.com/i-cleaned-my-pc-and-realized-i-should-be-doing-this-way-more-often/) ##### [I Cleaned My PC and Realized I Should Be Doing This Way More Often](https://www.howtogeek.com/i-cleaned-my-pc-and-realized-i-should-be-doing-this-way-more-often/ "I Cleaned My PC and Realized I Should Be Doing This Way More Often") [](https://www.howtogeek.com/viture-luma-pro-xr-glasses-review/) ##### [VITURE's Luma Pro Brings Greater Clarity and Brightness to XR Glasses](https://www.howtogeek.com/viture-luma-pro-xr-glasses-review/ "VITURE's Luma Pro Brings Greater Clarity and Brightness to XR Glasses") [](https://www.howtogeek.com/787217/how-to-edit-environment-variables-on-windows-10-or-11/) ##### [How to Edit Environment Variables on Windows 11](https://www.howtogeek.com/787217/how-to-edit-environment-variables-on-windows-10-or-11/ "How to Edit Environment Variables on Windows 11") [](https://www.howtogeek.com/) - [Join Our Team](https://www.howtogeek.com/work-with-us/) - [Our Audience](https://www.howtogeek.com/page/advertise/) - [About Us](https://www.howtogeek.com/page/about/) - [Press & Events](https://www.howtogeek.com/page/press-events/) - [Contact Us](https://www.howtogeek.com/contact/) - Follow Us [](https://www.valnetinc.com/en/) - [Advertising](https://www.valnetinc.com/en/advertising) - [Careers](https://www.valnetinc.com/en/careers) - [Terms](https://www.valnetinc.com/en/terms-of-use) - [Privacy](https://www.howtogeek.com/page/our-privacy-policy/) - [Policies](https://www.howtogeek.com/page/our-editorial-guidelines/) [How-To Geek](https://www.howtogeek.com/) is part of the [Valnet Publishing Group](https://www.valnetinc.com/en/) Copyright © 2025 Valnet Inc.