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Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 152 (from laksa129)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa152.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://en.wikipedia.org/wiki/Job_control_(Unix)\')), getAhrefsUnparsedNoserviceFromURL(\'https://en.wikipedia.org/wiki/Job_control_(Unix)\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/en.wikipedia.org\/wiki\/Job_control_(Unix)","crawl_time":1774446058,"first_indexed_time":1435703631,"http_code":200,"src_unparsed":"org,wikipedia!en,\/wiki\/Job_control_(Unix) s443","src_root_hash":"17790707453426894952","history_drop_reason":null,"meta_title":"Job control (Unix) - Wikipedia","meta_descriptions":[],"attrs_boilerpipe_text":"From Wikipedia, the free encyclopedia\nThis article is about job control on a Unix-based system. For the general computing term, see\njob control\n.\nIn a\nUnix\nor\nUnix-like\noperating system\n,\njob control\nrefers to controlling a\nprocess group\nas a\njob\nvia a\nshell\n.\n[\n1\n]\nControl features include suspend, resume, and terminate, and more advanced features can be performed by sending a\nsignal\nto a job. Job control allows a user to manage processing in the Unix-based\nmultiprocessing\nenvironment, and is distinct from\ngeneral computing job control\n.\nJob control was first implemented in the\nC shell\nby Jim Kulp,\n[\n2\n]\nthen at\nIIASA\nin Austria, making use of features of the 4.1\nBSD\nkernel.\nThe\nKornShell\n, developed at\nBell Labs\n, adopted it and it was later incorporated into the SVR4 version of the\nBourne shell\n, and exists in most modern Unix shells.\nA job encompasses all of the processes that start for the handling of a shell\ncommand line\n. A simple command line may start just one process, but a command line may result in multiple processes since a process can create\nchild processes\n, and a command line can specify a\npipeline\nof multiple commands. For example, the following command line selects lines containing the text \"title\", sorts them alphabetically, and displays the result in a\nterminal pager\n:\ngrep title somefile.txt | sort | less\n. This creates at least three processes: one for\ngrep\n, one for\nsort\n, and one for\nless\n. Job control allows the shell to control these processes as one entity.\nA job is identified by a numeric\njob ID\n, a.k.a.\njob number\nwhich is classified as a\nhandle\nsince it is an abstract reference to a\nresource\n(a process group). An ID value, prefixed with\n%\n, can be used with a job control command to specify a job. The special references\n%%\nand\n%+\nrefer to the default job, the one that would be selected if none were specified.\n[\n3\n]\nBash documentation refers to a reference (starting with\n%\n) as a\njobspec\n(short for job specification).\n[\n4\n]\nJob control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script.\nForeground\/background\n[\nedit\n]\nBy default, a job runs in the foreground where it uses\ninteractive input and output\n. The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may\nredirect\noutput for a background job to prevent this.\nPOSIX\nspecifies the\nuser interface\nto job control – modeled on the Korn shell.\n[\n5\n]\nThe commands are typically implemented as\nshell builtins\n, not separate\nprograms\n.\nStart in background\nIf a command line ends with\n&\n, then the job starts in the background.\nPause foreground job\nThe foreground job can be paused by pressing\nCtrl\n+\nZ\n. In this state, a job can be resumed in the background via\nbg\nor resumed in the foreground via\nfg\n.\nCommand\nfg\nCommand\nfg\n(short for\nf\nore\ng\nround) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via\nCtrl\n+\nZ\n), then this command resumes that job.\nCommand\nwait\nCommand\nwait\npauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified.\n[\n6\n]\nCommand\nbg\nCommand\nbg\n(short for\nb\nack\ng\nround) moves the paused foreground job to the background and resumes it.\nCommand\njobs\nCommand\njobs\nreports information about each background job including ID, command line and running status (stopped or running).\nThe\ninterprocess communication\nof job control is implemented via\nsignals\n.\nTypically, a shell maintains information about background jobs in a job table. When an\ninteractive session\nends (i.e. user\nlogs out\n), the shell sends signal\nSIGHUP\nto all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command\ndisown\nthat removes a job from the job table. The process group becomes an\norphan\n. The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a\ndaemon\nowned directly by the root process\ninit\n. The POSIX command\nnohup\nprovides an alternate way to prevent a job from being terminated by the shell.\nSuspending the foreground job (via\nCtrl\n+\nZ\n) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored.\nWhen the user presses\nCtrl\n+\nC\n, the shell sends signal\nSIGINT\n(interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal.\nWhen a stopped job is resumed (via\nbg\nor\nfg\n), the shell redirects\nInput\/output\nand resumes it by sending signal SIGCONT to it.\nA background process that attempts to read from or write to its\ncontrolling terminal\nis sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default.\nIn bash, the\nkill\nbuiltin (not\n\/bin\/kill\n) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group.\nkill\ncan send any signal to a job; however, if the intent is to rid the system of the processes, the signals\nSIGKILL\nand\nSIGTERM\n(the default) are probably the most applicable.\n^\nIEEE Std 1003.1-2001,\nSection 3.201, Job\nArchived\n2019-08-01 at the\nWayback Machine\n^\nForeword by\nBill Joy\nin\nAnderson, Gail; Paul Anderson (1986).\nThe UNIX C Shell Field Guide\n. Prentice-Hall. p. xvii.\nISBN\n \n0-13-937468-X\n.\n^\nIEEE Std 1003.1-2001,\nSection 3.203, Job Control Job ID\nArchived\n2010-10-09 at the\nWayback Machine\n^\n\"7.1 Job Control Basics\"\n.\nArchived\nfrom the original on 2016-08-02\n. Retrieved\n2016-07-22\n.\n^\nbg\n – Shell and Utilities Reference,\nThe Single UNIX Specification\n, Version 5 from\nThe Open Group\n;\nfg\n – Shell and Utilities Reference,\nThe Single UNIX Specification\n, Version 5 from\nThe Open Group\n.\n^\nKerrisk, Michael (Feb 2, 2025).\n\"wait(1p) — Linux manual page\"\n.\nman7.org\n.\nArchived\nfrom the original on May 16, 2025\n. Retrieved\nMay 13,\n2025\n.\nMarshall Kirk McKusick\nand George V. Neville-Neil (2004-08-02).\n\"FreeBSD Process Management: Process Groups and Sessions\"\n.\nThe Design and Implementation of the FreeBSD Operating System\n. Addison Wesley.\nISBN\n \n0-201-70245-2\n.\n\"Job Control\",\nBash Reference Manual","attrs_markdown":"[Jump to content](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#bodyContent)\n\nMain menu\n\nMain menu\n\nmove to sidebar\n\nhide\n\nNavigation\n\n- [Main page](https:\/\/en.wikipedia.org\/wiki\/Main_Page \"Visit the main page [z]\")\n- [Contents](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Contents \"Guides to browsing Wikipedia\")\n- [Current events](https:\/\/en.wikipedia.org\/wiki\/Portal:Current_events \"Articles related to current events\")\n- [Random article](https:\/\/en.wikipedia.org\/wiki\/Special:Random \"Visit a randomly selected article [x]\")\n- [About Wikipedia](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:About \"Learn about Wikipedia and how it works\")\n- [Contact us](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Contact_us \"How to contact Wikipedia\")\n\nContribute\n\n- [Help](https:\/\/en.wikipedia.org\/wiki\/Help:Contents \"Guidance on how to use and edit Wikipedia\")\n- [Learn to edit](https:\/\/en.wikipedia.org\/wiki\/Help:Introduction \"Learn how to edit Wikipedia\")\n- [Community portal](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Community_portal \"The hub for editors\")\n- [Recent changes](https:\/\/en.wikipedia.org\/wiki\/Special:RecentChanges \"A list of recent changes to Wikipedia [r]\")\n- [Upload file](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:File_upload_wizard \"Add images or other media for use on Wikipedia\")\n- [Special pages](https:\/\/en.wikipedia.org\/wiki\/Special:SpecialPages \"A list of all special pages [q]\")\n\n[![](https:\/\/en.wikipedia.org\/static\/images\/icons\/enwiki-25.svg) ![Wikipedia](https:\/\/en.wikipedia.org\/static\/images\/mobile\/copyright\/wikipedia-wordmark-en-25.svg) ![The Free Encyclopedia](https:\/\/en.wikipedia.org\/static\/images\/mobile\/copyright\/wikipedia-tagline-en-25.svg)](https:\/\/en.wikipedia.org\/wiki\/Main_Page)\n\n[Search](https:\/\/en.wikipedia.org\/wiki\/Special:Search \"Search Wikipedia [f]\")\n\nAppearance\n\n- [Donate](https:\/\/donate.wikimedia.org\/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en)\n- [Create account](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:CreateAccount&returnto=Job+control+%28Unix%29 \"You are encouraged to create an account and log in; however, it is not mandatory\")\n- [Log in](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:UserLogin&returnto=Job+control+%28Unix%29 \"You're encouraged to log in; however, it's not mandatory. [o]\")\n\nPersonal tools\n\n- [Donate](https:\/\/donate.wikimedia.org\/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en)\n- [Create account](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:CreateAccount&returnto=Job+control+%28Unix%29 \"You are encouraged to create an account and log in; however, it is not mandatory\")\n- [Log in](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:UserLogin&returnto=Job+control+%28Unix%29 \"You're encouraged to log in; however, it's not mandatory. [o]\")\n\n## Contents\nmove to sidebar\n\nhide\n\n- [(Top)](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\))\n- [1 Job](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Job)\n- [2 Job ID](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Job_ID)\n- [3 Foreground\/background](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Foreground\/background)\n- [4 Control](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Control)\n- [5 Signals](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Signals)\n- [6 References](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#References)\n- [7 Further reading](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#Further_reading)\n- [8 External links](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#External_links)\n\nToggle the table of contents\n\n# Job control (Unix)\n7 languages\n\n- [Català](https:\/\/ca.wikipedia.org\/wiki\/Control_de_tasques_\\(Unix\\) \"Control de tasques (Unix) – Catalan\")\n- [Čeština](https:\/\/cs.wikipedia.org\/wiki\/%C5%98%C3%ADzen%C3%AD_%C3%BAloh_\\(Unix\\) \"Řízení úloh (Unix) – Czech\")\n- [Deutsch](https:\/\/de.wikipedia.org\/wiki\/Job_control \"Job control – German\")\n- [Français](https:\/\/fr.wikipedia.org\/wiki\/SIGTSTP \"SIGTSTP – French\")\n- [한국어](https:\/\/ko.wikipedia.org\/wiki\/Jobs_\\(%EC%9C%A0%EB%8B%89%EC%8A%A4\\) \"Jobs (유닉스) – Korean\")\n- [Português](https:\/\/pt.wikipedia.org\/wiki\/Controle_de_trabalhos_\\(Unix\\) \"Controle de trabalhos (Unix) – Portuguese\")\n- [Русский](https:\/\/ru.wikipedia.org\/wiki\/%D0%A3%D0%BF%D1%80%D0%B0%D0%B2%D0%BB%D0%B5%D0%BD%D0%B8%D0%B5_%D0%B7%D0%B0%D0%B4%D0%B0%D0%BD%D0%B8%D1%8F%D0%BC%D0%B8 \"Управление заданиями – Russian\")\n\n[Edit links](https:\/\/www.wikidata.org\/wiki\/Special:EntityPage\/Q6206712#sitelinks-wikipedia \"Edit interlanguage links\")\n\n- [Article](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\) \"View the content page [c]\")\n- [Talk](https:\/\/en.wikipedia.org\/wiki\/Talk:Job_control_\\(Unix\\) \"Discuss improvements to the content page [t]\")\n\nEnglish\n\n- [Read](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\))\n- [Edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit \"Edit this page [e]\")\n- [View history](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=history \"Past revisions of this page [h]\")\n\nTools\n\nTools\n\nmove to sidebar\n\nhide\n\nActions\n\n- [Read](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\))\n- [Edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit \"Edit this page [e]\")\n- [View history](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=history)\n\nGeneral\n\n- [What links here](https:\/\/en.wikipedia.org\/wiki\/Special:WhatLinksHere\/Job_control_\\(Unix\\) \"List of all English Wikipedia pages containing links to this page [j]\")\n- [Related changes](https:\/\/en.wikipedia.org\/wiki\/Special:RecentChangesLinked\/Job_control_\\(Unix\\) \"Recent changes in pages linked from this page [k]\")\n- [Upload file](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:File_Upload_Wizard \"Upload files [u]\")\n- [Permanent link](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&oldid=1336330596 \"Permanent link to this revision of this page\")\n- [Page information](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=info \"More information about this page\")\n- [Cite this page](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:CiteThisPage&page=Job_control_%28Unix%29&id=1336330596&wpFormIdentifier=titleform \"Information on how to cite this page\")\n- [Get shortened URL](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FJob_control_%28Unix%29)\n\nPrint\/export\n\n- [Download as PDF](https:\/\/en.wikipedia.org\/w\/index.php?title=Special:DownloadAsPdf&page=Job_control_%28Unix%29&action=show-download-screen \"Download this page as a PDF file\")\n- [Printable version](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&printable=yes \"Printable version of this page [p]\")\n\nIn other projects\n\n- [Wikidata item](https:\/\/www.wikidata.org\/wiki\/Special:EntityPage\/Q6206712 \"Structured data on this page hosted by Wikidata [g]\")\n\nAppearance\n\nmove to sidebar\n\nhide\n\nFrom Wikipedia, the free encyclopedia\n\nControl of jobs in a Unix shell\n\nThis article is about job control on a Unix-based system. For the general computing term, see [job control](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(computing\\) \"Job control (computing)\").\n\nIn a [Unix](https:\/\/en.wikipedia.org\/wiki\/Unix \"Unix\") or [Unix-like](https:\/\/en.wikipedia.org\/wiki\/Unix-like \"Unix-like\") [operating system](https:\/\/en.wikipedia.org\/wiki\/Operating_system \"Operating system\"), **job control** refers to controlling a [process group](https:\/\/en.wikipedia.org\/wiki\/Process_group \"Process group\") as a [job](https:\/\/en.wikipedia.org\/wiki\/Job_\\(computing\\) \"Job (computing)\") via a [shell](https:\/\/en.wikipedia.org\/wiki\/Unix_shell \"Unix shell\").[\\[1\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-1) Control features include suspend, resume, and terminate, and more advanced features can be performed by sending a [signal](https:\/\/en.wikipedia.org\/wiki\/Signal_\\(IPC\\) \"Signal (IPC)\") to a job. Job control allows a user to manage processing in the Unix-based [multiprocessing](https:\/\/en.wikipedia.org\/wiki\/Multiprocessing \"Multiprocessing\") environment, and is distinct from [general computing job control](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(computing\\) \"Job control (computing)\").\n\nJob control was first implemented in the [C shell](https:\/\/en.wikipedia.org\/wiki\/C_shell \"C shell\") by Jim Kulp,[\\[2\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-2) then at [IIASA](https:\/\/en.wikipedia.org\/wiki\/IIASA \"IIASA\") in Austria, making use of features of the 4.1[BSD](https:\/\/en.wikipedia.org\/wiki\/BSD \"BSD\") kernel. The [KornShell](https:\/\/en.wikipedia.org\/wiki\/KornShell \"KornShell\"), developed at [Bell Labs](https:\/\/en.wikipedia.org\/wiki\/Bell_Labs \"Bell Labs\"), adopted it and it was later incorporated into the SVR4 version of the [Bourne shell](https:\/\/en.wikipedia.org\/wiki\/Bourne_shell \"Bourne shell\"), and exists in most modern Unix shells.\n\n## Job\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=1 \"Edit section: Job\")\\]\n\nA job encompasses all of the processes that start for the handling of a shell [command line](https:\/\/en.wikipedia.org\/wiki\/Command-line_interface \"Command-line interface\"). A simple command line may start just one process, but a command line may result in multiple processes since a process can create [child processes](https:\/\/en.wikipedia.org\/wiki\/Child_process \"Child process\"), and a command line can specify a [pipeline](https:\/\/en.wikipedia.org\/wiki\/Pipeline_\\(Unix\\) \"Pipeline (Unix)\") of multiple commands. For example, the following command line selects lines containing the text \"title\", sorts them alphabetically, and displays the result in a [terminal pager](https:\/\/en.wikipedia.org\/wiki\/Terminal_pager \"Terminal pager\"): `grep title somefile.txt | sort | less`. This creates at least three processes: one for [`grep`](https:\/\/en.wikipedia.org\/wiki\/Grep \"Grep\"), one for `sort`, and one for [`less`](https:\/\/en.wikipedia.org\/wiki\/Less_\\(Unix\\) \"Less (Unix)\"). Job control allows the shell to control these processes as one entity.\n\n## Job ID\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=2 \"Edit section: Job ID\")\\]\n\nA job is identified by a numeric *job ID*, a.k.a. *job number* which is classified as a [handle](https:\/\/en.wikipedia.org\/wiki\/Handle_\\(computing\\) \"Handle (computing)\") since it is an abstract reference to a [resource](https:\/\/en.wikipedia.org\/wiki\/System_resource \"System resource\") (a process group). An ID value, prefixed with `%`, can be used with a job control command to specify a job. The special references `%%` and `%+` refer to the default job, the one that would be selected if none were specified.[\\[3\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-3) Bash documentation refers to a reference (starting with `%`) as a *jobspec* (short for job specification).[\\[4\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-4)\n\nJob control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script.\n\n## Foreground\/background\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=3 \"Edit section: Foreground\/background\")\\]\n\nBy default, a job runs in the foreground where it uses [interactive input and output](https:\/\/en.wikipedia.org\/wiki\/Standard_streams \"Standard streams\"). The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may [redirect](https:\/\/en.wikipedia.org\/wiki\/Redirection_\\(computing\\) \"Redirection (computing)\") output for a background job to prevent this.\n\n## Control\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=4 \"Edit section: Control\")\\]\n\n[POSIX](https:\/\/en.wikipedia.org\/wiki\/POSIX \"POSIX\") specifies the [user interface](https:\/\/en.wikipedia.org\/wiki\/User_interface \"User interface\") to job control – modeled on the Korn shell.[\\[5\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-5) The commands are typically implemented as [shell builtins](https:\/\/en.wikipedia.org\/wiki\/Shell_builtin \"Shell builtin\"), not separate [programs](https:\/\/en.wikipedia.org\/wiki\/Computer_program \"Computer program\").\n\nStart in background\n\nIf a command line ends with `&`, then the job starts in the background.\n\nPause foreground job\n\nThe foreground job can be paused by pressing `Ctrl`\\+` Z`. In this state, a job can be resumed in the background via `bg` or resumed in the foreground via `fg`.\n\nCommand `fg`\n\nCommand `fg` (short for **f**ore**g**round) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via\n\n`Ctrl`\\+` Z`), then this command resumes that job.\n\nCommand `wait`\n\nCommand [`wait`](https:\/\/en.wikipedia.org\/wiki\/Wait_\\(command\\) \"Wait (command)\") pauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified.[\\[6\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-6)\n\nCommand `bg`\n\nCommand `bg` (short for **b**ack**g**round) moves the paused foreground job to the background and resumes it.\n\nCommand `jobs`\n\nCommand `jobs` reports information about each background job including ID, command line and running status (stopped or running).\n\n## Signals\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=5 \"Edit section: Signals\")\\]\n\n|   |   |\n|---|---|\n| [![icon](https:\/\/upload.wikimedia.org\/wikipedia\/en\/thumb\/9\/99\/Question_book-new.svg\/60px-Question_book-new.svg.png)](https:\/\/en.wikipedia.org\/wiki\/File:Question_book-new.svg) | This section **does not [cite](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Citing_sources \"Wikipedia:Citing sources\") any [sources](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Verifiability \"Wikipedia:Verifiability\")**. Please help [improve this section](https:\/\/en.wikipedia.org\/wiki\/Special:EditPage\/Job_control_\\(Unix\\) \"Special:EditPage\/Job control (Unix)\") by [adding citations to reliable sources](https:\/\/en.wikipedia.org\/wiki\/Help:Referencing_for_beginners \"Help:Referencing for beginners\"). Unsourced material may be challenged and [removed](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Verifiability#Burden_of_evidence \"Wikipedia:Verifiability\"). *(February 2020)* *([Learn how and when to remove this message](https:\/\/en.wikipedia.org\/wiki\/Help:Maintenance_template_removal \"Help:Maintenance template removal\"))* |\n\nThe [interprocess communication](https:\/\/en.wikipedia.org\/wiki\/Interprocess_communication \"Interprocess communication\") of job control is implemented via [signals](https:\/\/en.wikipedia.org\/wiki\/Signal_\\(IPC\\) \"Signal (IPC)\").\n\nTypically, a shell maintains information about background jobs in a job table. When an [interactive session](https:\/\/en.wikipedia.org\/wiki\/Login_session \"Login session\") ends (i.e. user [logs out](https:\/\/en.wikipedia.org\/wiki\/Logout \"Logout\")), the shell sends signal [SIGHUP](https:\/\/en.wikipedia.org\/wiki\/SIGHUP \"SIGHUP\") to all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command [`disown`](https:\/\/en.wikipedia.org\/wiki\/Disown_\\(Unix\\) \"Disown (Unix)\") that removes a job from the job table. The process group becomes an [orphan](https:\/\/en.wikipedia.org\/wiki\/Orphan_process \"Orphan process\"). The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a [daemon](https:\/\/en.wikipedia.org\/wiki\/Daemon_\\(computing\\) \"Daemon (computing)\") owned directly by the root process [init](https:\/\/en.wikipedia.org\/wiki\/Init \"Init\"). The POSIX command [`nohup`](https:\/\/en.wikipedia.org\/wiki\/Nohup \"Nohup\") provides an alternate way to prevent a job from being terminated by the shell.\n\nSuspending the foreground job (via `Ctrl`\\+`Z`) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored.\n\nWhen the user presses `Ctrl`\\+`C`, the shell sends signal [SIGINT](https:\/\/en.wikipedia.org\/wiki\/SIGINT_\\(POSIX\\) \"SIGINT (POSIX)\") (interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal.\n\nWhen a stopped job is resumed (via `bg` or `fg`), the shell redirects [Input\/output](https:\/\/en.wikipedia.org\/wiki\/Input\/output \"Input\/output\") and resumes it by sending signal SIGCONT to it.\n\nA background process that attempts to read from or write to its [controlling terminal](https:\/\/en.wikipedia.org\/wiki\/Controlling_terminal \"Controlling terminal\") is sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default.\n\nIn bash, the `kill` builtin (not `\/bin\/kill`) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group. `kill` can send any signal to a job; however, if the intent is to rid the system of the processes, the signals [SIGKILL](https:\/\/en.wikipedia.org\/wiki\/SIGKILL \"SIGKILL\") and [SIGTERM](https:\/\/en.wikipedia.org\/wiki\/SIGTERM \"SIGTERM\") (the default) are probably the most applicable.\n\n## References\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=6 \"Edit section: References\")\\]\n\n1. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-1)** IEEE Std 1003.1-2001, [Section 3.201, Job](http:\/\/pubs.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_201) [Archived](https:\/\/web.archive.org\/web\/20190801165956\/http:\/\/pubs.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_201) 2019-08-01 at the [Wayback Machine](https:\/\/en.wikipedia.org\/wiki\/Wayback_Machine \"Wayback Machine\")\n2. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-2)**\n   Foreword by [Bill Joy](https:\/\/en.wikipedia.org\/wiki\/Bill_Joy \"Bill Joy\") in\n   \n   Anderson, Gail; Paul Anderson (1986). [*The UNIX C Shell Field Guide*](https:\/\/archive.org\/details\/unixcshellfieldg00ande). Prentice-Hall. p. xvii. [ISBN](https:\/\/en.wikipedia.org\/wiki\/ISBN_\\(identifier\\) \"ISBN (identifier)\")\n   \n   [0-13-937468-X](https:\/\/en.wikipedia.org\/wiki\/Special:BookSources\/0-13-937468-X \"Special:BookSources\/0-13-937468-X\")\n   \n   .\n3. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-3)** IEEE Std 1003.1-2001, [Section 3.203, Job Control Job ID](http:\/\/www.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_203) [Archived](https:\/\/web.archive.org\/web\/20101009060625\/http:\/\/www.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_203) 2010-10-09 at the [Wayback Machine](https:\/\/en.wikipedia.org\/wiki\/Wayback_Machine \"Wayback Machine\")\n4. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-4)**\n   [\"7.1 Job Control Basics\"](https:\/\/www.gnu.org\/software\/bash\/manual\/html_node\/Job-Control-Basics.html#Job-Control-Basics). [Archived](https:\/\/web.archive.org\/web\/20160802215912\/http:\/\/www.gnu.org\/software\/bash\/manual\/html_node\/Job-Control-Basics.html#Job-Control-Basics) from the original on 2016-08-02. Retrieved 2016-07-22.\n5. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-5)** `bg` – Shell and Utilities Reference, [The Single UNIX Specification](https:\/\/en.wikipedia.org\/wiki\/Single_Unix_Specification \"Single Unix Specification\"), Version 5 from [The Open Group](https:\/\/en.wikipedia.org\/wiki\/The_Open_Group \"The Open Group\"); `fg` – Shell and Utilities Reference, [The Single UNIX Specification](https:\/\/en.wikipedia.org\/wiki\/Single_Unix_Specification \"Single Unix Specification\"), Version 5 from [The Open Group](https:\/\/en.wikipedia.org\/wiki\/The_Open_Group \"The Open Group\").\n6. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-6)**\n   Kerrisk, Michael (Feb 2, 2025). [\"wait(1p) — Linux manual page\"](https:\/\/www.man7.org\/linux\/man-pages\/man1\/wait.1p.html). *man7.org*. [Archived](https:\/\/web.archive.org\/web\/20250516160332\/https:\/\/www.man7.org\/linux\/man-pages\/man1\/wait.1p.html) from the original on May 16, 2025. Retrieved May 13, 2025.\n\n## Further reading\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=7 \"Edit section: Further reading\")\\]\n\n- [Marshall Kirk McKusick](https:\/\/en.wikipedia.org\/wiki\/Marshall_Kirk_McKusick \"Marshall Kirk McKusick\") and George V. Neville-Neil (2004-08-02). [\"FreeBSD Process Management: Process Groups and Sessions\"](http:\/\/www.informit.com\/articles\/article.aspx?p=366888&seqNum=8). [*The Design and Implementation of the FreeBSD Operating System*](http:\/\/www.informit.com\/title\/0201702452). Addison Wesley. [ISBN](https:\/\/en.wikipedia.org\/wiki\/ISBN_\\(identifier\\) \"ISBN (identifier)\")\n  \n  [0-201-70245-2](https:\/\/en.wikipedia.org\/wiki\/Special:BookSources\/0-201-70245-2 \"Special:BookSources\/0-201-70245-2\")\n  \n  .\n\n## External links\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=8 \"Edit section: External links\")\\]\n\n- \"Job Control\", [*Bash Reference Manual*](https:\/\/web.archive.org\/web\/20060523213233\/http:\/\/cnswww.cns.cwru.edu\/~chet\/bash\/bashref.html)\n\n![](https:\/\/en.wikipedia.org\/wiki\/Special:CentralAutoLogin\/start?useformat=desktop&type=1x1&usesul3=1)\n\nRetrieved from \"<https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_(Unix)&oldid=1336330596>\"\n\n[Category](https:\/\/en.wikipedia.org\/wiki\/Help:Category \"Help:Category\"):\n\n- [Unix](https:\/\/en.wikipedia.org\/wiki\/Category:Unix \"Category:Unix\")\n\nHidden categories:\n\n- [Webarchive template wayback links](https:\/\/en.wikipedia.org\/wiki\/Category:Webarchive_template_wayback_links \"Category:Webarchive template wayback links\")\n- [Articles with short description](https:\/\/en.wikipedia.org\/wiki\/Category:Articles_with_short_description \"Category:Articles with short description\")\n- [Short description is different from Wikidata](https:\/\/en.wikipedia.org\/wiki\/Category:Short_description_is_different_from_Wikidata \"Category:Short description is different from Wikidata\")\n- [Articles needing additional references from February 2020](https:\/\/en.wikipedia.org\/wiki\/Category:Articles_needing_additional_references_from_February_2020 \"Category:Articles needing additional references from February 2020\")\n- [All articles needing additional references](https:\/\/en.wikipedia.org\/wiki\/Category:All_articles_needing_additional_references \"Category:All articles needing additional references\")\n\n- This page was last edited on 3 February 2026, at 04:48 (UTC).\n- Text is available under the [Creative Commons Attribution-ShareAlike 4.0 License](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License \"Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License\"); additional terms may apply. By using this site, you agree to the [Terms of Use](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Policy:Terms_of_Use \"foundation:Special:MyLanguage\/Policy:Terms of Use\") and [Privacy Policy](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Policy:Privacy_policy \"foundation:Special:MyLanguage\/Policy:Privacy policy\"). Wikipedia® is a registered trademark of the [Wikimedia Foundation, Inc.](https:\/\/wikimediafoundation.org\/), a non-profit organization.\n\n- [Privacy policy](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Policy:Privacy_policy)\n- [About Wikipedia](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:About)\n- [Disclaimers](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:General_disclaimer)\n- [Contact Wikipedia](https:\/\/en.wikipedia.org\/wiki\/Wikipedia:Contact_us)\n- [Legal & safety contacts](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Legal:Wikimedia_Foundation_Legal_and_Safety_Contact_Information)\n- [Code of Conduct](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Policy:Universal_Code_of_Conduct)\n- [Developers](https:\/\/developer.wikimedia.org\/)\n- [Statistics](https:\/\/stats.wikimedia.org\/#\/en.wikipedia.org)\n- [Cookie statement](https:\/\/foundation.wikimedia.org\/wiki\/Special:MyLanguage\/Policy:Cookie_statement)\n- [Mobile view](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&mobileaction=toggle_view_mobile)\n\n- [![Wikimedia Foundation](https:\/\/en.wikipedia.org\/static\/images\/footer\/wikimedia.svg)](https:\/\/www.wikimedia.org\/)\n- [![Powered by MediaWiki](https:\/\/en.wikipedia.org\/w\/resources\/assets\/mediawiki_compact.svg)](https:\/\/www.mediawiki.org\/)\n\nSearch\n\nToggle the table of contents\n\nJob control (Unix)\n\n7 languages\n\n[Add topic](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\))","attrs_readable_markdown":"From Wikipedia, the free encyclopedia\n\nThis article is about job control on a Unix-based system. For the general computing term, see [job control](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(computing\\) \"Job control (computing)\").\n\nIn a [Unix](https:\/\/en.wikipedia.org\/wiki\/Unix \"Unix\") or [Unix-like](https:\/\/en.wikipedia.org\/wiki\/Unix-like \"Unix-like\") [operating system](https:\/\/en.wikipedia.org\/wiki\/Operating_system \"Operating system\"), **job control** refers to controlling a [process group](https:\/\/en.wikipedia.org\/wiki\/Process_group \"Process group\") as a [job](https:\/\/en.wikipedia.org\/wiki\/Job_\\(computing\\) \"Job (computing)\") via a [shell](https:\/\/en.wikipedia.org\/wiki\/Unix_shell \"Unix shell\").[\\[1\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-1) Control features include suspend, resume, and terminate, and more advanced features can be performed by sending a [signal](https:\/\/en.wikipedia.org\/wiki\/Signal_\\(IPC\\) \"Signal (IPC)\") to a job. Job control allows a user to manage processing in the Unix-based [multiprocessing](https:\/\/en.wikipedia.org\/wiki\/Multiprocessing \"Multiprocessing\") environment, and is distinct from [general computing job control](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(computing\\) \"Job control (computing)\").\n\nJob control was first implemented in the [C shell](https:\/\/en.wikipedia.org\/wiki\/C_shell \"C shell\") by Jim Kulp,[\\[2\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-2) then at [IIASA](https:\/\/en.wikipedia.org\/wiki\/IIASA \"IIASA\") in Austria, making use of features of the 4.1[BSD](https:\/\/en.wikipedia.org\/wiki\/BSD \"BSD\") kernel. The [KornShell](https:\/\/en.wikipedia.org\/wiki\/KornShell \"KornShell\"), developed at [Bell Labs](https:\/\/en.wikipedia.org\/wiki\/Bell_Labs \"Bell Labs\"), adopted it and it was later incorporated into the SVR4 version of the [Bourne shell](https:\/\/en.wikipedia.org\/wiki\/Bourne_shell \"Bourne shell\"), and exists in most modern Unix shells.\n\nA job encompasses all of the processes that start for the handling of a shell [command line](https:\/\/en.wikipedia.org\/wiki\/Command-line_interface \"Command-line interface\"). A simple command line may start just one process, but a command line may result in multiple processes since a process can create [child processes](https:\/\/en.wikipedia.org\/wiki\/Child_process \"Child process\"), and a command line can specify a [pipeline](https:\/\/en.wikipedia.org\/wiki\/Pipeline_\\(Unix\\) \"Pipeline (Unix)\") of multiple commands. For example, the following command line selects lines containing the text \"title\", sorts them alphabetically, and displays the result in a [terminal pager](https:\/\/en.wikipedia.org\/wiki\/Terminal_pager \"Terminal pager\"): `grep title somefile.txt | sort | less`. This creates at least three processes: one for [`grep`](https:\/\/en.wikipedia.org\/wiki\/Grep \"Grep\"), one for `sort`, and one for [`less`](https:\/\/en.wikipedia.org\/wiki\/Less_\\(Unix\\) \"Less (Unix)\"). Job control allows the shell to control these processes as one entity.\n\nA job is identified by a numeric *job ID*, a.k.a. *job number* which is classified as a [handle](https:\/\/en.wikipedia.org\/wiki\/Handle_\\(computing\\) \"Handle (computing)\") since it is an abstract reference to a [resource](https:\/\/en.wikipedia.org\/wiki\/System_resource \"System resource\") (a process group). An ID value, prefixed with `%`, can be used with a job control command to specify a job. The special references `%%` and `%+` refer to the default job, the one that would be selected if none were specified.[\\[3\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-3) Bash documentation refers to a reference (starting with `%`) as a *jobspec* (short for job specification).[\\[4\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-4)\n\nJob control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script.\n\n## Foreground\/background\n\\[[edit](https:\/\/en.wikipedia.org\/w\/index.php?title=Job_control_\\(Unix\\)&action=edit&section=3 \"Edit section: Foreground\/background\")\\]\n\nBy default, a job runs in the foreground where it uses [interactive input and output](https:\/\/en.wikipedia.org\/wiki\/Standard_streams \"Standard streams\"). The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may [redirect](https:\/\/en.wikipedia.org\/wiki\/Redirection_\\(computing\\) \"Redirection (computing)\") output for a background job to prevent this.\n\n[POSIX](https:\/\/en.wikipedia.org\/wiki\/POSIX \"POSIX\") specifies the [user interface](https:\/\/en.wikipedia.org\/wiki\/User_interface \"User interface\") to job control – modeled on the Korn shell.[\\[5\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-5) The commands are typically implemented as [shell builtins](https:\/\/en.wikipedia.org\/wiki\/Shell_builtin \"Shell builtin\"), not separate [programs](https:\/\/en.wikipedia.org\/wiki\/Computer_program \"Computer program\").\n\nStart in background\n\nIf a command line ends with `&`, then the job starts in the background.\n\nPause foreground job\n\nThe foreground job can be paused by pressing `Ctrl`\\+` Z`. In this state, a job can be resumed in the background via `bg` or resumed in the foreground via `fg`.\n\nCommand `fg`\n\nCommand `fg` (short for **f**ore**g**round) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via `Ctrl`\\+` Z`), then this command resumes that job.\n\nCommand `wait`\n\nCommand [`wait`](https:\/\/en.wikipedia.org\/wiki\/Wait_\\(command\\) \"Wait (command)\") pauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified.[\\[6\\]](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_note-6)\n\nCommand `bg`\n\nCommand `bg` (short for **b**ack**g**round) moves the paused foreground job to the background and resumes it.\n\nCommand `jobs`\n\nCommand `jobs` reports information about each background job including ID, command line and running status (stopped or running).\n\nThe [interprocess communication](https:\/\/en.wikipedia.org\/wiki\/Interprocess_communication \"Interprocess communication\") of job control is implemented via [signals](https:\/\/en.wikipedia.org\/wiki\/Signal_\\(IPC\\) \"Signal (IPC)\").\n\nTypically, a shell maintains information about background jobs in a job table. When an [interactive session](https:\/\/en.wikipedia.org\/wiki\/Login_session \"Login session\") ends (i.e. user [logs out](https:\/\/en.wikipedia.org\/wiki\/Logout \"Logout\")), the shell sends signal [SIGHUP](https:\/\/en.wikipedia.org\/wiki\/SIGHUP \"SIGHUP\") to all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command [`disown`](https:\/\/en.wikipedia.org\/wiki\/Disown_\\(Unix\\) \"Disown (Unix)\") that removes a job from the job table. The process group becomes an [orphan](https:\/\/en.wikipedia.org\/wiki\/Orphan_process \"Orphan process\"). The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a [daemon](https:\/\/en.wikipedia.org\/wiki\/Daemon_\\(computing\\) \"Daemon (computing)\") owned directly by the root process [init](https:\/\/en.wikipedia.org\/wiki\/Init \"Init\"). The POSIX command [`nohup`](https:\/\/en.wikipedia.org\/wiki\/Nohup \"Nohup\") provides an alternate way to prevent a job from being terminated by the shell.\n\nSuspending the foreground job (via `Ctrl`\\+`Z`) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored.\n\nWhen the user presses `Ctrl`\\+`C`, the shell sends signal [SIGINT](https:\/\/en.wikipedia.org\/wiki\/SIGINT_\\(POSIX\\) \"SIGINT (POSIX)\") (interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal.\n\nWhen a stopped job is resumed (via `bg` or `fg`), the shell redirects [Input\/output](https:\/\/en.wikipedia.org\/wiki\/Input\/output \"Input\/output\") and resumes it by sending signal SIGCONT to it.\n\nA background process that attempts to read from or write to its [controlling terminal](https:\/\/en.wikipedia.org\/wiki\/Controlling_terminal \"Controlling terminal\") is sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default.\n\nIn bash, the `kill` builtin (not `\/bin\/kill`) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group. `kill` can send any signal to a job; however, if the intent is to rid the system of the processes, the signals [SIGKILL](https:\/\/en.wikipedia.org\/wiki\/SIGKILL \"SIGKILL\") and [SIGTERM](https:\/\/en.wikipedia.org\/wiki\/SIGTERM \"SIGTERM\") (the default) are probably the most applicable.\n\n1. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-1)** IEEE Std 1003.1-2001, [Section 3.201, Job](http:\/\/pubs.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_201) [Archived](https:\/\/web.archive.org\/web\/20190801165956\/http:\/\/pubs.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_201) 2019-08-01 at the [Wayback Machine](https:\/\/en.wikipedia.org\/wiki\/Wayback_Machine \"Wayback Machine\")\n2. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-2)**\n   Foreword by [Bill Joy](https:\/\/en.wikipedia.org\/wiki\/Bill_Joy \"Bill Joy\") in\n   \n   Anderson, Gail; Paul Anderson (1986). [*The UNIX C Shell Field Guide*](https:\/\/archive.org\/details\/unixcshellfieldg00ande). Prentice-Hall. p. xvii. [ISBN](https:\/\/en.wikipedia.org\/wiki\/ISBN_\\(identifier\\) \"ISBN (identifier)\")\n   \n   [0-13-937468-X](https:\/\/en.wikipedia.org\/wiki\/Special:BookSources\/0-13-937468-X \"Special:BookSources\/0-13-937468-X\")\n   \n   .\n3. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-3)** IEEE Std 1003.1-2001, [Section 3.203, Job Control Job ID](http:\/\/www.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_203) [Archived](https:\/\/web.archive.org\/web\/20101009060625\/http:\/\/www.opengroup.org\/onlinepubs\/009695399\/basedefs\/xbd_chap03.html#tag_03_203) 2010-10-09 at the [Wayback Machine](https:\/\/en.wikipedia.org\/wiki\/Wayback_Machine \"Wayback Machine\")\n4. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-4)**\n   [\"7.1 Job Control Basics\"](https:\/\/www.gnu.org\/software\/bash\/manual\/html_node\/Job-Control-Basics.html#Job-Control-Basics). [Archived](https:\/\/web.archive.org\/web\/20160802215912\/http:\/\/www.gnu.org\/software\/bash\/manual\/html_node\/Job-Control-Basics.html#Job-Control-Basics) from the original on 2016-08-02. Retrieved 2016-07-22.\n5. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-5)** `bg` – Shell and Utilities Reference, [The Single UNIX Specification](https:\/\/en.wikipedia.org\/wiki\/Single_Unix_Specification \"Single Unix Specification\"), Version 5 from [The Open Group](https:\/\/en.wikipedia.org\/wiki\/The_Open_Group \"The Open Group\"); `fg` – Shell and Utilities Reference, [The Single UNIX Specification](https:\/\/en.wikipedia.org\/wiki\/Single_Unix_Specification \"Single Unix Specification\"), Version 5 from [The Open Group](https:\/\/en.wikipedia.org\/wiki\/The_Open_Group \"The Open Group\").\n6. **[^](https:\/\/en.wikipedia.org\/wiki\/Job_control_\\(Unix\\)#cite_ref-6)**\n   Kerrisk, Michael (Feb 2, 2025). [\"wait(1p) — Linux manual page\"](https:\/\/www.man7.org\/linux\/man-pages\/man1\/wait.1p.html). *man7.org*. [Archived](https:\/\/web.archive.org\/web\/20250516160332\/https:\/\/www.man7.org\/linux\/man-pages\/man1\/wait.1p.html) from the original on May 16, 2025. Retrieved May 13, 2025.\n\n- [Marshall Kirk McKusick](https:\/\/en.wikipedia.org\/wiki\/Marshall_Kirk_McKusick \"Marshall Kirk McKusick\") and George V. Neville-Neil (2004-08-02). [\"FreeBSD Process Management: Process Groups and Sessions\"](http:\/\/www.informit.com\/articles\/article.aspx?p=366888&seqNum=8). [*The Design and Implementation of the FreeBSD Operating System*](http:\/\/www.informit.com\/title\/0201702452). Addison Wesley. [ISBN](https:\/\/en.wikipedia.org\/wiki\/ISBN_\\(identifier\\) \"ISBN (identifier)\")\n  \n  [0-201-70245-2](https:\/\/en.wikipedia.org\/wiki\/Special:BookSources\/0-201-70245-2 \"Special:BookSources\/0-201-70245-2\")\n  \n  .\n\n- \"Job Control\", [*Bash Reference Manual*](https:\/\/web.archive.org\/web\/20060523213233\/http:\/\/cnswww.cns.cwru.edu\/~chet\/bash\/bashref.html)","meta_canonical":null}

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Boilerpipe Text	From Wikipedia, the free encyclopedia This article is about job control on a Unix-based system. For the general computing term, see job control . In a Unix or Unix-like operating system , job control refers to controlling a process group as a job via a shell . [ 1 ] Control features include suspend, resume, and terminate, and more advanced features can be performed by sending a signal to a job. Job control allows a user to manage processing in the Unix-based multiprocessing environment, and is distinct from general computing job control . Job control was first implemented in the C shell by Jim Kulp, [ 2 ] then at IIASA in Austria, making use of features of the 4.1 BSD kernel. The KornShell , developed at Bell Labs , adopted it and it was later incorporated into the SVR4 version of the Bourne shell , and exists in most modern Unix shells. A job encompasses all of the processes that start for the handling of a shell command line . A simple command line may start just one process, but a command line may result in multiple processes since a process can create child processes , and a command line can specify a pipeline of multiple commands. For example, the following command line selects lines containing the text "title", sorts them alphabetically, and displays the result in a terminal pager : grep title somefile.txt \| sort \| less . This creates at least three processes: one for grep , one for sort , and one for less . Job control allows the shell to control these processes as one entity. A job is identified by a numeric job ID , a.k.a. job number which is classified as a handle since it is an abstract reference to a resource (a process group). An ID value, prefixed with % , can be used with a job control command to specify a job. The special references %% and %+ refer to the default job, the one that would be selected if none were specified. [ 3 ] Bash documentation refers to a reference (starting with % ) as a jobspec (short for job specification). [ 4 ] Job control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script. Foreground/background [ edit ] By default, a job runs in the foreground where it uses interactive input and output . The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may redirect output for a background job to prevent this. POSIX specifies the user interface to job control – modeled on the Korn shell. [ 5 ] The commands are typically implemented as shell builtins , not separate programs . Start in background If a command line ends with & , then the job starts in the background. Pause foreground job The foreground job can be paused by pressing Ctrl + Z . In this state, a job can be resumed in the background via bg or resumed in the foreground via fg . Command fg Command fg (short for f ore g round) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via Ctrl + Z ), then this command resumes that job. Command wait Command wait pauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified. [ 6 ] Command bg Command bg (short for b ack g round) moves the paused foreground job to the background and resumes it. Command jobs Command jobs reports information about each background job including ID, command line and running status (stopped or running). The interprocess communication of job control is implemented via signals . Typically, a shell maintains information about background jobs in a job table. When an interactive session ends (i.e. user logs out ), the shell sends signal SIGHUP to all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command disown that removes a job from the job table. The process group becomes an orphan . The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a daemon owned directly by the root process init . The POSIX command nohup provides an alternate way to prevent a job from being terminated by the shell. Suspending the foreground job (via Ctrl + Z ) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored. When the user presses Ctrl + C , the shell sends signal SIGINT (interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal. When a stopped job is resumed (via bg or fg ), the shell redirects Input/output and resumes it by sending signal SIGCONT to it. A background process that attempts to read from or write to its controlling terminal is sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default. In bash, the kill builtin (not /bin/kill ) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group. kill can send any signal to a job; however, if the intent is to rid the system of the processes, the signals SIGKILL and SIGTERM (the default) are probably the most applicable. ^ IEEE Std 1003.1-2001, Section 3.201, Job Archived 2019-08-01 at the Wayback Machine ^ Foreword by Bill Joy in Anderson, Gail; Paul Anderson (1986). The UNIX C Shell Field Guide . Prentice-Hall. p. xvii. ISBN 0-13-937468-X . ^ IEEE Std 1003.1-2001, Section 3.203, Job Control Job ID Archived 2010-10-09 at the Wayback Machine ^ "7.1 Job Control Basics" . Archived from the original on 2016-08-02 . Retrieved 2016-07-22 . ^ bg – Shell and Utilities Reference, The Single UNIX Specification , Version 5 from The Open Group ; fg – Shell and Utilities Reference, The Single UNIX Specification , Version 5 from The Open Group . ^ Kerrisk, Michael (Feb 2, 2025). "wait(1p) — Linux manual page" . man7.org . Archived from the original on May 16, 2025 . Retrieved May 13, 2025 . Marshall Kirk McKusick and George V. Neville-Neil (2004-08-02). "FreeBSD Process Management: Process Groups and Sessions" . The Design and Implementation of the FreeBSD Operating System . Addison Wesley. ISBN 0-201-70245-2 . "Job Control", Bash Reference Manual
Markdown	[Jump to content](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#bodyContent) Main menu Main menu move to sidebar hide Navigation - [Main page](https://en.wikipedia.org/wiki/Main_Page "Visit the main page [z]") - [Contents](https://en.wikipedia.org/wiki/Wikipedia:Contents "Guides to browsing Wikipedia") - [Current events](https://en.wikipedia.org/wiki/Portal:Current_events "Articles related to current events") - [Random article](https://en.wikipedia.org/wiki/Special:Random "Visit a randomly selected article [x]") - [About Wikipedia](https://en.wikipedia.org/wiki/Wikipedia:About "Learn about Wikipedia and how it works") - [Contact us](https://en.wikipedia.org/wiki/Wikipedia:Contact_us "How to contact Wikipedia") Contribute - [Help](https://en.wikipedia.org/wiki/Help:Contents "Guidance on how to use and edit Wikipedia") - [Learn to edit](https://en.wikipedia.org/wiki/Help:Introduction "Learn how to edit Wikipedia") - [Community portal](https://en.wikipedia.org/wiki/Wikipedia:Community_portal "The hub for editors") - [Recent changes](https://en.wikipedia.org/wiki/Special:RecentChanges "A list of recent changes to Wikipedia [r]") - [Upload file](https://en.wikipedia.org/wiki/Wikipedia:File_upload_wizard "Add images or other media for use on Wikipedia") - [Special pages](https://en.wikipedia.org/wiki/Special:SpecialPages "A list of all special pages [q]") [![](https://en.wikipedia.org/static/images/icons/enwiki-25.svg) ![Wikipedia](https://en.wikipedia.org/static/images/mobile/copyright/wikipedia-wordmark-en-25.svg) ![The Free Encyclopedia](https://en.wikipedia.org/static/images/mobile/copyright/wikipedia-tagline-en-25.svg)](https://en.wikipedia.org/wiki/Main_Page) [Search](https://en.wikipedia.org/wiki/Special:Search "Search Wikipedia [f]") Appearance - [Donate](https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en) - [Create account](https://en.wikipedia.org/w/index.php?title=Special:CreateAccount&returnto=Job+control+%28Unix%29 "You are encouraged to create an account and log in; however, it is not mandatory") - [Log in](https://en.wikipedia.org/w/index.php?title=Special:UserLogin&returnto=Job+control+%28Unix%29 "You're encouraged to log in; however, it's not mandatory. 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[o]") ## Contents move to sidebar hide - [(Top)](https://en.wikipedia.org/wiki/Job_control_\(Unix\)) - [1 Job](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Job) - [2 Job ID](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Job_ID) - [3 Foreground/background](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Foreground/background) - [4 Control](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Control) - [5 Signals](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Signals) - [6 References](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#References) - [7 Further reading](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#Further_reading) - [8 External links](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#External_links) Toggle the table of contents # Job control (Unix) 7 languages - [Català](https://ca.wikipedia.org/wiki/Control_de_tasques_\(Unix\) "Control de tasques (Unix) – Catalan") - [Čeština](https://cs.wikipedia.org/wiki/%C5%98%C3%ADzen%C3%AD_%C3%BAloh_\(Unix\) "Řízení úloh (Unix) – Czech") - [Deutsch](https://de.wikipedia.org/wiki/Job_control "Job control – German") - [Français](https://fr.wikipedia.org/wiki/SIGTSTP "SIGTSTP – French") - [한국어](https://ko.wikipedia.org/wiki/Jobs_\(%EC%9C%A0%EB%8B%89%EC%8A%A4\) "Jobs (유닉스) – Korean") - [Português](https://pt.wikipedia.org/wiki/Controle_de_trabalhos_\(Unix\) "Controle de trabalhos (Unix) – Portuguese") - [Русский](https://ru.wikipedia.org/wiki/%D0%A3%D0%BF%D1%80%D0%B0%D0%B2%D0%BB%D0%B5%D0%BD%D0%B8%D0%B5_%D0%B7%D0%B0%D0%B4%D0%B0%D0%BD%D0%B8%D1%8F%D0%BC%D0%B8 "Управление заданиями – Russian") [Edit links](https://www.wikidata.org/wiki/Special:EntityPage/Q6206712#sitelinks-wikipedia "Edit interlanguage links") - [Article](https://en.wikipedia.org/wiki/Job_control_\(Unix\) "View the content page [c]") - [Talk](https://en.wikipedia.org/wiki/Talk:Job_control_\(Unix\) "Discuss improvements to the content page [t]") English - [Read](https://en.wikipedia.org/wiki/Job_control_\(Unix\)) - [Edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit "Edit this page [e]") - [View history](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=history "Past revisions of this page [h]") Tools Tools move to sidebar hide Actions - [Read](https://en.wikipedia.org/wiki/Job_control_\(Unix\)) - [Edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit "Edit this page [e]") - [View history](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=history) General - [What links here](https://en.wikipedia.org/wiki/Special:WhatLinksHere/Job_control_\(Unix\) "List of all English Wikipedia pages containing links to this page [j]") - [Related changes](https://en.wikipedia.org/wiki/Special:RecentChangesLinked/Job_control_\(Unix\) "Recent changes in pages linked from this page [k]") - [Upload file](https://en.wikipedia.org/wiki/Wikipedia:File_Upload_Wizard "Upload files [u]") - [Permanent link](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&oldid=1336330596 "Permanent link to this revision of this page") - [Page information](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=info "More information about this page") - [Cite this page](https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Job_control_%28Unix%29&id=1336330596&wpFormIdentifier=titleform "Information on how to cite this page") - [Get shortened URL](https://en.wikipedia.org/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FJob_control_%28Unix%29) Print/export - [Download as PDF](https://en.wikipedia.org/w/index.php?title=Special:DownloadAsPdf&page=Job_control_%28Unix%29&action=show-download-screen "Download this page as a PDF file") - [Printable version](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&printable=yes "Printable version of this page [p]") In other projects - [Wikidata item](https://www.wikidata.org/wiki/Special:EntityPage/Q6206712 "Structured data on this page hosted by Wikidata [g]") Appearance move to sidebar hide From Wikipedia, the free encyclopedia Control of jobs in a Unix shell This article is about job control on a Unix-based system. For the general computing term, see [job control](https://en.wikipedia.org/wiki/Job_control_\(computing\) "Job control (computing)"). In a [Unix](https://en.wikipedia.org/wiki/Unix "Unix") or [Unix-like](https://en.wikipedia.org/wiki/Unix-like "Unix-like") [operating system](https://en.wikipedia.org/wiki/Operating_system "Operating system"), job control refers to controlling a [process group](https://en.wikipedia.org/wiki/Process_group "Process group") as a [job](https://en.wikipedia.org/wiki/Job_\(computing\) "Job (computing)") via a [shell](https://en.wikipedia.org/wiki/Unix_shell "Unix shell").[\[1\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-1) Control features include suspend, resume, and terminate, and more advanced features can be performed by sending a [signal](https://en.wikipedia.org/wiki/Signal_\(IPC\) "Signal (IPC)") to a job. Job control allows a user to manage processing in the Unix-based [multiprocessing](https://en.wikipedia.org/wiki/Multiprocessing "Multiprocessing") environment, and is distinct from [general computing job control](https://en.wikipedia.org/wiki/Job_control_\(computing\) "Job control (computing)"). Job control was first implemented in the [C shell](https://en.wikipedia.org/wiki/C_shell "C shell") by Jim Kulp,[\[2\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-2) then at [IIASA](https://en.wikipedia.org/wiki/IIASA "IIASA") in Austria, making use of features of the 4.1[BSD](https://en.wikipedia.org/wiki/BSD "BSD") kernel. The [KornShell](https://en.wikipedia.org/wiki/KornShell "KornShell"), developed at [Bell Labs](https://en.wikipedia.org/wiki/Bell_Labs "Bell Labs"), adopted it and it was later incorporated into the SVR4 version of the [Bourne shell](https://en.wikipedia.org/wiki/Bourne_shell "Bourne shell"), and exists in most modern Unix shells. ## Job \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=1 "Edit section: Job")\] A job encompasses all of the processes that start for the handling of a shell [command line](https://en.wikipedia.org/wiki/Command-line_interface "Command-line interface"). A simple command line may start just one process, but a command line may result in multiple processes since a process can create [child processes](https://en.wikipedia.org/wiki/Child_process "Child process"), and a command line can specify a [pipeline](https://en.wikipedia.org/wiki/Pipeline_\(Unix\) "Pipeline (Unix)") of multiple commands. For example, the following command line selects lines containing the text "title", sorts them alphabetically, and displays the result in a [terminal pager](https://en.wikipedia.org/wiki/Terminal_pager "Terminal pager"): `grep title somefile.txt \| sort \| less`. This creates at least three processes: one for [`grep`](https://en.wikipedia.org/wiki/Grep "Grep"), one for `sort`, and one for [`less`](https://en.wikipedia.org/wiki/Less_\(Unix\) "Less (Unix)"). Job control allows the shell to control these processes as one entity. ## Job ID \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=2 "Edit section: Job ID")\] A job is identified by a numeric job ID, a.k.a. job number which is classified as a [handle](https://en.wikipedia.org/wiki/Handle_\(computing\) "Handle (computing)") since it is an abstract reference to a [resource](https://en.wikipedia.org/wiki/System_resource "System resource") (a process group). An ID value, prefixed with `%`, can be used with a job control command to specify a job. The special references `%%` and `%+` refer to the default job, the one that would be selected if none were specified.[\[3\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-3) Bash documentation refers to a reference (starting with `%`) as a jobspec (short for job specification).[\[4\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-4) Job control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script. ## Foreground/background \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=3 "Edit section: Foreground/background")\] By default, a job runs in the foreground where it uses [interactive input and output](https://en.wikipedia.org/wiki/Standard_streams "Standard streams"). The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may [redirect](https://en.wikipedia.org/wiki/Redirection_\(computing\) "Redirection (computing)") output for a background job to prevent this. ## Control \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=4 "Edit section: Control")\] [POSIX](https://en.wikipedia.org/wiki/POSIX "POSIX") specifies the [user interface](https://en.wikipedia.org/wiki/User_interface "User interface") to job control – modeled on the Korn shell.[\[5\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-5) The commands are typically implemented as [shell builtins](https://en.wikipedia.org/wiki/Shell_builtin "Shell builtin"), not separate [programs](https://en.wikipedia.org/wiki/Computer_program "Computer program"). Start in background If a command line ends with `&`, then the job starts in the background. Pause foreground job The foreground job can be paused by pressing `Ctrl`\+` Z`. In this state, a job can be resumed in the background via `bg` or resumed in the foreground via `fg`. Command `fg` Command `fg` (short for foreground) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via `Ctrl`\+` Z`), then this command resumes that job. Command `wait` Command [`wait`](https://en.wikipedia.org/wiki/Wait_\(command\) "Wait (command)") pauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified.[\[6\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-6) Command `bg` Command `bg` (short for background) moves the paused foreground job to the background and resumes it. Command `jobs` Command `jobs` reports information about each background job including ID, command line and running status (stopped or running). ## Signals \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=5 "Edit section: Signals")\] \| \| \| \|---\|---\| \| [![icon](https://upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/60px-Question_book-new.svg.png)](https://en.wikipedia.org/wiki/File:Question_book-new.svg) \| This section does not [cite](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources "Wikipedia:Citing sources") any [sources](https://en.wikipedia.org/wiki/Wikipedia:Verifiability "Wikipedia:Verifiability"). Please help [improve this section](https://en.wikipedia.org/wiki/Special:EditPage/Job_control_\(Unix\) "Special:EditPage/Job control (Unix)") by [adding citations to reliable sources](https://en.wikipedia.org/wiki/Help:Referencing_for_beginners "Help:Referencing for beginners"). Unsourced material may be challenged and [removed](https://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence "Wikipedia:Verifiability"). (February 2020) ([Learn how and when to remove this message](https://en.wikipedia.org/wiki/Help:Maintenance_template_removal "Help:Maintenance template removal")) \| The [interprocess communication](https://en.wikipedia.org/wiki/Interprocess_communication "Interprocess communication") of job control is implemented via [signals](https://en.wikipedia.org/wiki/Signal_\(IPC\) "Signal (IPC)"). Typically, a shell maintains information about background jobs in a job table. When an [interactive session](https://en.wikipedia.org/wiki/Login_session "Login session") ends (i.e. user [logs out](https://en.wikipedia.org/wiki/Logout "Logout")), the shell sends signal [SIGHUP](https://en.wikipedia.org/wiki/SIGHUP "SIGHUP") to all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command [`disown`](https://en.wikipedia.org/wiki/Disown_\(Unix\) "Disown (Unix)") that removes a job from the job table. The process group becomes an [orphan](https://en.wikipedia.org/wiki/Orphan_process "Orphan process"). The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a [daemon](https://en.wikipedia.org/wiki/Daemon_\(computing\) "Daemon (computing)") owned directly by the root process [init](https://en.wikipedia.org/wiki/Init "Init"). The POSIX command [`nohup`](https://en.wikipedia.org/wiki/Nohup "Nohup") provides an alternate way to prevent a job from being terminated by the shell. Suspending the foreground job (via `Ctrl`\+`Z`) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored. When the user presses `Ctrl`\+`C`, the shell sends signal [SIGINT](https://en.wikipedia.org/wiki/SIGINT_\(POSIX\) "SIGINT (POSIX)") (interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal. When a stopped job is resumed (via `bg` or `fg`), the shell redirects [Input/output](https://en.wikipedia.org/wiki/Input/output "Input/output") and resumes it by sending signal SIGCONT to it. A background process that attempts to read from or write to its [controlling terminal](https://en.wikipedia.org/wiki/Controlling_terminal "Controlling terminal") is sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default. In bash, the `kill` builtin (not `/bin/kill`) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group. `kill` can send any signal to a job; however, if the intent is to rid the system of the processes, the signals [SIGKILL](https://en.wikipedia.org/wiki/SIGKILL "SIGKILL") and [SIGTERM](https://en.wikipedia.org/wiki/SIGTERM "SIGTERM") (the default) are probably the most applicable. ## References \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=6 "Edit section: References")\] 1. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-1) IEEE Std 1003.1-2001, [Section 3.201, Job](http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_201) [Archived](https://web.archive.org/web/20190801165956/http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_201) 2019-08-01 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") 2. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-2) Foreword by [Bill Joy](https://en.wikipedia.org/wiki/Bill_Joy "Bill Joy") in Anderson, Gail; Paul Anderson (1986). [The UNIX C Shell Field Guide](https://archive.org/details/unixcshellfieldg00ande). Prentice-Hall. p. xvii. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-13-937468-X](https://en.wikipedia.org/wiki/Special:BookSources/0-13-937468-X "Special:BookSources/0-13-937468-X") . 3. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-3) IEEE Std 1003.1-2001, [Section 3.203, Job Control Job ID](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_203) [Archived](https://web.archive.org/web/20101009060625/http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_203) 2010-10-09 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") 4. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-4) ["7.1 Job Control Basics"](https://www.gnu.org/software/bash/manual/html_node/Job-Control-Basics.html#Job-Control-Basics). [Archived](https://web.archive.org/web/20160802215912/http://www.gnu.org/software/bash/manual/html_node/Job-Control-Basics.html#Job-Control-Basics) from the original on 2016-08-02. Retrieved 2016-07-22. 5. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-5) `bg` – Shell and Utilities Reference, [The Single UNIX Specification](https://en.wikipedia.org/wiki/Single_Unix_Specification "Single Unix Specification"), Version 5 from [The Open Group](https://en.wikipedia.org/wiki/The_Open_Group "The Open Group"); `fg` – Shell and Utilities Reference, [The Single UNIX Specification](https://en.wikipedia.org/wiki/Single_Unix_Specification "Single Unix Specification"), Version 5 from [The Open Group](https://en.wikipedia.org/wiki/The_Open_Group "The Open Group"). 6. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-6) Kerrisk, Michael (Feb 2, 2025). ["wait(1p) — Linux manual page"](https://www.man7.org/linux/man-pages/man1/wait.1p.html). man7.org. [Archived](https://web.archive.org/web/20250516160332/https://www.man7.org/linux/man-pages/man1/wait.1p.html) from the original on May 16, 2025. Retrieved May 13, 2025. ## Further reading \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=7 "Edit section: Further reading")\] - [Marshall Kirk McKusick](https://en.wikipedia.org/wiki/Marshall_Kirk_McKusick "Marshall Kirk McKusick") and George V. Neville-Neil (2004-08-02). ["FreeBSD Process Management: Process Groups and Sessions"](http://www.informit.com/articles/article.aspx?p=366888&seqNum=8). [The Design and Implementation of the FreeBSD Operating System](http://www.informit.com/title/0201702452). Addison Wesley. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-201-70245-2](https://en.wikipedia.org/wiki/Special:BookSources/0-201-70245-2 "Special:BookSources/0-201-70245-2") . ## External links \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=8 "Edit section: External links")\] - "Job Control", [Bash Reference Manual](https://web.archive.org/web/20060523213233/http://cnswww.cns.cwru.edu/~chet/bash/bashref.html) ![](https://en.wikipedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=1) Retrieved from "<https://en.wikipedia.org/w/index.php?title=Job_control_(Unix)&oldid=1336330596>" [Category](https://en.wikipedia.org/wiki/Help:Category "Help:Category"): - [Unix](https://en.wikipedia.org/wiki/Category:Unix "Category:Unix") Hidden categories: - [Webarchive template wayback links](https://en.wikipedia.org/wiki/Category:Webarchive_template_wayback_links "Category:Webarchive template wayback links") - [Articles with short description](https://en.wikipedia.org/wiki/Category:Articles_with_short_description "Category:Articles with short description") - [Short description is different from Wikidata](https://en.wikipedia.org/wiki/Category:Short_description_is_different_from_Wikidata "Category:Short description is different from Wikidata") - [Articles needing additional references from February 2020](https://en.wikipedia.org/wiki/Category:Articles_needing_additional_references_from_February_2020 "Category:Articles needing additional references from February 2020") - [All articles needing additional references](https://en.wikipedia.org/wiki/Category:All_articles_needing_additional_references "Category:All articles needing additional references") - This page was last edited on 3 February 2026, at 04:48 (UTC). - Text is available under the [Creative Commons Attribution-ShareAlike 4.0 License](https://en.wikipedia.org/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License "Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License"); additional terms may apply. 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Readable Markdown	From Wikipedia, the free encyclopedia This article is about job control on a Unix-based system. For the general computing term, see [job control](https://en.wikipedia.org/wiki/Job_control_\(computing\) "Job control (computing)"). In a [Unix](https://en.wikipedia.org/wiki/Unix "Unix") or [Unix-like](https://en.wikipedia.org/wiki/Unix-like "Unix-like") [operating system](https://en.wikipedia.org/wiki/Operating_system "Operating system"), job control refers to controlling a [process group](https://en.wikipedia.org/wiki/Process_group "Process group") as a [job](https://en.wikipedia.org/wiki/Job_\(computing\) "Job (computing)") via a [shell](https://en.wikipedia.org/wiki/Unix_shell "Unix shell").[\[1\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-1) Control features include suspend, resume, and terminate, and more advanced features can be performed by sending a [signal](https://en.wikipedia.org/wiki/Signal_\(IPC\) "Signal (IPC)") to a job. Job control allows a user to manage processing in the Unix-based [multiprocessing](https://en.wikipedia.org/wiki/Multiprocessing "Multiprocessing") environment, and is distinct from [general computing job control](https://en.wikipedia.org/wiki/Job_control_\(computing\) "Job control (computing)"). Job control was first implemented in the [C shell](https://en.wikipedia.org/wiki/C_shell "C shell") by Jim Kulp,[\[2\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-2) then at [IIASA](https://en.wikipedia.org/wiki/IIASA "IIASA") in Austria, making use of features of the 4.1[BSD](https://en.wikipedia.org/wiki/BSD "BSD") kernel. The [KornShell](https://en.wikipedia.org/wiki/KornShell "KornShell"), developed at [Bell Labs](https://en.wikipedia.org/wiki/Bell_Labs "Bell Labs"), adopted it and it was later incorporated into the SVR4 version of the [Bourne shell](https://en.wikipedia.org/wiki/Bourne_shell "Bourne shell"), and exists in most modern Unix shells. A job encompasses all of the processes that start for the handling of a shell [command line](https://en.wikipedia.org/wiki/Command-line_interface "Command-line interface"). A simple command line may start just one process, but a command line may result in multiple processes since a process can create [child processes](https://en.wikipedia.org/wiki/Child_process "Child process"), and a command line can specify a [pipeline](https://en.wikipedia.org/wiki/Pipeline_\(Unix\) "Pipeline (Unix)") of multiple commands. For example, the following command line selects lines containing the text "title", sorts them alphabetically, and displays the result in a [terminal pager](https://en.wikipedia.org/wiki/Terminal_pager "Terminal pager"): `grep title somefile.txt \| sort \| less`. This creates at least three processes: one for [`grep`](https://en.wikipedia.org/wiki/Grep "Grep"), one for `sort`, and one for [`less`](https://en.wikipedia.org/wiki/Less_\(Unix\) "Less (Unix)"). Job control allows the shell to control these processes as one entity. A job is identified by a numeric job ID, a.k.a. job number which is classified as a [handle](https://en.wikipedia.org/wiki/Handle_\(computing\) "Handle (computing)") since it is an abstract reference to a [resource](https://en.wikipedia.org/wiki/System_resource "System resource") (a process group). An ID value, prefixed with `%`, can be used with a job control command to specify a job. The special references `%%` and `%+` refer to the default job, the one that would be selected if none were specified.[\[3\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-3) Bash documentation refers to a reference (starting with `%`) as a jobspec (short for job specification).[\[4\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-4) Job control ID values are typically only used in an interactive shell. In scripting, PGID values are used instead, as they are more precise and robust, and indeed job control is disabled by default in a bash script. ## Foreground/background \[[edit](https://en.wikipedia.org/w/index.php?title=Job_control_\(Unix\)&action=edit&section=3 "Edit section: Foreground/background")\] By default, a job runs in the foreground where it uses [interactive input and output](https://en.wikipedia.org/wiki/Standard_streams "Standard streams"). The user enters a command line and interacts with the processes but cannot issue another command until the current job terminates. Many operations (i.e. listing files) are relatively quick so the user can wait for a response with little down time and some operations (i.e. editing) require interaction that is only possible via a foreground job. But, if interaction is not required and the operation prevents access to the shell for a long time, the user may want to run it in the background – where the processes cannot access interactive input but the user can perform other foreground operations while the background job runs concurrently. By default background jobs output to the interactive output stream which results in the interleaving of output from the foreground and background jobs although a user may [redirect](https://en.wikipedia.org/wiki/Redirection_\(computing\) "Redirection (computing)") output for a background job to prevent this. [POSIX](https://en.wikipedia.org/wiki/POSIX "POSIX") specifies the [user interface](https://en.wikipedia.org/wiki/User_interface "User interface") to job control – modeled on the Korn shell.[\[5\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-5) The commands are typically implemented as [shell builtins](https://en.wikipedia.org/wiki/Shell_builtin "Shell builtin"), not separate [programs](https://en.wikipedia.org/wiki/Computer_program "Computer program"). Start in background If a command line ends with `&`, then the job starts in the background. Pause foreground job The foreground job can be paused by pressing `Ctrl`\+` Z`. In this state, a job can be resumed in the background via `bg` or resumed in the foreground via `fg`. Command `fg` Command `fg` (short for foreground) moves background job to the foreground, either the job specified or the one most recently added to the background if none specified. When the foreground job is paused (via `Ctrl`\+` Z`), then this command resumes that job. Command `wait` Command [`wait`](https://en.wikipedia.org/wiki/Wait_\(command\) "Wait (command)") pauses the interactive session until the specified background jobs complete or for all background jobs of the active shell if none specified.[\[6\]](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_note-6) Command `bg` Command `bg` (short for background) moves the paused foreground job to the background and resumes it. Command `jobs` Command `jobs` reports information about each background job including ID, command line and running status (stopped or running). The [interprocess communication](https://en.wikipedia.org/wiki/Interprocess_communication "Interprocess communication") of job control is implemented via [signals](https://en.wikipedia.org/wiki/Signal_\(IPC\) "Signal (IPC)"). Typically, a shell maintains information about background jobs in a job table. When an [interactive session](https://en.wikipedia.org/wiki/Login_session "Login session") ends (i.e. user [logs out](https://en.wikipedia.org/wiki/Logout "Logout")), the shell sends signal [SIGHUP](https://en.wikipedia.org/wiki/SIGHUP "SIGHUP") to all jobs, and waits for the process groups to exit before terminating itself. Some shells provide a non-POSIX command [`disown`](https://en.wikipedia.org/wiki/Disown_\(Unix\) "Disown (Unix)") that removes a job from the job table. The process group becomes an [orphan](https://en.wikipedia.org/wiki/Orphan_process "Orphan process"). The shell will not send it SIGHUP, nor wait for it to terminate. This is one technique for enabling a process as a [daemon](https://en.wikipedia.org/wiki/Daemon_\(computing\) "Daemon (computing)") owned directly by the root process [init](https://en.wikipedia.org/wiki/Init "Init"). The POSIX command [`nohup`](https://en.wikipedia.org/wiki/Nohup "Nohup") provides an alternate way to prevent a job from being terminated by the shell. Suspending the foreground job (via `Ctrl`\+`Z`) sends signal SIGTSTP (terminal stop) to the processes of the group. By default, this signal causes a process to pause so that the shell can resume. However, a process can ignore the signal. A process can also be paused via signal SIGSTOP (stop), which cannot be ignored. When the user presses `Ctrl`\+`C`, the shell sends signal [SIGINT](https://en.wikipedia.org/wiki/SIGINT_\(POSIX\) "SIGINT (POSIX)") (interrupt) to each foreground job process, which defaults to terminating it, though a process can ignore the signal. When a stopped job is resumed (via `bg` or `fg`), the shell redirects [Input/output](https://en.wikipedia.org/wiki/Input/output "Input/output") and resumes it by sending signal SIGCONT to it. A background process that attempts to read from or write to its [controlling terminal](https://en.wikipedia.org/wiki/Controlling_terminal "Controlling terminal") is sent signal SIGTTIN (for input) or SIGTTOU (for output). These signals stop the process by default, but they may also be handled in other ways. Shells often override the default stop action of SIGTTOU so that background processes deliver their output to the controlling terminal by default. In bash, the `kill` builtin (not `/bin/kill`) can signal jobs by ID as well as by process group ID. Sending a signal to a job sends it to each process of the group. `kill` can send any signal to a job; however, if the intent is to rid the system of the processes, the signals [SIGKILL](https://en.wikipedia.org/wiki/SIGKILL "SIGKILL") and [SIGTERM](https://en.wikipedia.org/wiki/SIGTERM "SIGTERM") (the default) are probably the most applicable. 1. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-1) IEEE Std 1003.1-2001, [Section 3.201, Job](http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_201) [Archived](https://web.archive.org/web/20190801165956/http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_201) 2019-08-01 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") 2. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-2) Foreword by [Bill Joy](https://en.wikipedia.org/wiki/Bill_Joy "Bill Joy") in Anderson, Gail; Paul Anderson (1986). [The UNIX C Shell Field Guide](https://archive.org/details/unixcshellfieldg00ande). Prentice-Hall. p. xvii. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-13-937468-X](https://en.wikipedia.org/wiki/Special:BookSources/0-13-937468-X "Special:BookSources/0-13-937468-X") . 3. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-3) IEEE Std 1003.1-2001, [Section 3.203, Job Control Job ID](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_203) [Archived](https://web.archive.org/web/20101009060625/http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_203) 2010-10-09 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") 4. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-4) ["7.1 Job Control Basics"](https://www.gnu.org/software/bash/manual/html_node/Job-Control-Basics.html#Job-Control-Basics). [Archived](https://web.archive.org/web/20160802215912/http://www.gnu.org/software/bash/manual/html_node/Job-Control-Basics.html#Job-Control-Basics) from the original on 2016-08-02. Retrieved 2016-07-22. 5. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-5) `bg` – Shell and Utilities Reference, [The Single UNIX Specification](https://en.wikipedia.org/wiki/Single_Unix_Specification "Single Unix Specification"), Version 5 from [The Open Group](https://en.wikipedia.org/wiki/The_Open_Group "The Open Group"); `fg` – Shell and Utilities Reference, [The Single UNIX Specification](https://en.wikipedia.org/wiki/Single_Unix_Specification "Single Unix Specification"), Version 5 from [The Open Group](https://en.wikipedia.org/wiki/The_Open_Group "The Open Group"). 6. [^](https://en.wikipedia.org/wiki/Job_control_\(Unix\)#cite_ref-6) Kerrisk, Michael (Feb 2, 2025). ["wait(1p) — Linux manual page"](https://www.man7.org/linux/man-pages/man1/wait.1p.html). man7.org. [Archived](https://web.archive.org/web/20250516160332/https://www.man7.org/linux/man-pages/man1/wait.1p.html) from the original on May 16, 2025. Retrieved May 13, 2025. - [Marshall Kirk McKusick](https://en.wikipedia.org/wiki/Marshall_Kirk_McKusick "Marshall Kirk McKusick") and George V. Neville-Neil (2004-08-02). ["FreeBSD Process Management: Process Groups and Sessions"](http://www.informit.com/articles/article.aspx?p=366888&seqNum=8). [The Design and Implementation of the FreeBSD Operating System](http://www.informit.com/title/0201702452). Addison Wesley. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-201-70245-2](https://en.wikipedia.org/wiki/Special:BookSources/0-201-70245-2 "Special:BookSources/0-201-70245-2") . - "Job Control", [Bash Reference Manual](https://web.archive.org/web/20060523213233/http://cnswww.cns.cwru.edu/~chet/bash/bashref.html)
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