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Calculated Shard: 111 (from laksa118)

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curl -X POST \
  'http://laksa111.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://www.networkworld.com/article/3600146/how-to-loop-forever-in-bash.html\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.networkworld.com/article/3600146/how-to-loop-forever-in-bash.html\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.networkworld.com\/article\/3600146\/how-to-loop-forever-in-bash.html","crawl_time":1775274350,"first_indexed_time":1730920739,"http_code":200,"src_unparsed":"com,networkworld!www,\/article\/3600146\/how-to-loop-forever-in-bash.html s443","src_root_hash":"6029952698187917311","history_drop_reason":null,"meta_title":"How to loop forever in bash | Network World","meta_descriptions":["Looping forever is easy if you know what commands you want to run repeatedly and the conditions under which you want them to stop running."],"attrs_boilerpipe_text":"There are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this.\nThe\nfor\n and \nwhile\n commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques.\nUsing while\nOne of the easiest forever-loops involves using the \nwhile\n command followed by the condition “true”. You don’t have to bother with logic like while [ 1 -eq 1 ] or similar tests. The \nwhile true\n test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example:\n$ while true\n> do\n>   echo Keep running\n>   sleep 3\n> done\nKeep running\nKeep running\nKeep running\n^C\nThe command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once!\n$ while false\n> do\n>   echo Keep running\n>   sleep 3\n> done\n$\nYou can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it.\nwhile :\ndo\necho Keep running\nsleep 3\ndone\nIf you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below.\nwhile :\ndo\necho Keep running\necho \"Press CTRL+C to exit\"\nsleep 3\ndone\nYou can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below.\nwhile true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done\nThe command below would work the same. I prefer\nwhile true\nbecause it seems obvious, but any of the examples shown will work as does this one:\nwhile [ 1 ]\ndo\necho Keep running\necho \"Press CTRL+C to exit\"\nsleep 3\ndone\nUsing for\nThe \nfor\n command also provides an easy way to loop forever. While not quite as obvious as the\nwhile true\noption, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this:\n$ for (int i = 0; i < 5; i++)\nInstead, use the\nfor\ncommand with no such values as in the example below.\n$ for (( ; ; ))\n> do\n>    echo Keep your spirits up\n>    echo “Press CTRL+C to exit”\n>    sleep 3\n> done\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\nAnd, obviously, press CTRL-C when you want to exit the loop.\nWhy loop forever?\nOf course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the\ndate\ncommand with the\n+%H\noption to check the time, then reminds you that it’s time to go home and exits. The\nsleep 60\ncommand was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time.\n#!\/bin\/bash\nwhile true\ndo\nif [ `date +%H` -ge 17 ]; then\necho Time to go home\nexit\t# exit script\nelse\nsleep 60\nfi\ndone\nIf you want to exit the loop instead of exiting the script, you can use a\nbreak\ncommand\ninstead of an exit command as shown in the example below.\n#!\/bin\/bash\nwhile true\ndo\nif [ `date +%H` -ge 17 ]; then\nbreak\t# exit loop\nfi\necho Time to go home\ndone\nWrap-up\nLooping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use.\nMore Linux tips and how-tos:","attrs_markdown":"1. Topics\n2. [News](https:\/\/www.networkworld.com\/news\/)\n3. [Opinion](https:\/\/www.networkworld.com\/opinions\/)\n4. [Features](https:\/\/www.networkworld.com\/feature\/)\n5. 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AdChoices](https:\/\/foundryco.com\/ad-choices\/)\n- [Your California Privacy Rights](https:\/\/foundryco.com\/ccpa\/)\n\nBack\n\n## Our Network\n- [CIO](https:\/\/www.cio.com\/)\n- [Computerworld](https:\/\/www.computerworld.com\/)\n- [CSO](https:\/\/www.csoonline.com\/)\n- [InfoWorld](https:\/\/www.infoworld.com\/)\n\nBack\n\n## More\n- [News](https:\/\/www.networkworld.com\/news\/)\n- [Features](https:\/\/www.networkworld.com\/feature\/)\n- [Blogs\/Opinion](https:\/\/www.networkworld.com\/blogs\/)\n- [BrandPosts](https:\/\/www.networkworld.com\/brandposts\/)\n- [Events](https:\/\/www.networkworld.com\/events\/)\n- [Videos](https:\/\/www.networkworld.com\/videos\/)\n- [Buyer’s Guides](https:\/\/www.networkworld.com\/enterprise-buyers-guide\/)\n\n1. [Home](https:\/\/www.networkworld.com\/)\n2. [Blogs](https:\/\/www.networkworld.com\/blogs\/)\n3. [Unix as a Second Language](https:\/\/www.networkworld.com\/blogs\/unix-as-a-second-language\/)\n\n![sandra\\_henrystocker](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/06\/2004-0-39498900-1750715051-sandra_h-s-3-100646724-orig.jpg?quality=50&strip=all&w=113)\n\nby [Sandra Henry Stocker](https:\/\/www.networkworld.com\/profile\/sandra-henry-stocker\/)\n\nUnix Dweeb\n\n# How to loop forever in bash\nHow-To\n\nNov 6, 20245 mins\n\n## Looping forever is easy if you know what commands you want to run repeatedly and the conditions under which you want them to stop running.\n![upside down roller coaster in a loop against a cloud and blue sky amusement park](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/02\/3600146-0-40350400-1740688644-shutterstock_1979081900-100963280-orig.jpg?quality=50&strip=all&w=1024)\n\nCredit: aappp \/ Shutterstock\n\nThere are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this.\n\nThe **for** and **while** commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques.\n\n## Using while\nOne of the easiest forever-loops involves using the **while** command followed by the condition “true”. You don’t have to bother with logic like while \\[ 1 -eq 1 \\] or similar tests. The **while true** test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example:\n\n```\n$ while true\n> do\n>   echo Keep running\n>   sleep 3\n> done\nKeep running \nKeep running \nKeep running \n^C\n```\nThe command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once\\!\n```\n$ while false\n> do\n>   echo Keep running\n>   sleep 3\n> done\n$\n```\nYou can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it.\n```\nwhile :\ndo\n\techo Keep running\n\tsleep 3\ndone\n```\nIf you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below.\n\n```\nwhile :\ndo\n\techo Keep running\n\techo \"Press CTRL+C to exit\"\n\tsleep 3\ndone\n```\nYou can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below.\n```\nwhile true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done\n```\nThe command below would work the same. I prefer **while true** because it seems obvious, but any of the examples shown will work as does this one:\n```\nwhile [ 1 ]\ndo\n\techo Keep running\n\techo \"Press CTRL+C to exit\"\n\tsleep 3\ndone\n```\n## **Using for**\nThe **for** command also provides an easy way to loop forever. While not quite as obvious as the **while true** option, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this:\n```\n$ for (int i = 0; i < 5; i++)\n```\nInstead, use the **for** command with no such values as in the example below.\n```\n$ for (( ; ; ))\n> do\n>    echo Keep your spirits up\n>    echo “Press CTRL+C to exit”\n>    sleep 3\n> done\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\n```\nAnd, obviously, press CTRL-C when you want to exit the loop.\n\n## Why loop forever?\nOf course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the **date** command with the **\\+%H** option to check the time, then reminds you that it’s time to go home and exits. The **sleep 60** command was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time.\n\n```\n#!\/bin\/bash\n\nwhile true\ndo\n  if [ `date +%H` -ge 17 ]; then\n    echo Time to go home\n    exit\t# exit script\n  else\n    sleep 60\n  fi\ndone\n```\nIf you want to exit the loop instead of exiting the script, you can use a [**break** command](https:\/\/www.networkworld.com\/article\/971492\/using-break-and-continue-to-exit-loops-in-bash.html) instead of an exit command as shown in the example below.\n```\n#!\/bin\/bash\n\nwhile true\ndo\n  if [ `date +%H` -ge 17 ]; then\n    break\t# exit loop\n  fi\n  echo Time to go home\ndone\n```\n## Wrap-up\nLooping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use.\n\nMore Linux tips and how-tos:\n\n- [Cleaning up with apt-get](https:\/\/www.networkworld.com\/article\/968090\/cleaning-up-with-apt-get.html)\n- [How the Linux screen tool can save your tasks – and your sanity – if SSH is interrupted](https:\/\/www.networkworld.com\/article\/967925\/how-the-linux-screen-tool-can-save-your-tasks-and-your-sanity-if-ssh-is-interrupted.html)\n- [Using ClamAV to detect viruses on Linux](https:\/\/www.networkworld.com\/article\/970780\/using-clamav-to-detect-and-remove-viruses-on-linux.html)\n- [Digging up IP addresses with the Linux dig command](https:\/\/www.networkworld.com\/article\/968394\/digging-up-ip-addresses-with-the-dig-command.html)\n- [Checking Linux system performance with sar](https:\/\/www.networkworld.com\/article\/969982\/checking-linux-system-performance-with-sar.html)\n\n[Linux](https:\/\/www.networkworld.com\/linux\/)\n\n## Related content\n[Opinion Protecting iOS against the aLTEr attacks By Aaron Woland Jul 10, 2018 5 mins Mobile Security Network Security Small and Medium Business](https:\/\/www.networkworld.com\/article\/966012\/protecting-ios-against-the-alter-attacks.html)\n\n[Analysis Rapid7 demystifies penetration testing By Sandra Henry Stocker Feb 8, 2017 3 mins Data Center IT Leadership Network Security](https:\/\/www.networkworld.com\/article\/960143\/rapid7-demystifies-penetration-testing.html)\n\n[Reviews Book review — The Book of R: A First Course in Programming and Statistics By Sandra Henry Stocker Oct 11, 2016 4 mins Data Center Open Source Operating Systems](https:\/\/www.networkworld.com\/article\/956194\/book-review-the-book-of-r-a-first-course-in-programming-and-statistics.html)\n\n[How-To EZ file extraction on Unix By Sandra Henry Stocker Aug 22, 2016 4 mins Data Center Operating Systems](https:\/\/www.networkworld.com\/article\/954532\/ez-file-extraction-on-unix.html)\n\n## Other Sections\n- [PODCASTS](https:\/\/networkworld.com\/podcasts\/)\n- [VIDEOS](https:\/\/networkworld.com\/videos\/)\n- [RESOURCES](https:\/\/us.resources.networkworld.com\/)\n- [EVENTS](https:\/\/networkworld.com\/events\/)\n\nSUBSCRIBE TO OUR NEWSLETTER\n\n### From our editors straight to your inbox\nGet started by entering your email address below.\n\n![sandra\\_henrystocker](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/06\/2004-0-39498900-1750715051-sandra_h-s-3-100646724-orig.jpg?quality=50&strip=all&w=188)\n\nby  [Sandra Henry Stocker](https:\/\/www.networkworld.com\/profile\/sandra-henry-stocker\/)\n\nUnix Dweeb\n\n1. [Follow Sandra Henry Stocker on X](https:\/\/www.twitter.com\/bugfarm)\n2. [Follow Sandra Henry Stocker on Facebook](https:\/\/www.facebook.com\/bugfarm)\n\nSandra Henry-Stocker was a programmer, Linux systems administrator, security engineer and Linux journalist for most of her 30-year career. She describes herself as \"USL\" (Unix as a second language) but remembers enough English to write books and buy groceries. She lives in the mountains in Virginia where, when not working with or writing about Unix, she's chasing the bears away from her bird feeders. Tune into her [2-Minute Linux](https:\/\/www.youtube.com\/playlist?list=PLYaGSokOr0MN-fXA0snsiEd1rFcqSGbow) video tutorials and take command of your command line.\n\n## More from this author\n- [how-toParameter expansion on Linux Jun 23, 2025 4 mins](https:\/\/www.networkworld.com\/article\/4011151\/parameter-expansion-on-linux.html)\n- [how-toEssential commands for Linux server management Jun 17, 2025 6 mins](https:\/\/www.networkworld.com\/article\/4008320\/essential-commands-for-linux-server-management.html)\n- [opinionWhy people love Linux Jun 13, 2025 3 mins](https:\/\/www.networkworld.com\/article\/4006773\/why-people-love-linux.html)\n- [how-toUnderstanding devices on Linux systems Jun 4, 2025 6 mins](https:\/\/www.networkworld.com\/article\/4001959\/understanding-devices-on-linux-systems.html)\n- [how-toMany ways to use the date command on Linux May 27, 2025 4 mins](https:\/\/www.networkworld.com\/article\/3996032\/many-ways-to-use-the-date-command-on-linux.html)\n- [how-toMore math on the Linux command line May 8, 2025 5 mins](https:\/\/www.networkworld.com\/article\/3981326\/more-math-on-the-linux-command-line.html)\n- [how-toMaking use of your command history on Linux Apr 22, 2025 6 mins](https:\/\/www.networkworld.com\/article\/3542724\/making-use-of-command-history-on-linux.html)\n- [how-to18 essential commands for new Linux users Apr 22, 2025 10 mins](https:\/\/www.networkworld.com\/article\/3958246\/18-essential-commands-for-new-linux-users.html)\n\n## Show me more\nPopular\n\nArticles\n\nPodcasts\n\nVideos\n\n[news French government take Bull by horns for €404 million By Maxwell Cooter Apr 3, 20262 mins High-Performance ComputingMergers and AcquisitionsSupercomputers ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2026\/04\/4154186-0-22953600-1775234814-Atos-BullSequana-XH3000.jpg?quality=50&strip=all&w=375)](https:\/\/www.networkworld.com\/article\/4154186\/french-government-take-bull-by-horns-for-e404-million.html)\n\n[news CERT-EU blames Trivy supply chain attack for Europa.eu data breach By John E. Dunn Apr 3, 20264 mins Cloud SecurityCode SecuritySecurity ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2026\/04\/4154185-0-54659100-1775234307-id-2957848-dsc00283-100601236-orig.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/article\/4154185\/cert-eu-blames-trivy-supply-chain-attack-for-europa-eu-data-breach-2.html)\n\n[news Cisco: Latest news and insights By Network World staff Apr 3, 202640 mins Network Management SoftwareNetwork SecurityNetworking ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2026\/04\/3523958-0-68347700-1775245789-csico_logo.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/article\/3523958\/cisco-latest-news-and-insights.html)\n\n[podcast Has the hype around ‘Internet of Things’ paid off? \\| Ep. 145 Apr 18, 202436 mins IoT PlatformsIoT Security ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2024\/04\/nw-thumb-iot-episode-1.jpeg?quality=50&strip=all&w=320)](https:\/\/www.networkworld.com\/podcast\/2093399\/has-the-hype-around-internet-of-things-paid-off-ep-145.html)\n\n[podcast Episode 1: Understanding Cisco’s Converged SDN Transport Sep 24, 202120 mins Cisco SystemsInternetNetworking ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2023\/11\/iStock-1132912672-1-1.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/podcast\/663051\/episode-1-understanding-cisco-s-converged-sdn-transport.html)\n\n[podcast Episode 2: Pluggable Optics and the Internet for the Future Sep 23, 202117 mins Cisco SystemsComputers and PeripheralsInternet ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2023\/11\/episode-2-100908797-orig.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/podcast\/663053\/pluggable-optics-and-the-internet-for-the-future.html)\n\n[video Master Linux Math with the bc Command \\| Easy CLI Calculations Explained! Jun 23, 20251 mins Operating Systems ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/06\/4011089-0-94386400-1750691632-youtube-thumbnail-iOn2hKG4r1g_bf1d19.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/video\/4011089\/master-linux-math-with-the-bc-command-easy-cli-calculations-explained.html)\n\n[video Master Linux Math in Seconds: How to Use the expr Command Like a Pro Jun 17, 20251 mins Operating Systems ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/06\/4008334-0-25623800-1750169271-youtube-thumbnail-xMZtgqVK5ws_1fcb3d.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/video\/4008334\/master-linux-math-in-seconds-how-to-use-the-expr-command-like-a-pro.html)\n\n[video How to Do Math in the Command Line Using Double Parentheses Jun 6, 20251 mins Operating Systems ![Image](https:\/\/www.networkworld.com\/wp-content\/uploads\/2025\/06\/4003180-0-10579600-1749219962-youtube-thumbnail-BnCTtihBbBg_a9be27.jpg?quality=50&strip=all&w=444)](https:\/\/www.networkworld.com\/video\/4003180\/how-to-do-math-in-the-command-line-using-double-parentheses.html)\n\nAbout\n\n- [About Us](https:\/\/www.networkworld.com\/about-us\/)\n- [Advertise](https:\/\/foundryco.com\/our-brands\/networkworld\/)\n- [Contact Us](https:\/\/www.networkworld.com\/contact-us\/)\n- [Editorial Ethics Policy](https:\/\/www.networkworld.com\/editorial-ethics-policy\/)\n- [Foundry Careers](https:\/\/foundryco.com\/work-here\/)\n- [Reprints](https:\/\/www.networkworld.com\/contact-us\/#republication-permissions)\n- [Newsletters](https:\/\/www.networkworld.com\/newsletters\/signup\/)\n- [BrandPosts](https:\/\/www.networkworld.com\/brandposts\/)\n- [News](https:\/\/www.networkworld.com\/news\/)\n- [Features](https:\/\/www.networkworld.com\/feature\/)\n- [Blogs\/Opinion](https:\/\/www.networkworld.com\/blogs\/)\n- [Add Network World as a Preferred Source in Google Search](https:\/\/www.google.com\/preferences\/source?q=networkworld.com)\n\nPolicies\n\n- [Terms of Service](https:\/\/foundryco.com\/terms-of-service-agreement\/)\n- [Privacy Policy](https:\/\/foundryco.com\/privacy-policy\/)\n- [Cookie Policy](https:\/\/foundryco.com\/cookie-policy\/)\n- [Copyright Notice](https:\/\/foundryco.com\/copyright-notice\/)\n- [Member Preferences](https:\/\/www.networkworld.com\/member-preferences\/)\n- [About AdChoices](https:\/\/foundryco.com\/ad-choices\/)\n- [Your California Privacy Rights](https:\/\/foundryco.com\/ccpa\/)\n- [Privacy Settings]()\n\nOur Network\n\n- [CIO](https:\/\/www.cio.com\/)\n- [Computerworld](https:\/\/www.computerworld.com\/)\n- [CSO Online](https:\/\/www.csoonline.com\/)\n- [InfoWorld](https:\/\/www.infoworld.com\/)\n\n- [Facebook](https:\/\/www.facebook.com\/NetworkWorld)\n- [X](https:\/\/twitter.com\/networkworld)\n- [YouTube](https:\/\/www.youtube.com\/idgtechtalk)\n- [Google News](https:\/\/news.google.com\/publications\/CAAqLAgKIiZDQklTRmdnTWFoSUtFRzVsZEhkdmNtdDNiM0pzWkM1amIyMG9BQVAB)\n- [LinkedIn](https:\/\/www.linkedin.com\/company\/network-world)\n\n[© 2026 FoundryCo, Inc. All Rights Reserved.](https:\/\/foundryco.com\/terms-of-service-agreement\/)","attrs_readable_markdown":"There are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this.\n\nThe **for** and **while** commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques.\n\n## Using while\nOne of the easiest forever-loops involves using the **while** command followed by the condition “true”. You don’t have to bother with logic like while \\[ 1 -eq 1 \\] or similar tests. The **while true** test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example:\n\n```\n$ while true\n> do\n>   echo Keep running\n>   sleep 3\n> done\nKeep running \nKeep running \nKeep running \n^C\n```\nThe command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once\\!\n```\n$ while false\n> do\n>   echo Keep running\n>   sleep 3\n> done\n$\n```\nYou can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it.\n```\nwhile :\ndo\n\techo Keep running\n\tsleep 3\ndone\n```\nIf you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below.\n\n```\nwhile :\ndo\n\techo Keep running\n\techo \"Press CTRL+C to exit\"\n\tsleep 3\ndone\n```\nYou can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below.\n```\nwhile true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done\n```\nThe command below would work the same. I prefer **while true** because it seems obvious, but any of the examples shown will work as does this one:\n```\nwhile [ 1 ]\ndo\n\techo Keep running\n\techo \"Press CTRL+C to exit\"\n\tsleep 3\ndone\n```\n## **Using for**\nThe **for** command also provides an easy way to loop forever. While not quite as obvious as the **while true** option, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this:\n```\n$ for (int i = 0; i < 5; i++)\n```\nInstead, use the **for** command with no such values as in the example below.\n```\n$ for (( ; ; ))\n> do\n>    echo Keep your spirits up\n>    echo “Press CTRL+C to exit”\n>    sleep 3\n> done\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\nKeep your spirits up\n“Press CTRL+C to exit“\n```\nAnd, obviously, press CTRL-C when you want to exit the loop.\n\n## Why loop forever?\nOf course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the **date** command with the **\\+%H** option to check the time, then reminds you that it’s time to go home and exits. The **sleep 60** command was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time.\n\n```\n#!\/bin\/bashwhile true\ndo\n if [ `date +%H` -ge 17 ]; then\n echo Time to go home\n exit # exit script\n else\n sleep 60\n fi\ndone\n```\nIf you want to exit the loop instead of exiting the script, you can use a [**break** command](https:\/\/www.networkworld.com\/article\/971492\/using-break-and-continue-to-exit-loops-in-bash.html) instead of an exit command as shown in the example below.\n```\n#!\/bin\/bashwhile true\ndo\n if [ `date +%H` -ge 17 ]; then\n break # exit loop\n fi\n echo Time to go home\ndone\n```\n## Wrap-up\nLooping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use.\n\nMore Linux tips and how-tos:","meta_canonical":null}

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Boilerpipe Text	There are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this. The for and while commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques. Using while One of the easiest forever-loops involves using the while command followed by the condition “true”. You don’t have to bother with logic like while [ 1 -eq 1 ] or similar tests. The while true test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example: $ while true > do > echo Keep running > sleep 3 > done Keep running Keep running Keep running ^C The command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once! $ while false > do > echo Keep running > sleep 3 > done $ You can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it. while : do echo Keep running sleep 3 done If you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below. while : do echo Keep running echo "Press CTRL+C to exit" sleep 3 done You can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below. while true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done The command below would work the same. I prefer while true because it seems obvious, but any of the examples shown will work as does this one: while [ 1 ] do echo Keep running echo "Press CTRL+C to exit" sleep 3 done Using for The for command also provides an easy way to loop forever. While not quite as obvious as the while true option, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this: $ for (int i = 0; i < 5; i++) Instead, use the for command with no such values as in the example below. $ for (( ; ; )) > do > echo Keep your spirits up > echo “Press CTRL+C to exit” > sleep 3 > done Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ And, obviously, press CTRL-C when you want to exit the loop. Why loop forever? Of course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the date command with the +%H option to check the time, then reminds you that it’s time to go home and exits. The sleep 60 command was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time. #!/bin/bash while true do if [ `date +%H` -ge 17 ]; then echo Time to go home exit # exit script else sleep 60 fi done If you want to exit the loop instead of exiting the script, you can use a break command instead of an exit command as shown in the example below. #!/bin/bash while true do if [ `date +%H` -ge 17 ]; then break # exit loop fi echo Time to go home done Wrap-up Looping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use. More Linux tips and how-tos:
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[Home](https://www.networkworld.com/) 2. [Blogs](https://www.networkworld.com/blogs/) 3. [Unix as a Second Language](https://www.networkworld.com/blogs/unix-as-a-second-language/) ![sandra\_henrystocker](https://www.networkworld.com/wp-content/uploads/2025/06/2004-0-39498900-1750715051-sandra_h-s-3-100646724-orig.jpg?quality=50&strip=all&w=113) by [Sandra Henry Stocker](https://www.networkworld.com/profile/sandra-henry-stocker/) Unix Dweeb # How to loop forever in bash How-To Nov 6, 20245 mins ## Looping forever is easy if you know what commands you want to run repeatedly and the conditions under which you want them to stop running. ![upside down roller coaster in a loop against a cloud and blue sky amusement park](https://www.networkworld.com/wp-content/uploads/2025/02/3600146-0-40350400-1740688644-shutterstock_1979081900-100963280-orig.jpg?quality=50&strip=all&w=1024) Credit: aappp / Shutterstock There are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this. The for and while commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques. ## Using while One of the easiest forever-loops involves using the while command followed by the condition “true”. You don’t have to bother with logic like while \[ 1 -eq 1 \] or similar tests. The while true test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example: ``` $ while true > do > echo Keep running > sleep 3 > done Keep running Keep running Keep running ^C ``` The command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once\! ``` $ while false > do > echo Keep running > sleep 3 > done $ ``` You can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it. ``` while : do echo Keep running sleep 3 done ``` If you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below. ``` while : do echo Keep running echo "Press CTRL+C to exit" sleep 3 done ``` You can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below. ``` while true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done ``` The command below would work the same. I prefer while true because it seems obvious, but any of the examples shown will work as does this one: ``` while [ 1 ] do echo Keep running echo "Press CTRL+C to exit" sleep 3 done ``` ## Using for The for command also provides an easy way to loop forever. While not quite as obvious as the while true option, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this: ``` $ for (int i = 0; i < 5; i++) ``` Instead, use the for command with no such values as in the example below. ``` $ for (( ; ; )) > do > echo Keep your spirits up > echo “Press CTRL+C to exit” > sleep 3 > done Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ ``` And, obviously, press CTRL-C when you want to exit the loop. ## Why loop forever? Of course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the date command with the \+%H option to check the time, then reminds you that it’s time to go home and exits. The sleep 60 command was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time. ``` #!/bin/bash while true do if [ `date +%H` -ge 17 ]; then echo Time to go home exit # exit script else sleep 60 fi done ``` If you want to exit the loop instead of exiting the script, you can use a [break command](https://www.networkworld.com/article/971492/using-break-and-continue-to-exit-loops-in-bash.html) instead of an exit command as shown in the example below. ``` #!/bin/bash while true do if [ `date +%H` -ge 17 ]; then break # exit loop fi echo Time to go home done ``` ## Wrap-up Looping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use. More Linux tips and how-tos: - [Cleaning up with apt-get](https://www.networkworld.com/article/968090/cleaning-up-with-apt-get.html) - [How the Linux screen tool can save your tasks – and your sanity – if SSH is interrupted](https://www.networkworld.com/article/967925/how-the-linux-screen-tool-can-save-your-tasks-and-your-sanity-if-ssh-is-interrupted.html) - [Using ClamAV to detect viruses on Linux](https://www.networkworld.com/article/970780/using-clamav-to-detect-and-remove-viruses-on-linux.html) - [Digging up IP addresses with the Linux dig command](https://www.networkworld.com/article/968394/digging-up-ip-addresses-with-the-dig-command.html) - [Checking Linux system performance with sar](https://www.networkworld.com/article/969982/checking-linux-system-performance-with-sar.html) [Linux](https://www.networkworld.com/linux/) ## Related content [Opinion Protecting iOS against the aLTEr attacks By Aaron Woland Jul 10, 2018 5 mins Mobile Security Network Security Small and Medium Business](https://www.networkworld.com/article/966012/protecting-ios-against-the-alter-attacks.html) [Analysis Rapid7 demystifies penetration testing By Sandra Henry Stocker Feb 8, 2017 3 mins Data Center IT Leadership Network Security](https://www.networkworld.com/article/960143/rapid7-demystifies-penetration-testing.html) [Reviews Book review — The Book of R: A First Course in Programming and Statistics By Sandra Henry Stocker Oct 11, 2016 4 mins Data Center Open Source Operating Systems](https://www.networkworld.com/article/956194/book-review-the-book-of-r-a-first-course-in-programming-and-statistics.html) [How-To EZ file extraction on Unix By Sandra Henry Stocker Aug 22, 2016 4 mins Data Center Operating Systems](https://www.networkworld.com/article/954532/ez-file-extraction-on-unix.html) ## Other Sections - [PODCASTS](https://networkworld.com/podcasts/) - [VIDEOS](https://networkworld.com/videos/) - [RESOURCES](https://us.resources.networkworld.com/) - [EVENTS](https://networkworld.com/events/) SUBSCRIBE TO OUR NEWSLETTER ### From our editors straight to your inbox Get started by entering your email address below. ![sandra\_henrystocker](https://www.networkworld.com/wp-content/uploads/2025/06/2004-0-39498900-1750715051-sandra_h-s-3-100646724-orig.jpg?quality=50&strip=all&w=188) by [Sandra Henry Stocker](https://www.networkworld.com/profile/sandra-henry-stocker/) Unix Dweeb 1. [Follow Sandra Henry Stocker on X](https://www.twitter.com/bugfarm) 2. [Follow Sandra Henry Stocker on Facebook](https://www.facebook.com/bugfarm) Sandra Henry-Stocker was a programmer, Linux systems administrator, security engineer and Linux journalist for most of her 30-year career. She describes herself as "USL" (Unix as a second language) but remembers enough English to write books and buy groceries. She lives in the mountains in Virginia where, when not working with or writing about Unix, she's chasing the bears away from her bird feeders. 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Readable Markdown	There are several ways to loop “forever” on Linux commands. In practice, this means only until you decide to stop looping. You might do this while typing commands on the command line, or, more likely, within your scripts. It’s quite easy. This post provides some examples of how to do this. The for and while commands will provide what you need. There are only a few things you have to keep in mind with respect to syntax and techniques. ## Using while One of the easiest forever-loops involves using the while command followed by the condition “true”. You don’t have to bother with logic like while \[ 1 -eq 1 \] or similar tests. The while true test means the loop will run until you stop it with CTRL-C, close the terminal window, log out, or restart the system. After all, true is always true. Here’s an example: ``` $ while true > do > echo Keep running > sleep 3 > done Keep running Keep running Keep running ^C ``` The command in the example above will continue running, echo “Keep running” after every three-second break. Try “while false” and it won’t loop even once\! ``` $ while false > do > echo Keep running > sleep 3 > done $ ``` You can do the same thing with a “while :” test if you prefer. The key here is that the colon always yields success. Like “while true”, this test will never fail and the loop just keeps running. The syntax is just a bit less obvious to anyone who isn’t used to using it. ``` while : do echo Keep running sleep 3 done ``` If you’ve inserted an infinite loop into a script and want to remind the person who is using it how to exit the script, you can always provide a little guidance as in the example below. ``` while : do echo Keep running echo "Press CTRL+C to exit" sleep 3 done ``` You can do the same thing in a single line by separating the lines shown above with semicolons as shown in the example below. ``` while true; do echo Keep running; echo 'Press CTRL+C'; sleep 3; done ``` The command below would work the same. I prefer while true because it seems obvious, but any of the examples shown will work as does this one: ``` while [ 1 ] do echo Keep running echo "Press CTRL+C to exit" sleep 3 done ``` ## Using for The for command also provides an easy way to loop forever. While not quite as obvious as the while true option, the syntax is reasonably straightforward. You can just replace the parameters in a normal for loop (the start, condition and increment values) that would generally look something like this: ``` $ for (int i = 0; i < 5; i++) ``` Instead, use the for command with no such values as in the example below. ``` $ for (( ; ; )) > do > echo Keep your spirits up > echo “Press CTRL+C to exit” > sleep 3 > done Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ Keep your spirits up “Press CTRL+C to exit“ ``` And, obviously, press CTRL-C when you want to exit the loop. ## Why loop forever? Of course, you’re not ever going to want to loop forever, but having loops run until you stop them can often be very useful. The script below runs until 5:00 p.m. It uses the date command with the \+%H option to check the time, then reminds you that it’s time to go home and exits. The sleep 60 command was included to limit the time checking to once a minute. Otherwise, this script could gobble up a lot of CPU time. ``` #!/bin/bashwhile true do if [ `date +%H` -ge 17 ]; then echo Time to go home exit # exit script else sleep 60 fi done ``` If you want to exit the loop instead of exiting the script, you can use a [break command](https://www.networkworld.com/article/971492/using-break-and-continue-to-exit-loops-in-bash.html) instead of an exit command as shown in the example below. ``` #!/bin/bashwhile true do if [ `date +%H` -ge 17 ]; then break # exit loop fi echo Time to go home done ``` ## Wrap-up Looping forever is easy. Determining what commands you want to run repeatedly and the conditions under which you want them to stop running are the only challenging parts of putting these forever loops into use. More Linux tips and how-tos:
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