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chmod ⚬ˢʰ｜Definition｜1st｜20260523112457-00-⌔

chmod - Wikipedia

chmod

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chmod is a shell command for changing access permissions and special mode flags of files (including special files such as directories). The name is short for * change mode* where mode refers to the permissions and flags collectively.12

The command originated in AT&T Unix version 1 and was exclusive to Unix and Unix-like operating systems until it was ported to other operating systems such as Windows (in UnxUtils)3 and IBM i.4

In Unix and Unix-like operating systems, a system call with the same name as the command, chmod(), provides access to the underlying access control data. The command exposes the capabilities of the system call to a shell user.

As the need for enhanced file-system permissions grew, access-control lists5 were added to many file systems to augment the modes controlled via chmod.

The implementation of chmod bundled in GNU coreutils was written by David MacKenzie and Jim Meyering.6

Printed 2026-06-28.

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Footnotes

  1. The modes/permissions are shown when listing files in long format. ↩

  2. “Tutorial for chmod”. catcode.com. Archived from the original on 20 May 2000. Retrieved 26 August 2008. ↩

  3. “Native Win32 ports of some GNU utilities”. unxutils.sourceforge.net. Archived from the original on 9 February 2006. Retrieved 9 August 2025. ↩

  4. IBM. “IBM System i Version 7.2 Programming Qshell” (PDF). IBM. Archived (PDF) from the original on 18 September 2020. Retrieved 5 September 2020. ↩

  5. “AIX 5.3 System management”. IBM knowledge Center. IBM. Archived from the original on 4 March 2016. Retrieved 30 August 2015. ↩

  6. “chmod(1): change file mode bits - Linux man page”. linux.die.net. Archived from the original on 9 January 2019. Retrieved 6 January 2019. ↩

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chmod ⚬ˢʰ｜docu｜1st｜20251021001049-00-◊

chmod(1) - Linux manual page
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