CHMOD(1) User Commands CHMOD(1)
NAME
 chmod - change file mode bits
SYNOPSIS
 chmod [OPTION]... MODE[,MODE]... FILE...
 chmod [OPTION]... OCTAL-MODE FILE...
 chmod [OPTION]... --reference=RFILE FILE...
DESCRIPTION
 This manual page documents the GNU version of chmod. chmod changes the
 file mode bits of each given file according to mode, which can be ei-
 ther a symbolic representation of changes to make, or an octal number
 representing the bit pattern for the new mode bits.
 The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where
 perms is either zero or more letters from the set rwxXst, or a single
 letter from the set ugo. Multiple symbolic modes can be given, sepa-
 rated by commas.
 A combination of the letters ugoa controls which users' access to the
 file will be changed: the user who owns it (u), other users in the
 file's group (g), other users not in the file's group (o), or all users
 (a). If none of these are given, the effect is as if (a) were given,
 but bits that are set in the umask are not affected.
 The operator + causes the selected file mode bits to be added to the
 existing file mode bits of each file; - causes them to be removed; and
 = causes them to be added and causes unmentioned bits to be removed ex-
 cept that a directory's unmentioned set user and group ID bits are not
 affected.
 The letters rwxXst select file mode bits for the affected users: read
 (r), write (w), execute (or search for directories) (x), execute/search
 only if the file is a directory or already has execute permission for
 some user (X), set user or group ID on execution (s), restricted dele-
 tion flag or sticky bit (t). Instead of one or more of these letters,
 you can specify exactly one of the letters ugo: the permissions granted
 to the user who owns the file (u), the permissions granted to other
 users who are members of the file's group (g), and the permissions
 granted to users that are in neither of the two preceding categories
 (o).
 A numeric mode is from one to four octal digits (0-7), derived by
 adding up the bits with values 4, 2, and 1. Omitted digits are assumed
 to be leading zeros. The first digit selects the set user ID (4) and
 set group ID (2) and restricted deletion or sticky (1) attributes. The
 second digit selects permissions for the user who owns the file: read
 (4), write (2), and execute (1); the third selects permissions for
 other users in the file's group, with the same values; and the fourth
 for other users not in the file's group, with the same values.
 chmod never changes the permissions of symbolic links; the chmod system
 call cannot change their permissions. This is not a problem since the
 permissions of symbolic links are never used. However, for each sym-
 bolic link listed on the command line, chmod changes the permissions of
 the pointed-to file. In contrast, chmod ignores symbolic links encoun-
 tered during recursive directory traversals.
SETUID AND SETGID BITS
 chmod clears the set-group-ID bit of a regular file if the file's group
 ID does not match the user's effective group ID or one of the user's
 supplementary group IDs, unless the user has appropriate privileges.
 Additional restrictions may cause the set-user-ID and set-group-ID bits
 of MODE or RFILE to be ignored. This behavior depends on the policy
 and functionality of the underlying chmod system call. When in doubt,
 check the underlying system behavior.
 For directories chmod preserves set-user-ID and set-group-ID bits un-
 less you explicitly specify otherwise. You can set or clear the bits
 with symbolic modes like u+s and g-s. To clear these bits for directo-
 ries with a numeric mode requires an additional leading zero, or lead-
 ing = like 00755 , or =755
RESTRICTED DELETION FLAG OR STICKY BIT
 The restricted deletion flag or sticky bit is a single bit, whose in-
 terpretation depends on the file type. For directories, it prevents
 unprivileged users from removing or renaming a file in the directory
 unless they own the file or the directory; this is called the re-
 stricted deletion flag for the directory, and is commonly found on
 world-writable directories like /tmp. For regular files on some older
 systems, the bit saves the program's text image on the swap device so
 it will load more quickly when run; this is called the sticky bit.
OPTIONS
 Change the mode of each FILE to MODE. With --reference, change the
 mode of each FILE to that of RFILE.
 -c, --changes
 like verbose but report only when a change is made
 -f, --silent, --quiet
 suppress most error messages
 -v, --verbose
 output a diagnostic for every file processed
 --no-preserve-root
 do not treat '/' specially (the default)
 --preserve-root
 fail to operate recursively on '/'
 --reference=RFILE
 use RFILE's mode instead of MODE values
 -R, --recursive
 change files and directories recursively
 --help display this help and exit
 --version
 output version information and exit
 Each MODE is of the form
 '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
AUTHOR
 Written by David MacKenzie and Jim Meyering.
REPORTING BUGS
 GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
 Report any translation bugs to <https://translationproject.org/team/>
COPYRIGHT
 Copyright (C) 2020 Free Software Foundation, Inc. License GPLv3+: GNU
 GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
 This is free software: you are free to change and redistribute it.
 There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
 chmod(2)
 Full documentation <https://www.gnu.org/software/coreutils/chmod>
 or available locally via: info '(coreutils) chmod invocation'
GNU coreutils 8.32 February 2024 CHMOD(1)