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chmod(1)                         User Commands                        chmod(1)


       chmod - change file mode bits


       chmod [OPTION]... MODE[,MODE]... FILE...
       chmod [OPTION]... OCTAL-MODE FILE...
       chmod [OPTION]... --reference=RFILE FILE...


       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
       either 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,
       separated 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
       except 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
       deletion 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 doesn't change the permissions of symbolic links; the chmod
       system call cannot change their permissions on most systems, and most
       systems ignore permissions of symbolic links.  However, for each
       symbolic link listed on the command line, chmod changes the permissions
       of the pointed-to file.  In contrast, chmod ignores symbolic links
       encountered during recursive directory traversals. Options that modify
       this behavior are described in the OPTIONS section.


       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
       unless 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
       directories with a numeric mode requires an additional leading zero
       like 00755, leading minus like -6000, or leading equals like =755.


       The restricted deletion flag or sticky bit is a single bit, whose
       interpretation 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
       restricted 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.


       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

              affect the referent of each symbolic link, rather than the
              symbolic link itself

       -h, --no-dereference
              affect each symbolic link, rather than the referent

              do not treat '/' specially (the default)

              fail to operate recursively on '/'

              use RFILE's mode instead of specifying MODE values.  RFILE is
              always dereferenced if a symbolic link.

       -R, --recursive
              change files and directories recursively

       The following options modify how a hierarchy is traversed when the -R
       option is also specified.  If more than one is specified, only the
       final one takes effect. '-H' is the default.

       -H     if a command line argument is a symbolic link to a directory,
              traverse it

       -L     traverse every symbolic link to a directory encountered

       -P     do not traverse any symbolic links

       --help display this help and exit

              output version information and exit

       Each MODE is of the form


       Written by David MacKenzie and Jim Meyering.


       GNU coreutils online help: <>
       Report any translation bugs to <>


       Copyright © 2024 Free Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or later <>.
       This is free software: you are free to change and redistribute it.
       There is NO WARRANTY, to the extent permitted by law.



       Full documentation <>
       or available locally via: info '(coreutils) chmod invocation'

GNU coreutils 9.5                 March 2024                          chmod(1)

coreutils 9.5 - Generated Thu Apr 18 14:16:11 CDT 2024
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