chmod—Change the access permissions of files
chmod [–Rcfv] [—recursive] [—changes] [—silent] [—quiet] [—verbose] [—help] [—version] mode file…
This manual page documents the GNU version of
The format of a symbolic mode is [ugoa…][[+-=][rwxXstugo…]…][,…]. Multiple symbolic operations can be given, separated by commas.
A combination of the letters
The operator + causes the permissions selected to be added to the existing permissions of each file; – causes them to be removed
The letters rwxXstugo select the new permissions for the affected users: read (r), write (w), execute (or access for directories) (x), execute only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), save program text on swap device (t), the permissions that the user who owns the file currently has for it (u), the permissions that other users in the file’s group have for it (g), and the permissions that other users not in the file’s group have for it (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. Any omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and save text image (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.
|–c, —changes||Verbosely describe only files whose permissions actually change.|
|–f, —silent, —quiet||Do not print error messages about files whose permissions cannot be changed.|
|–v, —verbose||Verbosely describe changed permissions.|
|–R, —recursive||Recursively change permissions of directories and their contents.|
|—help||Print a usage message on standard output and exit successfully.|
|—version||Print version information on standard output, then exit successfully.|