chmod(1) [minix man page]
CHMOD(1) General Commands Manual CHMOD(1) NAME
chmod - change access mode for files SYNOPSIS
chmod [-R] mode file ... OPTIONS
-R Change hierarchies recursively EXAMPLES
chmod 755 file # Owner: rwx Group: r-x Others: r-x chmod +x file1 file2 # Make file1 and file2 executable chmod a-w file # Make file read only chmod u+s file # Turn on SETUID for file chmod -R o+w dir # Allow writing for all files in dir DESCRIPTION
The given mode is applied to each file in the file list. If the -R flag is present, the files in a directory will be changed as well. The mode can be either absolute or symbolic. Absolute modes are given as an octal number that represents the new file mode. The mode bits are defined as follows: 4000 Set effective user id on execution to file's owner id 2000 Set effective group id on execution to file's group id 0400 file is readable by the owner of the file 0200 writeable by owner 0100 executable by owner 0070 same as above, for other users in the same group 0007 same as above, for all other users Symbolic modes modify the current file mode in a specified way. The form is: [who] op permissions { op permissions ...} {, [who] op ... } The possibilities for who are u, g, o, and a, standing for user, group, other and all, respectively. If who is omitted, a is assumed, but the current umask is used. The op can be +, -, or =; + turns on the given permissions, - turns them off; = sets the permissions exclu- sively for the given who. For example g=x sets the group permissions to --x. The possible permissions are r, w, x; which stand for read, write, and execute; s turns on the set effective user/group id bits. s only makes sense with u and g; o+s is harmless. SEE ALSO
ls(1), chmod(2). CHMOD(1)
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CHMOD(1) BSD General Commands Manual CHMOD(1) NAME
chmod -- change file modes SYNOPSIS
chmod [-R [-H | -L | -P]] [-fh] mode file ... DESCRIPTION
The chmod utility modifies the file mode bits of the listed files as specified by the mode operand. The options are as follows: -H If the -R option is specified, symbolic links on the command line are followed. (Symbolic links encountered in the tree traversal are not followed.) -L If the -R option is specified, all symbolic links are followed. -P If the -R option is specified, no symbolic links are followed. -R Change the modes of the file hierarchies rooted in the files instead of just the files themselves. -f Do not display a diagnostic message or modify the exit status if chmod fails to change the mode of a file. -h If file is symbolic link, the mode of the link is changed. The -H, -L and -P options are ignored unless the -R option is specified. In addition, these options override each other and the command's actions are determined by the last one specified. Only the owner of a file or the super-user is permitted to change the mode of a file. EXIT STATUS
The chmod utility exits 0 on success, and >0 if an error occurs. MODES
Modes may be absolute or symbolic. An absolute mode is an octal number constructed by or'ing the following values: 4000 set-user-ID-on-execution 2000 set-group-ID-on-execution 1000 sticky bit, see chmod(2) 0400 read by owner 0200 write by owner 0100 execute (or search for directories) by owner 0070 read, write, execute/search by group 0007 read, write, execute/search by others The read, write, and execute/search values for group and others are encoded as described for owner. The symbolic mode is described by the following grammar: mode ::= clause [, clause ...] clause ::= [who ...] [action ...] last_action action ::= op [perm ...] last_action ::= op [perm ...] who ::= a | u | g | o op ::= + | - | = perm ::= r | s | t | w | x | X | u | g | o The who symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts of the mode bits, respectively. The who symbol ``a'' is equivalent to ``ugo''. The perm symbols represent the portions of the mode bits as follows: r The read bits. s The set-user-ID-on-execution and set-group-ID-on-execution bits. t The sticky bit. w The write bits. x The execute/search bits. X The execute/search bits if the file is a directory or any of the execute/search bits are set in the original (unmodified) mode. Operations with the perm symbol ``X'' are only meaningful in conjunction with the op symbol ``+'', and are ignored in all other cases. u The user permission bits in the mode of the original file. g The group permission bits in the mode of the original file. o The other permission bits in the mode of the original file. The op symbols represent the operation performed, as follows: + If no value is supplied for perm, the ``+'' operation has no effect. If no value is supplied for who, each permission bit specified in perm, for which the corresponding bit in the file mode creation mask is clear, is set. Otherwise, the mode bits represented by the specified who and perm values are set. - If no value is supplied for perm, the ``-'' operation has no effect. If no value is supplied for who, each permission bit specified in perm, for which the corresponding bit in the file mode creation mask is clear, is cleared. Otherwise, the mode bits represented by the specified who and perm values are cleared. = The mode bits specified by the who value are cleared, or, if no who value is specified, the owner, group and other mode bits are cleared. Then, if no value is supplied for who, each permission bit specified in perm, for which the corresponding bit in the file mode creation mask is clear, is set. Otherwise, the mode bits represented by the specified who and perm values are set. Each clause specifies one or more operations to be performed on the mode bits, and each operation is applied to the mode bits in the order specified. Operations upon the other permissions only (specified by the symbol ``o'' by itself), in combination with the perm symbols ``s'' or ``t'', are ignored. EXAMPLES
644 make a file readable by anyone and writable by the owner only. go-w deny write permission to group and others. =rw,+X set the read and write permissions to the usual defaults, but retain any execute permissions that are currently set. +X make a directory or file searchable/executable by everyone if it is already searchable/executable by anyone. 755 u=rwx,go=rx u=rwx,go=u-w make a file readable/executable by everyone and writable by the owner only. go= clear all mode bits for group and others. g=u-w set the group bits equal to the user bits, but clear the group write bit. SEE ALSO
chflags(1), install(1), chmod(2), stat(2), umask(2), fts(3), setmode(3), symlink(7), chown(8) STANDARDS
The chmod utility is expected to be IEEE Std 1003.2-1992 (``POSIX.2'') compatible with the exception of the perm symbol ``t'' which is not included in that standard. BUGS
There's no perm option for the naughty bits. BSD
January 22, 2010 BSD