NAME chmod - change file modes SYNOPSIS chmod [-R [-H | -L | -P]] 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. mode of a file. ESCOA 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 en- coded as described for owner. The symbolic mode is described by the following grammar: ESCOA 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 oth- er parts of the mode bits, respectively. The who symbol ``a'' is equiva- lent 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. 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 (unmodi- fied) 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 ef- fect. If no value is supplied for who, each permission bit speci- fied in perm, for which the corresponding bit in the file mode cre- ation 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 ef- fect. If no value is supplied for who, each permission bit speci- ation mask is clear, is cleared. Otherwise, the mode bits repre- sented 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 rep- resented 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 speci- fied. Operations upon the other permissions only (specified by the symbol ``o'' by itself), in combination with the perm symbols ``s'' or ``t'', are ig- nored. EXAMPLES 644 make a file readable by anyone and writable by the owner 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. BUGS SEE ALSO 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 Std1003.2 (``POSIX.2'') compati- ble with the exception of the perm symbols ``t'' and ``X'' which are not included in that standard.