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- CHMOD (1)
-
- NAME
-
- chmod - change file modes
-
- SYNOPSIS
-
- chmod [ R ] 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:
- R - Traverse a file hierarchy. For each file that is of
- type directory, chmod changes the mode of all files in the
- file hierarchy below it followed by the mode of the directo-
- ry itself.
- Symbolic links are not indirected through, nor are their modes
- altered.
- Only the owner of a file or the super-user is permitted to
- change the mode of a file.
- The chmod utility exits 0 on success, and >0 if an error oc-
- curs.
- MODES
-
- Modes may be absolute or symbolic. An absolute mode is an oc-
- tal number constructed by or Ap 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:
- - The read bits.
- - The set-user-ID-on-execution and set-group-ID-on-
- execution bits.
- - The sticky bit.
- - The write bits.
- - The execute/search bits.
- - 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 it
- is ignored in all other cases.
- 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 per-
- mission bit specified in perm , for which the corresponding
- bit in the file mode creation mask is clear, is set. Other-
- wise, 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 , the mode
- bits represented by perm are cleared for the owner, group
- and other permissions. 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 speci-
- fied 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 writeable 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
-
- There's no perm option for the naughty bits.
- SEE ALSO
-
- install (1) , chmod (2) , stat (2) , umask (2) , fts (3) , set-
- mode (3) , chown (8)
- STANDARDS
-
- The chmod utility is expected to be compatible with the excep-
- tion of the perm symbols and which are not included in that stan-
- dard.
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