chmod-original(1)

change file mode

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

With the coreutil package (with the extra set), see chmod(1) instead.

Also by this name: chmod(2), System calls

NAME

chmod - change file mode

SYNOPSIS

chmod [ -R ] mode file ...
chmod [ugoa ]{+ |- |=}[ rwxlstugo ] file ...

DESCRIPTION

chmod changes or assigns the mode of a file.  The mode of  a
file  specifies  its  permissions and other attributes.  The
mode may be absolute  or  symbolic.   An  absolute  mode  is
specified using octal numbers:
     chmod nnnn file ...
where n is a number from 0 to 7.  An absolute mode  is  con-
structed from the OR of any of the following modes:

     4000      Set user ID on execution.
     20#0      Set group ID on execution if # is 7, 5, 3, or
               1.
               Enable mandatory locking if # is 6, 4, 2,  or
               0.
               This bit is ignored if the file is  a  direc-
               tory; it may be set or cleared only using the
               symbolic mode.
     1000      Turn on sticky bit [(see chmod(2)].
     0400      Allow read by owner.
     0200      Allow write by owner.
     0100      Allow execute (search in directory) by owner.
     0070      Allow read, write, and  execute  (search)  by
               group.
     0007      Allow read, write, and  execute  (search)  by
               others.
A symbolic mode is specified in the following format:
     chmod [ who ]  operator  [ permission(s) ]   file ...
who is zero or more of the characters u, g, o, and a  speci-
fying whose permissions are to be changed or assigned:
     u         user's permissions
     g         group's permissions
     o         others' permissions
     a         all permissions (user, group, and other)

If who is omitted, it defaults to a.  operator is one of  +,
-, or =, signifying how permissions are to be changed:
     +         Add permissions.
     -         Take away permissions.
     =         Assign permissions absolutely.
Unlike other symbolic operations, = has an  absolute  effect
in that it resets all other bits.  Omitting permission(s) is
useful  only  with  =  to   take   away   all   permissions.
permission(s) is any compatible combination of the following
letters:
     r         read permission

     w         write permission
     x         execute permission
     s         user or group set-ID
     t         sticky bit
     l         mandatory locking
     u, g, o   indicate that permission is to be taken  from
               the current user, group or other mode respec-
               tively.

Permissions to a file may vary depending on your user  iden-
tification  number  (UID)  or  group  identification  number
(GID).  Permissions are described in  three  sequences  each
having three characters:
                    User   Group   Other

                    rwx     rwx     rwx
This example (user, group, and others all have permission to
read,  write,  and  execute  a  given file) demonstrates two
categories for granting permissions:  the access  class  and
the permissions themselves.

Multiple symbolic modes separated by commas may be given, though no spaces may intervene between these modes. Operations are performed in the order given. Multiple symbolic letters following a single operator cause the corresponding operations to be performed simultaneously. The letter s is only meaningful with u or g, and t only works with u.

Mandatory file and record locking (l)  refers  to  a  file's
ability  to  have  its reading or writing permissions locked
while a program is accessing that file.  It is not  possible
to  permit group execution and enable a file to be locked on
execution at the same time.  In addition, it is not possible
to  turn  on  the  set-group-ID  bit and enable a file to be
locked on execution at the same time.  The  following  exam-
ples, therefore, are invalid and elicit error messages:
     chmod g+x,+l file
     chmod g+s,+l file

Only the owner of a file or directory (or the super-user) may change that file's or directory's mode. Only the super-user may set the sticky bit on a non-directory file. If you are not super-user, chmod will mask the sticky-bit but will not return an error. In order to turn on a file's set-group-ID bit, your own group ID must correspond to the file's and group execution must be set. The -R option recursively descends through directory arguments, setting the mode for each file as described above.

EXAMPLES

Deny execute permission to everyone:
     chmod a-x file
Allow read permission to everyone:

     chmod 444 file

Make a file readable and writable by the group and others:
     chmod go+rw file
     chmod 066 file

Cause a file to be locked during access:

     chmod +l file

Allow everyone to read, write, and execute the file and turn
on the set group-ID.
     chmod =rwx,g+s file
     chmod 2777 file

Absolute changes don't work for the set-group-ID bit of a directory. You must use g+s or g-s.

NOTES