chmod

(file system)("Change mode") The Unix command and system call to change the access permissions of a named file.Each file (directory, device, etc.) has nine kinds of accesswhich can be allowed or denied. Different permissions applyto the owner of the file, the members of the group the filebelongs to, and all users. Each of these classes of user(owner, group and other) can have permission to read, write orexecute the file. Chmod can also set various other mode bitsfor a file or directory such as the sticky bit and the set user id bit.

Unix man page: chmod

chmod

(CHange MODe) A Unix command that changes the permissions (attributes) of a file or directory. Chmod requires an understanding of how the read-write-execute permissions are expressed. The "list long" command (ls -l) displays the attributes of a file or directory, and the first part of the line looks like this: -rwxrwxrwx. A dash or "d" as the first character means file or directory. The three sets of rwx are permissions for owner-group-other. For example, -rwxrw-r-- gives all permissions to the file on the line to the owner, read/write permissions to the group and read only for the rest.

The command uses =, + and - to set, add and subtract changes to owner (u), group (g), other (o) or all (a). The following examples show the permissions of an abc.sh shell script after each command is executed. See ls, shell script, chown and chgrp.

-rwxrwxrwx ALL PERMISSIONS chmod o= abc.sh SET OTHER TO NONE -rwxrwx--- chmod o+r abc.sh ADD R TO OTHER -rwxrwxr-- chmod a-x abc.sh REMOVE ALL EXECUTE -rw-rw-r-- chmod a=rwx abc.sh SET ALL TO RWX -rwxrwxrwx chmod a= abc.sh SET ALL TO NON ---------- chmod u=r abc.sh SET OWNER TO READ -r--------

List Long Shows Permissions

The list long (ls -l) command shows the permissions of files and directories (folders). The arrow points to the permissions in this Mac OS X example (X stands for Unix).

chmod

chmod

chmod

CHMOD