In Unix, how do I set the default protection to newly created directories and files?
umask command, when placed in the
tcsh shells), the
.profile file (for the Korn shell), or the
.bash_profile file (for the
bash shell), acts as a
umask that screens out permissions automatically each time you
create a new directory or file in your account. If a directory is readable,
writable, and executable by the owner, a selected
group of users, and
everyone on the system, its octal permission is 777. If a
file is readable and writable by the owner, a selected group of users,
and everyone on the system, its octal permission is 666. The
command is followed with a number that is subtracted from 777 on
directories, and from 666 on files. The result gives the default
protection for new directories and files.
Note: You can use the
to set permissions for existing files and directories. For more information
chmod command, see the Knowledge Base document In Unix, how do I change the permissions for a file?
Place the following line in a
.cshrc file to set the default
permissions for directories and files in your account:
Using this line, all new directories created in your account are given
a default protection of 755 (i.e., 777 - 022), which grants read,
write, and execute permission to the owner of the directory, and read
and execute permission to the group and others. New files created in
your account are given a default protection of 644 (i.e., 666 - 022),
which grants read and write permission to the owner of the file, and
read permission to the group and others.
|400||Read by owner|
|200||Write by owner|
|100||Execute by owner|
|040||Read by group|
|020||Write by group|
|010||Execute by group|
|004||Read by others|
|002||Write by others|
|001||Execute by others|
By default, most shells set the
umask to 022, giving you
write and read permissions, and others read permissions on
new directories and files. To determine what the current
is, at the Unix prompt, enter:
At Indiana University, for personal or departmental Linux or Unix systems support, see At IU, how do I get support for Linux or Unix?
Last modified on January 12, 2011.