umask | umask -S

 umask is a command that determines the settings of a mask that controls how file permissions are set for newly created files

The mask is stored as a group of bits. It may be represented as binary, octal or symbolic notation. The umask command allows the mask to be set as octal (e.g. 0754) or symbolic (e.g. u=,g=w,o=wx) notation.

$ umask         # display current value (as octal)
0022
$ umask -S      # display current value symbolically
u=rwx,g=rx,o=rx

$ umask 007    # set the mask to 007
$ umask        # display the mask (in octal)
0007           #   0 - special permissions (setuid | setgid | sticky )
               #   0 - (u)ser/owner part of mask
               #   0 - (g)roup part of mask
               #   7 - (o)thers/not-in-group part of mask
$ umask -S     # display the mask symbolically
u=rwx,g=rwx,o=

Letter	Class	Description
u	user	the owner
g	group	users who are members of the file's group
o	others	users who are not the owner of the file or members of the group
a	all	all three of the above, the same as ugo. (The default if no user-class-letters are specified in the maskExpression.)

• The operator specifies how the permission modes of the mask should be adjusted.

Operator	Effect on the mask
+	permissions specified are enabled, permissions that are not specified are unchanged.
-	permissions specified are prohibited from being enabled, permissions that are not specified are unchanged.
=	permissions specified are enabled, permissions that are not specified are prohibited from being enabled.

• The permission-symbols indicate which file permission settings are to be allowed or prohibited by the mask.

Symbol	Name	Description
r	read	read a file or list a directory's contents
w	write	write to a file or directory
x	execute	execute a file or recurse a directory tree
X	special execute	See Symbolic modes.
s	setuid/gid	See File permissions.
t	sticky	See File permissions.

Command line examples[edit]

Here are more examples of using the umask command to change the mask.

umask command issued	How the mask will affect permissions of subsequently created files/directories
umask a+r	allows read permission to be enabled for all user classes; the rest of the mask bits are unchanged
umask a-x	prohibits enabling execute permission for all user classes; the rest of the mask bits are unchanged
umask a+rw	allows read or write permission to be enabled for all user classes; the rest of the mask bits are unchanged
umask +rwx	allows read, write or execute permission to be enabled for all user classes; (Note: On some UNIX platforms, this will restore the mask to a default.)
umask u=rw,go=	allow read and write permission to be enabled for the owner, while prohibiting execute permission from being enabled for the owner; prohibit enabling any permissions for the group and others
umask u+w,go-w	allow write permission to be enabled for the owner; prohibit write permission from being enabled for the group and others;
umask -S	display the current umask in symbolic notation
umask 777	disallow read, write, and execute permission for all (probably not useful because even owner cannot read files created with this mask!)
umask 000	allow read, write, and execute permission for all (potential security risk)
umask 077	allow read, write, and execute permission for the file's owner, but prohibit read, write, and execute permission for everyone else
umask 113	allow read or write permission to be enabled for the owner and the group, but not execute permission; allow read permission to be enabled for others, but not write or execute permission
umask 0755	equivalent to u-rwx (4+2+1),go=w (4+1 & 4+1). (The 0 specifies that special modes[clarify] may be enabled if allowed by the OS.)