UMASK(1) User Commands UMASK(1)


NAME


umask - get or set the file mode creation mask

SYNOPSIS


/usr/bin/umask [-S] [mask]


sh
umask [ooo]


csh
umask [ooo]


ksh
umask [-S] [mask]


ksh93
umask [-S] [mask]


DESCRIPTION


The umask utility sets the file mode creation mask of the current shell
execution environment to the value specified by the mask operand. This
mask affects the initial value of the file permission bits of
subsequently created files. If umask is called in a subshell or separate
utility execution environment, such as one of the following:

(umask 002)
nohup umask ...
find . -exec umask ...


it does not affect the file mode creation mask of the caller's
environment. For this reason, the /usr/bin/umask utility cannot be used
to change the umask in an ongoing session. Its usefulness is limited to
checking the caller's umask. To change the umask of an ongoing session
you must use one of the shell builtins.


If the mask operand is not specified, the umask utility writes the value
of the invoking process's file mode creation mask to standard output.

sh
The user file-creation mode mask is set to ooo. The three octal digits
refer to read/write/execute permissions for owner, group, and other,
respectively (see chmod(1), chmod(2), and umask(2)). The value of each
specified digit is subtracted from the corresponding ``digit'' specified
by the system for the creation of a file (see creat(2)). For example,
umask 022 removes write permission for group and other. Files (and
directories) normally created with mode 777 become mode 755. Files (and
directories) created with mode 666 become mode 644).

o If ooo is omitted, the current value of the mask is printed.

o umask is recognized and executed by the shell.

o umask can be included in the user's .profile (see profile(4))
and invoked at login to automatically set the user's
permissions on files or directories created.

csh
See the description above for the Bourne shell (sh)umask built-in.

ksh
The user file-creation mask is set to mask. mask can either be an octal
number or a symbolic value as described in chmod(1). If a symbolic value
is given, the new umask value is the complement of the result of applying
mask to the complement of the previous umask value. If mask is omitted,
the current value of the mask is printed.

ksh93
umask sets the file creation mask of the current shell execution
environment to the value specified by the mask operand. This mask affects
the file permission bits of subsequently created files. mask can either
be an octal number or a symbolic value as described in chmod(1). If a
symbolic value is specified, the new file creation mask is the complement
of the result of applying mask to the complement of the current file
creation mask. If mask is not specified, umask writes the value of the
file creation mask for the current process to standard output.

OPTIONS


ksh
The following option is supported for /usr/bin/umask and umask in ksh:

-S
Produces symbolic output.


The default output style is unspecified, but will be recognized on a
subsequent invocation of umask on the same system as a mask operand to
restore the previous file mode creation mask.

ksh93
The following option is supported in ksh93:

-S
Causes the file creation mask to be written or treated as a
symbolic value rather than an octal number.


OPERANDS


The following operand is supported:

mask
A string specifying the new file mode creation mask. The string
is treated in the same way as the mode operand described in the
chmod(1) manual page.

For a symbolic_mode value, the new value of the file mode
creation mask is the logical complement of the file permission
bits portion of the file mode specified by the symbolic_mode
string.

In a symbolic_mode value, the permissions op characters + and -
are interpreted relative to the current file mode creation mask.
+ causes the bits for the indicated permissions to be cleared in
the mask. - causes the bits of the indicated permissions to be
set in the mask.

The interpretation of mode values that specify file mode bits
other than the file permission bits is unspecified.

The file mode creation mask is set to the resulting numeric
value.

The default output of a prior invocation of umask on the same
system with no operand will also be recognized as a mask operand.
The use of an operand obtained in this way is not obsolescent,
even if it is an octal number.


OUTPUT


When the mask operand is not specified, the umask utility will write a
message to standard output that can later be used as a umask mask
operand.


If -S is specified, the message will be in the following format:

"u=%s,g=%s,o=%s\n", owner permissions, group permissions, \
other permissions


where the three values will be combinations of letters from the set {r,
w, x}. The presence of a letter will indicate that the corresponding bit
is clear in the file mode creation mask.


If a mask operand is specified, there will be no output written to
standard output.

EXAMPLES


Example 1: Using the umask Command




The examples in this section refer to the /usr/bin/umask utility and the
ksh umask builtin.


Either of the commands:


umask a=rx,ug+w
umask 002


sets the mode mask so that subsequently created files have their S_IWOTH
bit cleared.


After setting the mode mask with either of the above commands, the umask
command can be used to write the current value of the mode mask:


example$ umask
0002


The output format is unspecified, but historical implementations use the
obsolescent octal integer mode format.


example$ umask -S
u=rwx,g=rwx,o=rx


Either of these outputs can be used as the mask operand to a subsequent
invocation of the umask utility.


Assuming the mode mask is set as above, the command:


umask g-w


sets the mode mask so that subsequently created files have their S_IWGRP
and S_IWOTH bits cleared.


The command:


umask --w


sets the mode mask so that subsequently created files have all their
write bits cleared. Notice that mask operands r, w, x, or anything
beginning with a hyphen (-), must be preceded by - to keep it from being
interpreted as an option.


ENVIRONMENT VARIABLES


See environ(5) for descriptions of the following environment variables
that affect the execution of umask: LANG, LC_ALL, LC_COLLATELC_CTYPE,
LC_MESSAGES, and NLSPATH.

EXIT STATUS


The following exit values are returned:

0
The file mode creation mask was successfully changed, or no mask
operand was supplied.


>0
An error occurred.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:

/usr/bin/umask, csh, ksh, sh

+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

ksh93

+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | External |
+--------------------+-----------------+

SEE ALSO


chmod(1), csh(1), ksh(1), ksh93(1), sh(1), chmod(2), creat(2), umask(2),
profile(4), attributes(5), environ(5), standards(5)


September 17, 2007 UMASK(1)