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(5))
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(7) 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(7) 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(5),
attributes(7),
environ(7),
standards(7) September 17, 2007
UMASK(1)