HPUX umask[1]
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umask.2
umask(1) umask(1)
NAME
umask - get or set the file mode creation mask
SYNOPSIS
Get Mask:
umask [-S]
Set Mask:
umask [mask]
DESCRIPTION
umask is a built-in shell command (executed within the shell process)
that can be used to print the current file mode creation mask value or
to set a new one.
When a new file is created, each bit in the file mode creation mask
that is set causes the corresponding permission bit in the the file
mode to be cleared (disabled); hence the term mask. Conversely, bits
that are cleared in the mask allow the corresponding file mode bits to
be enabled in newly created files.
Getting Current Mask Value
To print the current file mode creation mask value, use one of the
commands:
umask Print the octal value of the current file mode
creation mask.
umask -S Print the current file mode creation mask value
using a symbolic format that resembles:
u=rwx,g=rwx,o=rwx
where zero, one, two, or three of the letters r,
w, and x are printed for each category: u (user
(or owner)), g (group), and o (other), depending
on the current mask setting. Each r, w, or x in
the output indicates that the corresponding
permissions are allowed in newly created files.
Both command-line forms produce output that is a valid value for use
as the mask argument in a subsequent umask command when setting a new
mask value.
Note that the -S option is implemented only in the Korn shell (see
ksh(1)) and in the POSIX shell (see sh-posix(1)). Other shells such
as Bourne shell (see sh-bourne(1)) and C shell (see csh(1)) do not
support the symbolic output form.
Setting A New Mask Value
To set a new file mode creation mask value for the current shell
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execution environment, use the command:
umask mask
where mask can be a symbolic value or a non-negative octal integer
(obsolescent). The resulting interpreted mask affects the initial
value of the file permission bits for subsequently created files.
Symbolic mask Value:
The umask command built into the POSIX and Korn shells accepts
symbolic mask values (as well as the obsolescent octal form).
Symbolic mask values are constructed in the same manner as when using
the chmod command (see chmod(1)) by concatenating comma-separated
strings of the form:
who operator permissions
constructed as follows:
who One of the characters or character combinations u, g,
o, ug, uo, go, ugo, or a (short form for ugo). If who
is not specified, the operator and permissions apply to
all categories. If two or more who categories have the
same mask value, they can be placed together by using
ug, uo, go, ugo, or a as appropriate.
If who is omitted, operator and permissions apply to
all categories (same as a or ugo).
operator One of the characters +, -, or =. An operator is
required for each who. Multiple operations can be
performed on a given who in a complete mask argument,
such as when permissions are deleted from all or some
categories then new permissions are added by another
mask substring (see EXAMPLES below).
If no permissions are specified for a given operator,
no change is made to the current file creation mode
mask. If who is not specified, the operation applies
to all categories (u, g, and o).
operators are interpreted as follows:
+ Clear the file mode bits represented by
the accompanying who and permissions
values in the mask, thus enabling
corresponding permissions in newly created
files.
- Set the file mode bits represented by the
specified who and permissions values in
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the mask, thus denying corresponding
permissions in newly created files.
= Clear the file mode bits specified by the
corresponding who and permissions values
and set all others.
permissions
One of the characters or character combinations r, w,
x, rx, wx, rw, or rwx, specifying read, write, and/or
execute (search) permission for the corresponding who
and operator.
If permissions is not specified, no change is made to
the existing file creation mode mask for the
corresponding who.
Octal mask Value (obsolescent):
The umask command built into the POSIX, Korn, C, and Bourne
shells accepts a non-negative integer value for mask. For an
octal integer mask operand, the file mode bits are set
absolutely.
If the user file-creation mode mask value is specified as three
octal digits, they refer to read/write/execute permissions for
owner, group, and others, respectively (see 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, the command
umask 022 removes group and others write permission (files
normally created with mode 777 become mode 755; files created
with mode 666 become mode 644).
The following table gives the octal integers and the
corresponding mode-bits:
center box tab(;); cBss | cBss
| cBss cB | cB | cB | cB | cB | cB | cB
| cB | cB cf4p+1 | cf4p+1 | cf4p+1 | cf4p+1 | cf4p+1 | cf4p+1
| cf4p+1 | cf4p+1 | cf4p+1. User;Group;Other _
Symbolic;Octal;Mode bit;Symbolic;Octal;Mode
bit;Symbolic;Octal;Mode bit _
u+r;0400;S_IRUSR;g+r;0040;S_IRGRP;o+r;0004;S_IROTH
u+w;0200;S_IWUSR;g+w;0020;S_IWGRP;o+w;0002;S_IWOTH
u+x;0100;S_IXUSR;g+x;0010;S_IXGRP;o+x;0001;S_IXOTH
If mask is omitted, the current value of the mask is printed in
octal. The first digit, a zero, specifies that the output is
expressed in octal. umask writes a message to standard output
that can be later used as a umask mask operand. The use of an
operand obtained in this way is not obsolescent, even if it is an
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octal number.
If a mask operand is specified, there is no output written to
standard output.
umask is recognized and executed by the shell.
Note that the file creation mode mask does not affect the set-
user-ID, set-group-ID, or ``sticky'' bits.
Since umask affects the current shell execution environment, it
is generally provided as a shell regular built-in. Moreover,
different shells provide different implementations of umask as a
built-in. Features of umask as described here may not be
supported by all the shells. Refer to the manual entry for
specific shells for differences.
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.
RETURN VALUE
umask exits with one of the following values:
0 The file mode creation mask was successfully
changed or no mask operand was supplied.
>0 An error occurred.
EXAMPLES
Symbolic-Mode:
Set the umask value to produce read, write, and execute permissions
for the file's owner and read-only permission for all others (-rwxr--
r--) on newly created files:
umask u=rwx,g=r,o=r
Set the umask value to produce read, and write permissions for the
file's owner, read-only for others users in the same group, and no
access to others (-rw-r-----):
umask a-rwx,u+rw,g+r
Octal-Mode:
Set the umask value to deny read, write, or execute permissions to
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everyone (----------):
umask 0777
SEE ALSO
chmod(1), csh(1), ksh(1), sh-posix(1), sh(1), chmod(2), creat(2),
umask(2).
STANDARDS CONFORMANCE
umask: SVID2, XPG2, XPG3, POSIX.2
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