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.TH UMASK 1 "Sep 17, 2007"
.SH NAME
umask \- get or set the file mode creation mask
.SH SYNOPSIS
.LP
.nf
\fB/usr/bin/umask\fR [\fB-S\fR] [\fImask\fR]
.fi

.SS "sh"
.LP
.nf
\fBumask\fR [\fIooo\fR]
.fi

.SS "csh"
.LP
.nf
\fBumask\fR [\fIooo\fR]
.fi

.SS "ksh"
.LP
.nf
\fBumask\fR [\fB-S\fR] [\fImask\fR]
.fi

.SS "ksh93"
.LP
.nf
\fBumask\fR [\fB-S\fR] [\fImask\fR]
.fi

.SH DESCRIPTION
.sp
.LP
The \fBumask\fR utility sets the file mode creation mask of the current shell
execution environment to the value specified by the \fImask\fR operand. This
mask affects the initial value of the file permission bits of subsequently
created files. If \fBumask\fR is called in a subshell or separate utility
execution environment, such as one of the following:
.sp
.in +2
.nf
(umask 002)
nohup umask ...
find . -exec umask ...
.fi
.in -2
.sp

.sp
.LP
it does not affect the file mode creation mask of the caller's environment. For
this reason, the \fB/usr/bin/umask\fR 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.
.sp
.LP
If the \fImask\fR operand is not specified, the \fBumask\fR utility writes the
value of the invoking process's file mode creation mask to standard output.
.SS "sh"
.sp
.LP
The user file-creation mode mask is set to \fIooo\fR. The three octal digits
refer to read/write/execute permissions for owner, group, and other,
respectively (see \fBchmod\fR(1), \fBchmod\fR(2), and \fBumask\fR(2)). The
value of each specified digit is subtracted from the corresponding ``digit''
specified by the system for the creation of a file (see \fBcreat\fR(2)). For
example, \fBumask\fR \fB022\fR removes write permission for group and other.
Files (and directories) normally created with mode \fB777\fR become mode
\fB755\fR. Files (and directories) created with mode \fB666\fR become mode
\fB644\fR).
.RS +4
.TP
.ie t \(bu
.el o
If \fIooo\fR is omitted, the current value of the mask is printed.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBumask\fR is recognized and executed by the shell.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBumask\fR can be included in the user's \fB\&.profile\fR (see
\fBprofile\fR(4)) and invoked at login to automatically set the user's
permissions on files or directories created.
.RE
.SS "csh"
.sp
.LP
See the description above for the Bourne shell (\fBsh\fR)\fBumask\fR built-in.
.SS "ksh"
.sp
.LP
The user file-creation mask is set to \fImask\fR. \fImask\fR can either be an
octal number or a symbolic value as described in \fBchmod\fR(1). If a symbolic
value is given, the new \fBumask\fR value is the complement of the result of
applying \fImask\fR to the complement of the previous umask value. If
\fImask\fR is omitted, the current value of the mask is printed.
.SS "ksh93"
.sp
.LP
\fBumask\fR sets the file creation mask of the current shell execution
environment to the value specified by the \fBmask\fI\fR\fR operand. This mask
affects the file permission bits of subsequently created files. \fImask\fR 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 \fImask\fR to the complement of the current file
creation mask. If \fImask\fR is not specified, \fBumask\fR writes the value of
the file creation mask for the current process to standard output.
.SH OPTIONS
.SS "ksh"
.sp
.LP
The following option is supported for \fB/usr/bin/umask\fR and \fBumask\fR in
\fBksh\fR:
.sp
.ne 2
.na
\fB\fB-S\fR\fR
.ad
.RS 6n
Produces symbolic output.
.RE

.sp
.LP
The default output style is unspecified, but will be recognized on a subsequent
invocation of \fBumask\fR on the same system as a \fImask\fR operand to restore
the previous file mode creation mask.
.SS "ksh93"
.sp
.LP
The following option is supported in \fBksh93\fR:
.sp
.ne 2
.na
\fB\fB-S\fR\fR
.ad
.RS 6n
Causes the file creation mask to be written or treated as a symbolic value
rather than an octal number.
.RE

.SH OPERANDS
.sp
.LP
The following operand is supported:
.sp
.ne 2
.na
\fB\fImask\fR\fR
.ad
.RS 8n
A string specifying the new file mode creation mask. The string is treated in
the same way as the \fImode\fR operand described in the \fBchmod\fR(1) manual
page.
.sp
For a \fIsymbolic_mode\fR 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 \fIsymbolic_mode\fR string.
.sp
In a \fIsymbolic_mode\fR value, the permissions \fIop\fR characters \fB+\fR and
\fB\(mi\fR are interpreted relative to the current file mode creation mask.
\fB+\fR causes the bits for the indicated permissions to be cleared in the
mask. \fB\(mi\fR causes the bits of the indicated permissions to be set in the
mask.
.sp
The interpretation of \fImode\fR values that specify file mode bits other than
the file permission bits is unspecified.
.sp
The file mode creation mask is set to the resulting numeric value.
.sp
The default output of a prior invocation of \fBumask\fR on the same system with
no operand will also be recognized as a \fImask\fR operand. The use of an
operand obtained in this way is not obsolescent, even if it is an octal number.
.RE

.SH OUTPUT
.sp
.LP
When the \fImask\fR operand is not specified, the \fBumask\fR utility will
write a message to standard output that can later be used as a \fBumask\fR
\fImask\fR operand.
.sp
.LP
If \fB-S\fR is specified, the message will be in the following format:
.sp
.in +2
.nf
"u=%s,g=%s,o=%s\en", \fIowner permissions\fR, \fIgroup permissions\fR, \e
                        \fIother permissions\fR
.fi
.in -2
.sp

.sp
.LP
where the three values will be combinations of letters from the set
\fB{\fRr\fB,\fR \fBw\fR, \fBx\fR}. The presence of a letter will indicate that
the corresponding bit is clear in the file mode creation mask.
.sp
.LP
If a \fImask\fR operand is specified, there will be no output written to
standard output.
.SH EXAMPLES
.LP
\fBExample 1 \fRUsing the \fBumask\fR Command
.sp
.LP
The examples in this section refer to the \fB/usr/bin/umask\fR utility and the
\fBksh umask\fR builtin.

.sp
.LP
Either of the commands:

.sp
.in +2
.nf
\fBumask a=rx,ug+w
umask 002\fR
.fi
.in -2
.sp

.sp
.LP
sets the mode mask so that subsequently created files have their \fBS_IWOTH\fR
bit cleared.

.sp
.LP
After setting the mode mask with either of the above commands, the \fBumask\fR
command can be used to write the current value of the mode mask:

.sp
.in +2
.nf
example$ \fBumask\fR
0002
.fi
.in -2
.sp

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

.sp
.in +2
.nf
example$ \fBumask -S\fR
u=rwx,g=rwx,o=rx
.fi
.in -2
.sp

.sp
.LP
Either of these outputs can be used as the mask operand to a subsequent
invocation of the \fBumask\fR utility.

.sp
.LP
Assuming the mode mask is set as above, the command:

.sp
.in +2
.nf
\fBumask g-w\fR
.fi
.in -2
.sp

.sp
.LP
sets the mode mask so that subsequently created files have their \fBS_IWGRP\fR
and \fBS_IWOTH\fR bits cleared.

.sp
.LP
The command:

.sp
.in +2
.nf
\fBumask --w\fR
.fi
.in -2
.sp

.sp
.LP
sets the mode mask so that subsequently created files have all their write bits
cleared. Notice that \fImask\fR operands \fBr\fR, \fBw\fR, \fBx\fR, or anything
beginning with a hyphen (\fB\(mi\fR), must be preceded by \fB-\fR to keep it
from being interpreted as an option.

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBumask\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_COLLATE\fR\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
The file mode creation mask was successfully changed, or no \fImask\fR operand
was supplied.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.RS 6n
An error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.SS "/usr/bin/umask, csh, ksh, sh"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SS "ksh93"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	External
.TE

.SH SEE ALSO
.sp
.LP
\fBchmod\fR(1), \fBcsh\fR(1), \fBksh\fR(1), \fBksh93\fR(1), \fBsh\fR(1),
\fBchmod\fR(2), \fBcreat\fR(2), \fBumask\fR(2), \fBprofile\fR(4),
\fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)