V7/usr/man/man2/umask.2

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.TH UMASK 2
.SH NAME
umask \- set file creation mode mask
.SH SYNOPSIS
.B umask(complmode)
.SH DESCRIPTION
.I Umask
sets a mask used whenever a file is created by
.IR creat (2)
or
.IR mknod (2):
the actual mode (see
.IR chmod (2))
of the newly-created file is the logical
.B and
of the given mode and the complement of the argument.
Only the low-order 9 bits of the mask (the protection bits)
participate.
In other words, the mask shows the bits to be turned off
when files are created.
.PP
The previous value of the mask is returned by the call.
The value is initially 0 (no restrictions).
The mask is inherited by child processes.
.SH SEE ALSO
creat(2), mknod(2), chmod(2)
.SH ASSEMBLER
(umask = 60.)
.br
.B sys umask; complmode