UMASK(2FREEBSD) - man page online | system calls

Set file creation mode mask.

UMASK(2)                             BSD System Calls Manual                             UMASK(2)

NAME umask — set file creation mode mask
LIBRARY Standard C Library (libc, -lc)
SYNOPSIS #include <sys/stat.h> mode_t umask(mode_t numask);
DESCRIPTION The umask() routine sets the process's file mode creation mask to numask and returns the previous value of the mask. The 9 low-order access permission bits of numask are used by system calls, including open(2), mkdir(2), and mkfifo(2), to turn off corresponding bits requested in file mode. (See chmod(2)). This clearing allows each user to restrict the default access to his files. The default mask value is S_IWGRP|S_IWOTH (022, write access for the owner only). Child processes inherit the mask of the calling process.
RETURN VALUES The previous value of the file mode mask is returned by the call.
ERRORS The umask() system call is always successful.
SEE ALSO chmod(2), mkfifo(2), mknod(2), open(2)
STANDARDS The umask() system call is expected to conform to ISO/IEC 9945-1:1990 (“POSIX.1”).
HISTORY The umask() function appeared in Version 7 AT&T UNIX.
BSD June 4, 1993 BSD
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umask(2freebsd) referred by
refer to chmod(2) | mkdir(2) | mkfifo(2freebsd) | mknod(2) | open(2) | umask(2)