UMASK(2) | 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), mkfifo(2) and mknod(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`() function is always successful.

# SEE ALSO

chmod(2), mkdir(2), mkfifo(2), mknod(2), open(2)

# STANDARDS

The `umask`() function conforms to IEEE Std 1003.1-1990 (“POSIX.1”).

June 4, 1993 | NetBSD 9.4