umask() - Unix, Linux System Call
Tutorials Point


  Unix for Beginners
  Unix Shell Programming
  Advanced Unix
  Unix Useful References
  Unix Useful Resources
  Selected Reading

Copyright © 2014 by tutorialspoint



  Home     References     Discussion Forums     About TP  

umask() - Unix, Linux System Call


previous next AddThis Social Bookmark Button

Advertisements

NAME

umask - set file mode creation mask

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h> 

mode_t umask(mode_t mask);

DESCRIPTION

umask() sets the calling process’s file mode creation mask (umask) to mask & 0777.

The umask is used by open(2), mkdir(2), and other system calls that create files to modify the permissions placed on newly created files or directories. Specifically, permissions in the umask are turned off from the mode argument to open(2) and mkdir(2).

The constants that should be used to specify mask are described under stat(2).

The typical default value for the process umask is S_IWGRP | S_IWOTH (octal 022). In the usual case where the mode argument to open(2) is specified as:

S_IRUSR | S_IWUSR | S_IRGRP | S_IWRGRP | S_IROTH | S_IWOTH

(octal 0666) when creating a new file, the permissions on the resulting file will be:

S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH

(because 0666 & ~022 = 0644; i.e., rw-r--r--).

RETURN VALUE

This system call always succeeds and the previous value of the mask is returned.

NOTES

A child process created via fork(2) inherits its parent’s umask. The umask is left unchanged by execve(2).

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.

SEE ALSO



previous next Printer Friendly

Advertisements


  

Advertisements



Useful Video Courses


Video

Fundamentals of Unix and Linux System Administration

Best Seller

129 Lectures 23 hours

Eduonix Learning Solutions

Video

Essentials of Unix Operating System

5 Lectures 4.5 hours

Frahaan Hussain

Video

Unix Command Course for Beginners

35 Lectures 2 hours

Pradeep D

Video

Linux/Unix For DevOps and Developers

41 Lectures 2.5 hours

Musab Zayadneh

Video

Linux, Unix OS Command Line and Shell Scripting Introduction

46 Lectures 4 hours

GUHARAJANM

Video

Unix and Linux Training

6 Lectures 4 hours

Uplatz

Advertisements