1UMASK(2)                   Linux Programmer's Manual                  UMASK(2)
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NAME

6       umask - set file mode creation mask
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SYNOPSIS

9       #include <sys/types.h>
10       #include <sys/stat.h>
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12       mode_t umask(mode_t mask);
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DESCRIPTION

15       umask()  sets  the calling process's file mode creation mask (umask) to
16       mask & 0777.
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18       The umask is used by open(2), mkdir(2), and  other  system  calls  that
19       create files to modify the permissions placed on newly created files or
20       directories.  Specifically, permissions in the  umask  are  turned  off
21       from the mode argument to open(2) and mkdir(2).
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23       The  constants  that should be used to specify mask are described under
24       stat(2).
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26       The typical default value for the process  umask  is  S_IWGRP | S_IWOTH
27       (octal  022).   In the usual case where the mode argument to open(2) is
28       specified as:
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30           S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH
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32       (octal 0666) when creating a new file, the permissions on the resulting
33       file will be:
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35           S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH
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37       (because 0666 & ~022 = 0644; i.e., rw-r--r--).
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RETURN VALUE

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

44       A child process created via fork(2) inherits its parent's  umask.   The
45       umask is left unchanged by execve(2).
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CONFORMING TO

48       SVr4, 4.3BSD, POSIX.1-2001.
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SEE ALSO

51       chmod(2), mkdir(2), open(2), stat(2)
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55Linux                             2006-05-13                          UMASK(2)
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