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umask(2) [debian man page]

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

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 (i.e., only the file permission bits of mask are used), and returns the previous value of the mask. 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_IWGRP | 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. CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001. NOTES
A child process created via fork(2) inherits its parent's umask. The umask is left unchanged by execve(2). The umask setting also affects the permissions assigned to POSIX IPC objects (mq_open(3), sem_open(3), shm_open(3)), FIFOs (mkfifo(3)), and UNIX domain sockets (unix(7)) created by the process. The umask does not affect the permissions assigned to System V IPC objects created by the process (using msgget(2), semget(2), shmget(2)). SEE ALSO
chmod(2), mkdir(2), open(2), stat(2) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at Linux 2008-01-09 UMASK(2)

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UMASK(P)						     POSIX Programmer's Manual							  UMASK(P)

umask - set and get the file mode creation mask SYNOPSIS
#include <sys/stat.h> mode_t umask(mode_t cmask); DESCRIPTION
The umask() function shall set the process' file mode creation mask to cmask and return the previous value of the mask. Only the file per- mission bits of cmask (see <sys/stat.h>) are used; the meaning of the other bits is implementation-defined. The process' file mode creation mask is used during open(), creat(), mkdir(), and mkfifo() to turn off permission bits in the mode argument supplied. Bit positions that are set in cmask are cleared in the mode of the created file. RETURN VALUE
The file permission bits in the value returned by umask() shall be the previous value of the file mode creation mask. The state of any other bits in that value is unspecified, except that a subsequent call to umask() with the returned value as cmask shall leave the state of the mask the same as its state before the first call, including any unspecified use of those bits. ERRORS
No errors are defined. The following sections are informative. EXAMPLES
Unsigned argument and return types for umask() were proposed. The return type and the argument were both changed to mode_t. Historical implementations have made use of additional bits in cmask for their implementation-defined purposes. The addition of the text that the meaning of other bits of the field is implementation-defined permits these implementations to conform to this volume of IEEE Std 1003.1-2001. FUTURE DIRECTIONS
creat() , mkdir() , mkfifo() , open() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>, <sys/types.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at . IEEE
/The Open Group 2003 UMASK(P)
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