Sets the default file-permission mask.
int _umask( int pmode );
| Routine | Required Header | Compatibility |
| _umask | <io.h> and <sys/stat.h> and <sys/types.h> | Win 95, Win NT |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
| LIBC.LIB | Single thread static library, retail version |
| LIBCMT.LIB | Multithread static library, retail version |
| MSVCRT.LIB | Import library for MSVCRT.DLL, retail version |
Return Value
_umask returns the previous value of pmode. There is no error return.
Parameter
pmode
Default permission setting
Remarks
The _umask function sets the file-permission mask of the current process to the mode specified by pmode. The file-permission mask modifies the permission setting of new files created by _creat, _open, or _sopen. If a bit in the mask is 1, the corresponding bit in the file’s requested permission value is set to 0 (disallowed). If a bit in the mask is 0, the corresponding bit is left unchanged. The permission setting for a new file is not set until the file is closed for the first time.
The argument pmode is a constant expression containing one or both of the manifest constants _S_IREAD and _S_IWRITE, defined in SYS\STAT.H. When both constants are given, they are joined with the bitwise-OR operator ( | ). If the pmode argument is _S_IREAD, reading is not allowed (the file is write-only). If the pmode argument is _S_IWRITE, writing is not allowed (the file is read-only). For example, if the write bit is set in the mask, any new files will be read-only. Note that with MS-DOS, Windows NT, and Windows 95, all files are readable; it is not possible to give write-only permission. Therefore, setting the read bit with _umask has no effect on the file’s modes.
Example
/* UMASK.C: This program uses _umask to set
* the file-permission mask so that all future
* files will be created as read-only files.
* It also displays the old mask.
*/
#include <sys/stat.h>
#include <sys/types.h>
#include <io.h>
#include <stdio.h>
void main( void )
{
int oldmask;
/* Create read-only files: */
oldmask = _umask( _S_IWRITE );
printf( "Oldmask = 0x%.4x\n", oldmask );
}
Output
Oldmask = 0x0000