MKSTEMP

NAME

mkstemp - create a unique temporary file

SYNOPSIS

#include <stdlib.h>

int mkstemp(char *template);

DESCRIPTION

The mkstemp() function generates a unique temporary file name from template. The last six characters of template must be XXXXXX and these are replaced with a string that makes the filename unique. The file is then created with mode read/write and permissions 0666 (glibc 2.0.6 and earlier), 0600 (glibc 2.0.7 and later). Since it will be modified, template must not be a string constant, but should be declared as a character array. The file is opened with the O_EXCL flag, guaranteeing that when mkstemp returns successfully we are the only user.

RETURN VALUE

The mkstemp() function returns the file descriptor fd of the temporary file or -1 on error.

ERRORS

EINVAL: The last six characters of template were not XXXXXX. Now template is unchanged.
EEXIST: Could not create a unique temporary filename. Now the contents of template are undefined.

NOTES

The old behaviour (creating a file with mode 0666) may be a security risk, especially since other Unix flavours use 0600, and somebody might overlook this detail when porting programs.

More generally, the POSIX specification does not say anything about file modes, so the application should make sure its umask is set appropriately before calling mkstemp.

CONFORMING TO

BSD 4.3, POSIX 1003.1-2001

NOTE

The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification and has the prototype in <stdlib.h>.