MKSTEMP(3)

NAME
mkstemp - create a unique temporary file

SYNOPSIS
#include <stdlib.h>

int mkstemp(char *template);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

mkstemp(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
The mkstemp() function generates a unique temporary filename 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 open(2) O_EXCL flag, guaranteeing that when mkstemp() returns successfully we are the only user.

RETURN VALUE
On success, the mkstemp() function returns the file descriptor of the temporary file. On error, -1 is returned, and errno is set appropriately.

ERRORS

EEXIST
    Could not create a unique temporary filename. Now the contents of template are undefined.

EINVAL
    The last six characters of template were not XXXXXX. Now template is unchanged.

CONFORMING TO
4.3BSD, POSIX.1-2001

NOTES
The old behavior (creating a file with mode 0666) may be a security risk, especially since other Unix flavors 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(). The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows POSIX.1 and has the prototype in <stdlib.h>.

SEE ALSO
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)