MKSTEMP(3) Linux Programmer's Manual MKSTEMP(3)
mkstemp - create a unique temporary file
int mkstemp(char *template);
The mkstemp() function generates a unique temporary file name from tem-
plate. 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.
The mkstemp() function returns the file descriptor fd of the temporary
file or -1 on error.
EINVAL The last six characters of template were not XXXXXX. Now tem-
plate is unchanged.
EEXIST Could not create a unique temporary filename. Now the contents
of template are undefined.
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 appro-
priately before calling mkstemp.
BSD 4.3, POSIX 1003.1-2001
The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows
the Single Unix Specification and has the prototype in <stdlib.h>.
mkdtemp(3), mktemp(3), tmpnam(3), tempnam(3), tmpfile(3)
GNU 2001-12-23 MKSTEMP(3)