Provided by: manpages-dev_2.77-1_all
mkstemp - create a unique temporary file
int mkstemp(char *template);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
mkstemp(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500
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
On success, the mkstemp() function returns the file descriptor of the
temporary file. On error, -1 is returned, and errno is set
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.
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>.
Don’t use this function, use tmpfile(3) instead. It is better defined
and more portable.
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)
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