mkstemp - create a unique temporary file
int mkstemp(char *template);
function generates a unique temporary file name
. The last six characters of template
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,
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
returns successfully we are the only user.
function returns the file descriptor fd of the
temporary file or -1 on error.
The last six characters of template were not XXXXXX.
Now template is unchanged.
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 appropriately before calling
BSD 4.3, POSIX 1003.1-2001
The prototype is in
for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification
and has the prototype in
- RETURN VALUE
- CONFORMING TO
- SEE ALSO