.\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 18:48:06 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Fri Jun 23 01:26:34 1995 by Andries Brouwer (aeb@cwi.nl)
.\" (prompted by Scott Burkett <scottb@IntNet.net>)
.\" Modified Sun Mar 28 23:44:38 1999 by Andries Brouwer (aeb@cwi.nl)
.\"
.TH MKTEMP 3  "April 3, 1993" "GNU" "Linux Programmer's Manual"
.SH NAME
mktemp \- make a unique temporary file name
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.sp
.BI "char *mktemp(char *" template );
.fi
.SH DESCRIPTION
The \fBmktemp()\fP function generates a unique temporary file name
from \fItemplate\fP.  The last six characters of \fItemplate\fP must
be XXXXXX and these are replaced with a string that makes the
filename unique. Since it will be modified,
.I template
must not be a string constant, but should be declared as a character array.
.SH "RETURN VALUE"
The \fBmktemp()\fP function returns NULL on error (\fItemplate\fP did not
end in XXXXXX) and \fItemplate\fP otherwise.
If the call was successful, the last six bytes of \fItemplate\fP will
have been modified in such a way that the resulting name is unique
(does not exist already). If the call was unsuccessful, \fItemplate\fP
is made an empty string.

.SH "ERRORS"
.TP
.B EINVAL
The last six characters of \fItemplate\fP were not XXXXXX.
.SH "CONFORMING TO"
BSD 4.3. POSIX dictates
.BR tmpnam (3).
.SH NOTE
The prototype is in
.I <unistd.h>
for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification
and has the prototype in
.IR <stdlib.h> .
.SH BUGS
Never use \fBmktemp()\fP. Some implementations follow BSD 4.3
and replace XXXXXX by the current process id and a single letter,
so that at most 26 different names can be returned.
Since on the one hand the names are easy to guess, and on the other
hand there is a race between testing whether the name exists and
opening the file, every use of \fBmktemp()\fP is a security risk.
The race is avoided by
.BR mkstemp (3).
.SH "SEE ALSO"
.BR mkstemp (3),
.BR tempnam (3),
.BR tmpfile (3),
.BR tmpnam (3)