tmpnam, tmpnam_r — create a name for a temporary file
#include <stdio.h>
char
*tmpnam( |
char *s); |
The tmpnam() function
returns a pointer to a string that is a valid filename, and
such that a file with this name did not exist at some point
in time, so that naive programmers may think it a suitable
name for a temporary file. If the argument s is NULL this name is
generated in an internal static buffer and may be overwritten
by the next call to tmpnam().
If s is not NULL, the
name is copied to the character array (of length at least
L_tmpnam) pointed to by
s and the value
s is returned in case
of success.
The pathname that is created, has a directory prefix
P_tmpdir. (Both L_tmpnam and P_tmpdir are defined in <stdio.h>
just like the TMP_MAX mentioned
below.)
The tmpnam() function
returns a pointer to a unique temporary filename, or NULL if
a unique name cannot be generated.
The tmpnam() function
generates a different string each time it is called, up to
TMP_MAX times. If it is called
more than TMP_MAX times, the
behavior is implementation defined.
Although tmpnam() generates
names that are difficult to guess, it is nevertheless
possible that between the time that tmpnam() returns a pathname, and the time
that the program opens it, another program might create that
pathname using open(2), or create it as a
symbolic link. This can lead to security holes. To avoid such
possibilities, use the open(2) O_EXCL flag to open the pathname. Or better
yet, use mkstemp(3) or tmpfile(3).
Portable applications that use threads cannot call
tmpnam() with a NULL argument
if either _POSIX_THREADS or
_POSIX_THREAD_SAFE_FUNCTIONS is
defined.
A POSIX draft proposed to use a function tmpnam_r() defined by
char * tmpnam_r(char *s) { return s ? tmpnam(s) : NULL; }
apparently as a warning not to use NULL. A few systems
implement it. To get a glibc prototype for this function from
<stdio.h>
define _SVID_SOURCE or
_BSD_SOURCE (before including
any header file).
This page is part of release 3.33 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
|
Copyright (c) 1999 Andries Brouwer (aebcwi.nl) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. 2003-11-15, aeb, added tmpnam_r |