tmpnam
TMPNAM(3) Linux Programmer's Manual TMPNAM(3)
NAME
tmpnam, tmpnam_r - create a name for a temporary file
SYNOPSIS
#include <stdio.h>
char *tmpnam(char *s);
char *tmpnam_r(char *s);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
tmpnam_r()
Since glibc 2.19:
_DEFAULT_SOURCE
Up to and including glibc 2.19:
_BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
Note: avoid using these functions; use mkstemp(3) or tmpfile(3) in-
stead.
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 gener-
ated 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 charac-
ter array (of length at least L_tmpnam) pointed to by s and the value s
is returned in case of success.
The created pathname 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_r() function performs the same task as tmpnam(), but returns
NULL (to indicate an error) if s is NULL.
RETURN VALUE
These functions return a pointer to a unique temporary filename, or
NULL if a unique name cannot be generated.
ERRORS
No errors are defined.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
+-----------+---------------+--------------------------+
|Interface | Attribute | Value |
+-----------+---------------+--------------------------+
|tmpnam() | Thread safety | MT-Unsafe race:tmpnam/!s |
+-----------+---------------+--------------------------+
|tmpnam_r() | Thread safety | MT-Safe |
+-----------+---------------+--------------------------+
CONFORMING TO
tmpnam(): SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX.1-2008 marks
tmpnam() as obsolete.
tmpnam_r() is a nonstandard extension that is also available on a few
other systems.
NOTES
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 these functions generate names that are difficult to guess, it
is nevertheless possible that between the time that the pathname is re-
turned 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 mk-
stemp(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.
BUGS
Never use these functions. Use mkstemp(3) or tmpfile(3) instead.
SEE ALSO
mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)
COLOPHON
This page is part of release 5.05 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2017-09-15 TMPNAM(3)
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