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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | BUGS | SEE ALSO | COLOPHON |
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tmpnam(3) Library Functions Manual tmpnam(3)
tmpnam, tmpnam_r - create a name for a temporary file
Standard C library (libc, -lc)
#include <stdio.h>
[[deprecated]] char *tmpnam(char *s);
[[deprecated]] 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
Note: avoid using these functions; use mkstemp(3) or tmpfile(3)
instead.
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 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.
These functions return a pointer to a unique temporary filename,
or NULL if a unique name cannot be generated.
No errors are defined.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────┬───────────────┬──────────────────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────┼───────────────┼──────────────────────────┤
│ tmpnam() │ Thread safety │ MT-Unsafe race:tmpnam/!s │
├─────────────────────┼───────────────┼──────────────────────────┤
│ tmpnam_r() │ Thread safety │ MT-Safe │
└─────────────────────┴───────────────┴──────────────────────────┘
tmpnam()
C11, POSIX.1-2008.
tmpnam_r()
None.
tmpnam()
SVr4, 4.3BSD, C89, POSIX.1-2001. Obsolete in POSIX.1-2008.
tmpnam_r()
Solaris.
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 returned 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.
Never use these functions. Use mkstemp(3) or tmpfile(3) instead.
mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 tmpnam(3)
Pages that refer to this page: getpid(2), mkdtemp(3), mkstemp(3), mktemp(3), stdio(3), tempnam(3), tmpfile(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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