tmpnam(3) Library Functions Manual tmpnam(3)
NAME
tmpnam, tmpnam_r - create a name for a temporary file
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#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
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 attrib-
utes(7).
┌──────────────────────────┬───────────────┬──────────────────────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────┼───────────────┼──────────────────────────┤
│ tmpnam() │ Thread safety │ MT-Unsafe race:tmpnam/!s │
├──────────────────────────┼───────────────┼──────────────────────────┤
│ tmpnam_r() │ Thread safety │ MT-Safe │
└──────────────────────────┴───────────────┴──────────────────────────┘
STANDARDS
tmpnam()
C11, POSIX.1-2008.
tmpnam_r()
None.
HISTORY
tmpnam()
SVr4, 4.3BSD, C89, POSIX.1-2001. Obsolete in POSIX.1-2008.
tmpnam_r()
Solaris.
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)
Linux man-pages 6.7 2023-10-31 tmpnam(3)
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