tmpnam, tmpnam_r - create a name for a temporary file
Standard C library (
libc,
-lc)
#include <stdio.h>
char *tmpnam(char *s);
char *tmpnam_r(char *s);
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(): SVr4, 4.3BSD, 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.
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)