tmpnam, tmpnam_r - create a name for a temporary file

#include <stdio.h>
 I char *tmpnam(char * s );

The R 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 R tmpnam (). If s is not NULL, the name is copied to the character array (of length at least R 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 R P_tmpdir . (Both L_tmpnam and P_tmpdir are defined in R <stdio.h> , just like the TMP_MAX mentioned below.)

The R tmpnam () function returns a pointer to a unique temporary filename, or NULL if a unique name cannot be generated.

No errors are defined.

SVr4, 4.3BSD, C89, C99, POSIX.1-2001.

The R 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(3) generates names that are difficult to guess, it is nevertheless possible that between the time that tmpnam(3) 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 R tmpnam () with NULL parameter if either _POSIX_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is defined.

A POSIX draft proposed to use a function R 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, define _SVID_SOURCE or _BSD_SOURCE before including R <stdio.h> .

Never use this function. Use mkstemp(3) or tmpfile(3) instead.

mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)