tempnam()

NAME

tempnam() - temporary file routine

SYNOPSIS 

#include <stdio.h>


char * tempnam (const char *dir, char *pfx)

DESCRIPTION

The tempnam(3) function is similar to tmpnam(3) in that it returns a pointer to a pathname of a file that does not exist at the time of the call. Unlike tmpnam(3), you can specify the directory that will contain the file (dir) if there is no defined temporary directory, and you can specify the filename's prefix, (pfx).

The tempnam(3) function also looks to use different directories by default than does tmpnam(3). It determines the directory for the file using the following steps:

  1. The directory used is the directory defined by TMPDIR if it is writeable.
  2. If the previous step does not produce a usable directory, then the directory used is the directory specified by the dir argument if it exists and is writeable.
  3. If the previous step does not produce a usable directory, then the directory used is the directory specified by P_tmpdir as declared in stdio.h if it exists and is writeable.
  4. If the previous step does not produce a usable directory, then the function attempts to use /tmp.

The argument pfx, if non-NULL, is used to specify a file name prefix, which will be the first part of the created file name. The pfx can be up to five characters long.

Tempnam(3) allocates space for the string; the pointer can be used in a call to free(3).

RETURN VALUES

The tempnam(3) function returns a pointer to a file name on success, and a NULL pointer on error.

ERRORS

The tempnam(3) function may fail and set the global variable errno for this reason:

[ENOMEM]
There isn't enough memory.

NOTES

Using tempnam(3) is discouraged for these reasons:

  1. There can be a race between file name selection and file name creation.
  2. There is no specification for the minimum number of unique temporary names; some implementations generate as few as 26 before recycling.
  3. Some implementations use access(2) to determine whether the temp file may be created. this can cause problems for use with setuid(2) and setgid(2) programs.

SEE ALSO

mktemp(3)

tmpfile(3)