tmpnam(3S)                                             tmpnam(3S)



NAME
     tmpnam, tempnam - create a name for a temporary file

SYNOPSIS
     #include <stdio.h>

     char *tmpnam(s)
     char *s;

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

DESCRIPTION
     These functions generate filenames that can safely be used
     for a temporary file.

     tmpnam always generates a filename using the pathname
     defined as p_tmpdir in the <stdio.h> header file.  If s is
     NULL, tmpnam leaves its result in an internal static area
     and returns a pointer to that area.  The next call to tmpnam
     will destroy the contents of the area.  If s is not NULL, it
     is assumed to be the address of an array of at least
     l_tmpnam bytes, where l_tmpnam is a constant defined in
     <stdio.h>; tmpnam places its result in that array and
     returns s.

     tempnam allows the user to control the choice of a
     directory.  The argument dir points to the pathname of the
     directory in which the file is to be created.  If dir is
     NULL or points to a string that is not a pathname for an
     appropriate directory, the pathname defined as p_tmpdir in
     the <stdio.h> header file is used.  If that pathname is not
     accessible, /tmp will be used as a last resort.  This entire
     sequence can be upstaged by providing an environment
     variable TMPDIR in the user's environment, whose value is a
     pathname for the desired temporary-file directory.

     Many applications prefer that names of temporary files
     contain favorite initial letter sequences.  Use the pfx
     argument for this.  This argument may be NULL or point to a
     string of up to 5 characters to be used as the first few
     characters of the name of the temporary file.

     tempnam uses malloc(3C) to get space for the constructed
     filename and returns a pointer to this area.  Thus, any
     pointer value returned from tempnam may serve as an argument
     to free (see malloc(3C)).  If tempnam cannot return the
     expected result for any reason (such as malloc failed or
     attempts to find an appropriate directory were
     unsuccessful), a NULL pointer will be returned.





January 1992                                                    1

tmpnam(3S)                                             tmpnam(3S)



LIMITATIONS
     If called more than 17,576 times in a single process, tmpnam
     and tempnam will start recycling previously used names.
     Between the time a filename is created and the file is
     opened, it is possible for some other process to create a
     file with the same name.  This can never happen if that
     other process is using tmpnam, tempnam, or mktemp(3C) and
     the filenames are chosen carefully to avoid duplication by
     other means.

NOTES
     These functions generate a different filename each time they
     are called.

     Files created using these functions and either fopen(3S) or
     creat(2) are temporary only in the sense that they reside in
     a directory intended for temporary use and their names are
     unique.  It is the user's responsibility to use unlink(2) to
     remove the file when its use is ended.

SEE ALSO
     creat(2), unlink(2), fopen(3S), malloc(3C), mktemp(3C),
     tmpfile(3S)
































2                                                    January 1992