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 de-
          fined 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 re-
          turns s.

          tempnam allows the user to control the choice of a directo-
          ry.  The argument dir points to the pathname of the directo-
          ry in which the file is to be created.  If dir is NULL or
          points to a string which is not a pathname for an appropri-
          ate directory, the pathname defined as p_tmpdir in the
          <stdio.h> header file is used.  If that pathname is not ac-
          cessible, /tmp will be used as a last resort.  This entire
          sequence can be upstaged by providing an environment vari-
          able 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 con-
          tain favorite initial letter sequences.  Use the pfx argu-
          ment 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 ex-
          pected result for any reason (i.e., malloc failed or at-
          tempts to find an appropriate directory were unsuccessful),
          a NULL pointer will be returned.





     April, 1990                                                     1

     tmpnam(3S)                                             tmpnam(3S)



     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).

     BUGS
          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 oth-
          er process is using tmpnam, tempnam, or mktemp(3C) and the
          filenames are chosen carefully to avoid duplication by other
          means.
































     2                                                     April, 1990