TMPNAM(3S)                           BSD                            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)
     const char *dir, *pfx;

DESCRIPTION
     tmpnam generates file names that can safely be used for a temporary file.
     It always generates a filename using the path-prefix 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 name of the directory in which the file is to
     be created.  If dir is NULL, or points to a string that is not a valid
     directory name, the path-prefix defined as P_tmpdir in the stdio.h header
     file is used.  If that directory is not accessible, /tmp will be used as
     a last resort.  This entire sequence can be up-staged by providing an
     environment variable TMPDIR in the user's environment, whose value is the
     name of the desired temporary-file directory.

     Many applications prefer their temporary files to have certain favorite
     initial letter sequences in their names.  Use the pfx argument for this.
     This argument may be NULL, or point to a string of up to five characters
     to be used as the first few characters of the temporary-file name.

     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; that is, malloc(3C)
     failed, or none of the above mentioned attempts to find an appropriate
     directory was successful, a NULL, pointer is returned.

NOTES
     These calls generate a different filename each time it is called.

     Files created using tmpnam or tempnam 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), mktemp(3), tmpfile(3S).

CAVEATS
     If called more than TMP_MAX times in a single process, these calls start
     to recycle 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, and the file names are chosen to render duplication by other
     means unlikely.