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NAME

       tmpnam, tmpnam_r - create a name for a temporary file

SYNOPSIS

       #include <stdio.h>

       char *tmpnam(char *s);

DESCRIPTION

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

RETURN VALUE

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

ERRORS

       No errors are defined.

CONFORMING TO

       SVr4, 4.3BSD, C89, C99, POSIX.1-2001.  POSIX.1-2008 marks tmpnam() as obsolete.

NOTES

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

       A POSIX draft proposed to use a function 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  from <stdio.h>, define _SVID_SOURCE or _BSD_SOURCE (before
       including any header file).

BUGS

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

SEE ALSO

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

COLOPHON

       This page is part of release 3.35 of the Linux man-pages project.  A  description  of  the
       project,  and information about reporting bugs, can be found at http://man7.org/linux/man-
       pages/.

                                            2010-09-10                                  TMPNAM(3)