TMPNAM(3)                           Linux Programmer's Manual                           TMPNAM(3)



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

SYNOPSIS
       #include <stdio.h>

       char *tmpnam(char *s);

DESCRIPTION
       Note: Avoid use of tmpnam(); use mkstemp(3) or tmpfile(3) instead.

       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  tmp‐
       nam().   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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The tmpnam() function is thread-safe with exceptions.  It is  not  thread-safe  if  called
       with a NULL parameter.

       The tmpnam_r() function is thread-safe.

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 sym‐
       bolic  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 pro‐
       totype 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 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



                                            2014-02-27                                  TMPNAM(3)