tmpnam

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  gener-
       ated  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  charac-
       ter 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
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       +-----------+---------------+--------------------------+
       |Interface  | Attribute     | Value                    |
       +-----------+---------------+--------------------------+
       |tmpnam()   | Thread safety | MT-Unsafe race:tmpnam/!s |
       +-----------+---------------+--------------------------+
       |tmpnam_r() | Thread safety | MT-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  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 4.04 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/.

                                  2015-03-02                         TMPNAM(3)
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