NAME

       tempnam - create a name for a temporary file

SYNOPSIS

       #include <stdio.h>

       char *tempnam(const char *dir, const char *pfx);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       tempnam(): _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       The  tempnam() function returns a pointer to a string that is a valid filename, and such that a file with
       this name did not exist when tempnam() checked.  The filename suffix of the pathname generated will start
       with  pfx  in  case  pfx  is  a  non-NULL string of at most five bytes.  The directory prefix part of the
       pathname generated is required to be "appropriate" (often that at least implies writable).

       Attempts to find an appropriate directory go through the following steps:

       a) In case the environment variable TMPDIR exists and contains the name of an appropriate directory, that
          is used.

       b) Otherwise, if the dir argument is non-NULL and appropriate, it is used.

       c) Otherwise, P_tmpdir (as defined in <stdio.h>) is used when appropriate.

       d) Finally an implementation-defined directory may be used.

       The string returned by tempnam() is allocated using malloc(3) and hence should be freed by free(3).

RETURN VALUE

       On  success, the tempnam() function returns a pointer to a unique temporary filename.  It returns NULL if
       a unique name cannot be generated, with errno set to indicate the cause of the error.

ERRORS

       ENOMEM Allocation of storage failed.

CONFORMING TO

       SVr4, 4.3BSD, POSIX.1-2001.  POSIX.1-2008 marks tempnam() as obsolete.

NOTES

       Although tempnam() generates names that are difficult to guess, it is nevertheless possible that  between
       the time that tempnam() 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).

       SUSv2 does not mention the use of TMPDIR; glibc will use it only when the program is not set-user-ID.  On
       SVr4, the directory used under d) is /tmp (and this is what glibc does).

       Because  it  dynamically  allocates  memory used to return the pathname, tempnam() is reentrant, and thus
       thread safe, unlike tmpnam(3).

       The tempnam() function generates a different string each time it is called, up  to  TMP_MAX  (defined  in
       <stdio.h>) times.  If it is called more than TMP_MAX times, the behavior is implementation defined.

       tempnam() uses at most the first five bytes from pfx.

       The glibc implementation of tempnam() will fail with the error EEXIST upon failure to find a unique name.

BUGS

       The  precise meaning of "appropriate" is undefined; it is unspecified how accessibility of a directory is
       determined.

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

SEE ALSO

       mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3)

COLOPHON

       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the  project,  and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

                                                   2013-04-19                                         TEMPNAM(3)