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



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():
	   Since glibc 2.19:
	       _DEFAULT_SOURCE
	   Glibc 2.19 and earlier:
	       _BSD_SOURCE || _SVID_SOURCE

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

       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	 temp-
       nam()  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 appropri-
	  ate.

       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 tempo-
       rary 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.

ATTRIBUTES
       For   an	  explanation	of   the  terms	 used  in  this	 section,  see
       attributes(7).

       +----------+---------------+-------------+
       |Interface | Attribute	  | Value	|
       +----------+---------------+-------------+
       |tempnam() | Thread safety | MT-Safe env |
       +----------+---------------+-------------+
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.

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

COLOPHON
       This  page  is  part of release 4.10 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
       https://www.kernel.org/doc/man-pages/.



				  2016-03-15			    TEMPNAM(3)