tmpnam man page on Debian

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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
       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 3.27 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/.

				  2010-09-10			     TMPNAM(3)
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