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TMPFILE(3)		 BSD Library Functions Manual		    TMPFILE(3)

     tempnam, tmpfile, tmpnam -- temporary file	routines

     Standard C	Library	(libc, -lc)

     #include <stdio.h>

     FILE *

     char *
     tmpnam(char *str);

     char *
     tempnam(const char	*tmpdir, const char *prefix);

     The tmpfile() function returns a pointer to a stream associated with a
     file descriptor returned by the routine mkstemp(3).  The created file is
     unlinked before tmpfile() returns,	causing	the file to be automatically
     deleted when the last reference to	it is closed.  The file	is opened with
     the access	value `w+'.  The file is created in the	directory determined
     by	the environment	variable TMPDIR	if set.	 The default location if
     TMPDIR is not set is /tmp.

     The tmpnam() function returns a pointer to	a file name, in	the P_tmpdir
     directory,	which did not reference	an existing file at some indeterminate
     point in the past.	 P_tmpdir is defined in	the include file <stdio.h>.
     If	the argument str is non-NULL, the file name is copied to the buffer it
     references.  Otherwise, the file name is copied to	a static buffer.  In
     either case, tmpnam() returns a pointer to	the file name.

     The buffer	referenced by str is expected to be at least L_tmpnam bytes in
     length.  L_tmpnam is defined in the include file <stdio.h>.

     The tempnam() function is similar to tmpnam(), but	provides the ability
     to	specify	the directory which will contain the temporary file and	the
     file name prefix.

     The environment variable TMPDIR (if set), the argument tmpdir (if
     non-NULL),	the directory P_tmpdir,	and the	directory /tmp are tried, in
     the listed	order, as directories in which to store	the temporary file.

     The argument prefix, if non-NULL, is used to specify a file name prefix,
     which will	be the first part of the created file name.  Tempnam() allo-
     cates memory in which to store the	file name; the returned	pointer	may be
     used as a subsequent argument to free(3).

     The tmpfile() function returns a pointer to an open file stream on	suc-
     cess, and a NULL pointer on error.

     The tmpnam() and tempfile() functions return a pointer to a file name on
     success, and a NULL pointer on error.

     The tmpfile() function may	fail and set the global	variable errno for any
     of	the errors specified for the library functions fdopen(3) or

     The tmpnam() function may fail and	set errno for any of the errors	speci-
     fied for the library function mktemp(3).

     The tempnam() function may	fail and set errno for any of the errors spec-
     ified for the library functions malloc(3) or mktemp(3).

     mkstemp(3), mktemp(3)

     The tmpfile() and tmpnam()	functions conform to ISO/IEC 9899:1990
     ("ISO C90").

     These interfaces are provided for System V	and ANSI compatibility only.
     The mkstemp(3) interface is strongly preferred.

     There are four important problems with these interfaces (as well as with
     the historic mktemp(3) interface).	 First,	there is an obvious race be-
     tween file	name selection and file	creation and deletion.	Second,	most
     historic implementations provide only a limited number of possible	tempo-
     rary file names (usually 26) before file names will start being recycled.
     Third, the	System V implementations of these functions (and of mktemp(3))
     use the access(2) function	to determine whether or	not the	temporary file
     may be created.  This has obvious ramifications for setuid	or setgid pro-
     grams, complicating the portable use of these interfaces in such pro-
     grams.  Finally, there is no specification	of the permissions with	which
     the temporary files are created.

     This implementation does not have these flaws, but	portable software can-
     not depend	on that.  In particular, the tmpfile() interface should	not be
     used in software expected to be used on other systems if there is any
     possibility that the user does not	wish the temporary file	to be publicly
     readable and writable.

BSD			       November	17, 1993			   BSD


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