NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON
TEMPNAM(3) Linux Programmer's Manual TEMPNAM(3)
tempnam - create a name for a temporary file
#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
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).
The tempnam() function returns a pointer to a unique temporary filename, or
NULL if a unique name cannot be generated.
ENOMEM Allocation of storage failed.
SVr4, 4.3BSD, POSIX.1-2001. POSIX.1-2008 marks tempnam() as obsolete.
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.
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.
mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3)
This page is part of release 3.23 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/.
2008-08-06 TEMPNAM(3)