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
The
tempnam()
function returns a pointer to a unique temporary
filename, or NULL if a unique name cannot be generated.
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.
This page is part of release 3.14 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/.
