TMPNAM(3C) Standard C Library Functions TMPNAM(3C)
NAME
tmpnam, tmpnam_r, tempnam - create a name for a temporary file
SYNOPSIS
#include <stdio.h>
char *tmpnam(
char *s);
char *tmpnam_r(
char *s);
char *tempnam(
const char *dir,
const char *pfx);
DESCRIPTION
These functions generate file names that can be used safely for a
temporary file.
tmpnam() The
tmpnam() function always generates a file name using the path prefix
defined as
P_tmpdir in the <
stdio.h> header. On Solaris systems, the
default value for
P_tmpdir is
/var/tmp. If
s is
NULL,
tmpnam() leaves
its result in a thread-specific data area and returns a pointer to that
area. The next call to
tmpnam() by the same thread will destroy the
contents of the area. If
s is not
NULL, it is assumed to be the address
of an array of at least
L_tmpnam bytes, where
L_tmpnam is a constant
defined through inclusion of <
stdio.h>. The
tmpnam() function places its
result in that array and returns
s.
tmpnam_r() The
tmpnam_r() function has the same functionality as
tmpnam() except
that if
s is a null pointer, the function returns
NULL.
tempnam() The
tempnam() function allows the user to control the choice of a
directory. The argument
dir points to the name of the directory in which
the file is to be created. If
dir is
NULL or points to a string that is
not a name for an appropriate directory, the path prefix defined as
P_tmpdir in the <
stdio.h> header is used. If that directory is not
accessible,
/tmp is used. If, however, the
TMPDIR environment variable is
set in the user's environment, its value is used as the temporary-file
directory.
Many applications prefer that temporary files have certain initial
character sequences in their names. The
pfx argument may be
NULL or point
to a string of up to five characters to be used as the initial characters
of the temporary-file name.
Upon successful completion,
tempnam() uses
malloc(3C) to allocate space
for a string, puts the generated pathname in that space, and returns a
pointer to it. The pointer is suitable for use in a subsequent call to
free(). If
tempnam() cannot return the expected result for any reason
(for example,
malloc() failed), or if none of the above-mentioned
attempts to find an appropriate directory was successful, a null pointer
is returned and
errno is set to indicate the error.
ERRORS
The
tempnam() function will fail if:
ENOMEM Insufficient storage space is available.
USAGE
These functions generate a different file name each time they are called.
Files created using these functions and either
fopen(3C) or
creat(2) are
temporary only in the sense that they reside in a directory intended for
temporary use, and their names are unique. It is the user's
responsibility to remove the file when its use is ended.
If called more than
TMP_MAX (defined in <
stdio.h>) times in a single
process, these functions start recycling previously used names.
Between the time a file name is created and the file is opened, it is
possible for some other process to create a file with the same name. This
can never happen if that other process is using these functions or
mktemp(3C) and the file names are chosen to render duplication by other
means unlikely.
The
tmpnam() function is safe to use in multithreaded applications
because it employs thread-specific data if it is passed a NULL pointer.
However, its use is discouraged. The
tempnam() function is safe in
multithreaded applications and should be used instead.
When compiling multithreaded applications, the
_REENTRANT flag must be
defined on the compile line. This flag should be used only with
multithreaded applications.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+--------------------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+--------------------------------------+
|Interface Stability |
tmpnam() and
tempnam() are Standard. |
+--------------------+--------------------------------------+
|MT-Level | Safe |
+--------------------+--------------------------------------+
SEE ALSO
creat(2),
unlink(2),
fopen(3C),
free(3C),
malloc(3C),
mkstemp(3C),
mktemp(3C),
tmpfile(3C),
attributes(7),
standards(7) May 18, 2004
TMPNAM(3C)