tmpnam, tmpnam_r, tempnam - create a name for a temporary
char *tmpnam(char *s);
char *tmpnam_r(char *s);
char *tempnam(const char *dir, const char *pfx);
These functions generate file names that can be used safely
for a temporary file.
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 an
internal static area and returns a pointer to that area. The
next call to tmpnam() 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 con-
stant defined in <stdio.h>; tmpnam() places its result in
that array and returns s.
The tmpnam_r() function has the same functionality as
tmpnam() except that if s is a null pointer, the function
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 accessi-
ble, /tmp is used. If, however, the TMPDIR environment vari-
able 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
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 temp-
nam() 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
The tempnam() function will fail if:
Insufficient storage space is available.
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
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
The tmpnam() function is unsafe in multithreaded applica-
tions. 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.
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | See USAGE above. |
creat(2), unlink(2), fopen(3C), free(3C), malloc(3C),
mktemp(3C), tmpfile(3C), attributes(5)
Man(1) output converted with