tmpnam(3s)tmpnam(3s)Name
tmpnam, tempnam - create a name for a temporary file
Syntax
#include <stdio.h>
char ∗tmpnam (s)
char ∗s;
char ∗tempnam (dir, pfx)
char ∗dir, ∗pfx;
Description
These functions generate file names that can safely be used for a tem‐
porary file.
The subroutine always generates a file name using the path-name defined
as in the <stdio.h> header file. If s is NULL, leaves its result in an
internal static area and returns a pointer to that area. The next call
to 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 bytes, where is a
constant defined in <stdio.h>; places its result in that array and
returns s.
The subroutine allows the user to control the choice of a directory.
The argument dir points to the path-name of the directory in which the
file is to be created. If dir is NULL or points to a string which is
not a path-name for an appropriate directory, the path-name defined as
in the <stdio.h> header file is used. If that path-name is not acces‐
sible, will be used as a last resort. This entire sequence can be up-
staged by providing an environment variable TMPDIR in the user's envi‐
ronment, whose value is a path-name for the desired temporary-file
directory.
Many applications prefer their temporary files to have certain favorite
initial letter sequences in their names. Use the pfx argument for
this. This argument may be NULL or point to a string of up to five
characters to be used as the first few characters of the temporary-file
name.
The subroutine uses to get space for the constructed file name, and
returns a pointer to this area. Thus, any pointer value returned from
may serve as an argument to free. For further information, see If can‐
not return the expected result for any reason, that is failed, or none
of the above mentioned attempts to find an appropriate directory was
successful, a NULL pointer will be returned. The and routines generate
a different file name each time they are called.
Files created using these functions and either or 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 use to
remove the file when its use is ended.
Restrictions
If called more than 17,576 times in a single process, these functions
will 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
and the file names are chosen so as to render duplication by other
means unlikely.
See Alsocreat(2), unlink(2), fopen(3s), malloc(3), mktemp(3), tmpfile(3s)tmpnam(3s)