tmpnam(3S) DG/UX R4.11MU05 tmpnam(3S)
NAME
tmpnam, tempnam - create a name for a temporary file
SYNOPSIS
#include <stdio.h>
char *tmpnam(char *s);
char *tempnam(const char *dir, const char *pfx);
DESCRIPTION
These functions generate file names that can safely be used for a
temporary file.
tmpnam always generates a file name using the path-prefix defined as
Ptmpdir in the stdio.h header file. 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
Ltmpnam bytes, where Ltmpnam is a constant defined in stdio.h;
tmpnam places its result in that array and returns s.
tempnam 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
Ptmpdir in the stdio.h header file is used. If that directory is
not accessible, tmp will be used as a last resort. This entire
sequence can be up-staged by providing an environment variable TMPDIR
in the user's environment, whose value is the name of 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.
tempnam uses malloc to get space for the constructed file name, and
returns a pointer to this area. Thus, any pointer value returned
from tempnam may serve as an argument to free [see malloc(3C)]. If
tempnam cannot return the expected result for any reason-- for
example, malloc failed--or none of the above mentioned attempts to
find an appropriate directory was successful, a NULL pointer will be
returned.
tempnam fails if there is not enough space.
Files
ptmpdir
/var/tmp
Considerations for Threads Programming
+---------+-----------------------------+
| | async- |
|function | reentrant cancel cancel |
| | point safe |
+---------+-----------------------------+
|tempnam | Y N N |
|tmpnam | Y N N |
+---------+-----------------------------+
REFERENCES
creat(2), unlink(2), reentrant(3), malloc(3C), mktemp(3C), fopen(3S),
tmpfile(3S)
NOTICES
These functions generate a different file name each time they are
called.
Files created using these functions and either fopen or creat 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 TMPMAX (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 and the file names are chosen to render duplication by
other means unlikely.
When used in a multi-threaded application, tmpnam should have a non-
NULL argument.
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