NAME

tmpnam, tempnam − create a name for a temporary file

SYNOPSIS

#include <stdio.h>

char ∗tmpnam(s)
char ∗s;

char ∗tempnam(dir, pfx)
char ∗dir;
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 P_tmpdir 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 should be an address of an array of at least L_tmpnam bytes, where L_tmpnam is a constant defined in <stdio.h>; tmpnam places its result in that array and returns s.

tempnam allows the user to specify 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, an environment variable TMPDIR is used instead of dir. If TMPDIR is not defined or the specified directory cannot be accessed, the path-prefix defined as P_tmpdir in the <stdio.h> header file is used.  If that directory is not accessible, /tmp will be used as a last resort. 

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 to be used as the first few characters of the temporary-file name. 

tempnam uses malloc(3) 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.  If tempnam cannot return the expected result for any reason, i.e.  malloc failed or none of the above mentioned attempts to find an appropriate directory was successful, a NULL pointer is returned. 

FILES

/var/tmp

SEE ALSO

creat(2), unlink(2), fopen(3S), malloc(3), mktemp(3),

NOTES

These functions generate a different file name each time they are called.  Files created using these functions and either fopen(3S) 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,

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(3). 

BUGS

TMP_MAX is 26, this may be too little. 

NEWS-OSRelease 4.1C