tmpnam

tmpnam

Generate Temporary Filename

Portability: ISO/ANSI C conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
CAUTION
IMPLEMENTATION
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <stdio.h>

char *tmpnam(char *buf);

DESCRIPTION

tmpnam generates a string that is a valid filename and is not the same as the name of any existing file. If a file with this name is opened, it continues to exist after program termination. tmpnam generates up to TMP_MAX filenames, a different name each time it is called.

For a program compiled with the posix option, the name returned by tmpnam defines a file in the HFS directory /tmp .

RETURN VALUE

If buf is NULL , tmpnam leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to tmpnam may modify that same object.

If buf is not NULL , it is assumed to point to an array of at least L_tmpnam characters; tmpnam writes its result in that array and returns the argument as its value.

CAUTION

The generated filenames are designed to be unique. The library makes 100 attempts to generate a unique filename at each call to tmpnam . If after 100 attempts it cannot generate a unique filename, tmpnam returns NULL .

IMPLEMENTATION

This implementation essentially assigns a value of infinity to TMP_MAX because it is virtually impossible to cause an error by calling tmpnam too many times.

The returned filename strings are composed as follows:

OS/390

dsn:userid.jobid. $ddmonyr.$hhmmss. $tens-of-microseconds

Here is an example:

dsn:GEORGE.JOB01234.$10NOV88.$142253.$0000792

If a userid is not available, use "C-TMP" . Here is an example:

dsn:C-TMP.JOB01234.$10NOV88.$142253.$0000792

CMS

cms:$ddmonyr  $tens-of-microseconds fml

Here is an example:

cms:$10NOV88 $0000792 A1

The CMS filemode letter is chosen from the read and write disk with the most space.

USS

/tmp/logonid.pid.ddmonyr.hhmmss.tens-of-microseconds

For example:

/tmp/JANE.524290.10NOV94.142253.0000792

EXAMPLE

#include <stdio.h>
#include <stdlib.h>

main()
{
   char *name;
   FILE *temp;
   name = tmpnam(NULL);
   if (name == NULL) exit(EXIT_FAILURE);
   temp = fopen(name, "w");
   fputs("Hello, temporary world.\n", temp);
   fclose(temp);
   remove(name);
}

RELATED FUNCTIONS

tmpfile