C in a Nutshell

Name

tmpnam

Synopsis

Generates a unique filename

#include <stdio.h>
char *tmpnam( char *s );

The tmpnam() function generates a unique filename suitable for using for temporary files, and returns a pointer to the name string. If the pointer argument s is not a null pointer, then tmpnam() places the name string in a buffer addressed by s. The size of the buffer is assumed to be at least equal to the macro L_tmpnam. If s is a null pointer, then the return value points to the filename in tmpnam()’s internal, static buffer, where it may be modified by subsequent tmpnam() calls.

If you use a name supplied by tmpnam() to create a file, that does not mean the file is a temporary file in the sense of tmpfile(); it will not be automatically deleted on closing.

The tmpnam() function generates a different name each time it is called, and can generate at least TMP_MAX distinct names (some of which may be used by tmpfile()). The macros L_tmpnam and TMP_MAX are defined in stdio.h. TMP_MAX is greater than or equal to 25. The tmpnam() function returns a null pointer on failure.

Example

char buffer[L_tmpnam], *name = buffer;
FILE *fpOut;
int result;

name =tmpnam( buffer );

if ( name == NULL )
{
  fputs( "Failed to generate temporary file name", stderr );
  return -1;
}

fpOut = fopen( name, "w+" );
/* ... write something in the file, edit it ... */
fclose( fpOut );
printf( "Results saved in %s\n", name );

See Also

tmpfile(), rename()