fileno - Determine File Handle

Syntax

#include <stdio.h>
int fileno(FILE *stream);

fileno determines the file handle currently associated with stream.

Note: In earlier releases of C Set ++, fileno began with an underscore (_fileno). Because it is defined by the X/Open standard, the underscore has been removed. For compatibility, The Developer's Toolkit will map _fileno to fileno for you.

fileno returns the file handle. If the function fails, the return value is -1 and the errno variable may be set to one of the following values: compact break=fit.

Value

Meaning

The input stream is NULL.

The input stream file is not a stream file.

The result is undefined if stream does not specify an open file.

This example determines the file handle of the stderr data stream.

#include <stdio.h>
int main(void)
{
   int result;

   result = 0xFFFF & fileno(stderr);
   printf("The file handle associated with stderr is %d.\n", result);
   return 0;

   /****************************************************************************
      The output should be:

      The file handle associated with stderr is 2.
   ****************************************************************************/
}

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