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