NAME

fileno(), fileno_unlocked() − map stream pointer to file descriptor

SYNOPSIS

#include <stdio.h>

int fileno(FILE *stream);

int fileno_unlocked(FILE *stream);

DESCRIPTION

fileno() returns the integer file descriptor associated with the named stream; see open(2).

The following symbolic values in <unistd.h> define the file descriptors associated with stdin, stdout, and stderr when a program is started :

STDIN_FILENO Value of zero for standard input, stdin. 

STDOUT_FILENO Value of 1 for standard output, stdout. 

STDERR_FILENO Value of 2 for standard error, stderr. 

fileno_unlocked is identical to fileno except it does not perform any internal locking of the stream for multi-thread applications.  fileno_unlocked can be used by multi-thread applications which have already used flockfile() to acquire a mutual exclusion lock for the stream (see flockfile(3S)).

RETURN VALUE

Upon error, fileno() and fileno_unlocked() return −1. 

SEE ALSO

open(2), flockfile(3S), fopen(3S). 

STANDARDS CONFORMANCE

fileno(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996