FILENO(3P)                                          POSIX Programmer's Manual                                         FILENO(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       fileno - map a stream pointer to a file descriptor

SYNOPSIS
       #include <stdio.h>

       int fileno(FILE *stream);


DESCRIPTION
       The fileno() function shall return the integer file descriptor associated with the stream pointed to by stream.

RETURN VALUE
       Upon  successful completion, fileno() shall return the integer value of the file descriptor associated with stream.  Oth-
       erwise, the value -1 shall be returned and errno set to indicate the error.

ERRORS
       The fileno() function may fail if:

       EBADF  The stream argument is not a valid stream.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       Without some specification of which file descriptors are associated with these streams, it is impossible for an  applica-
       tion  to set up the streams for another application it starts with fork() and exec. In particular, it would not be possi-
       ble to write a portable version of the sh command interpreter (although there may be other constraints that would prevent
       that portability).

FUTURE DIRECTIONS
       None.

SEE ALSO
       Interaction  of  File  Descriptors  and  Standard I/O Streams, fdopen(), fopen(), stdin(), the Base Definitions volume of
       IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    FILENO(3P)