|| POSIX Programmer's Manual
PROLOG This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult 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
int fileno(FILE *
fileno() function shall return the integer file descriptor associated with the stream pointed to by
RETURN VALUE Upon successful completion,
fileno() shall return the integer value of the file descriptor associated with
stream. Otherwise, the value -1 shall be returned and
errno set to indicate the error.
() function may fail if:
stream argument is not a valid stream.
The following sections are informative.
APPLICATION USAGE None.
RATIONALE Without some specification of which file descriptors are associated with these streams, it is impossible for an application to set up the streams for another application it starts with
exec. In particular, it would not be possible to write a portable version of the
sh command interpreter (although there may be other constraints that would prevent that portability).
FUTURE DIRECTIONS None.
Interaction of File Descriptors and Standard I/O Streams,
stdin(), the Base Definitions volume of IEEE Std 1003.1-2001,
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, Copyright (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.opengroup.org/unix/online.html .