fileno(3p)
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. Otherwise, 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 application to set up the
streams for another application it starts with fork() and 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.
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, 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 .