PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       fileno — map a stream pointer to a file descriptor

SYNOPSIS         top

       #include <stdio.h>

       int fileno(FILE *stream);

DESCRIPTION         top

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

RETURN VALUE         top

       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         top

       The fileno() function may fail if:

       EBADF  The stream argument is not a valid stream, or the stream is
              not associated with a file.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       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         top

       None.

SEE ALSO         top

       Section 2.5.1, Interaction of File Descriptors and Standard I/O
       Streams, dirfd(3p), fdopen(3p), fopen(3p), stdin(3p)

       The Base Definitions volume of POSIX.1‐2008, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                          FILENO(3P)