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FILENO(3P) POSIX Programmer's Manual FILENO(3P)
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.
fileno — map a stream pointer to a file descriptor
#include <stdio.h>
int fileno(FILE *stream);
The fileno() function shall return the integer file descriptor
associated with the stream pointed to by stream.
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.
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.
None.
None.
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).
None.
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)
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)
Pages that refer to this page: stdio.h(0p), dirfd(3p), stdin(3p)