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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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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 shall fail if:
EBADF The stream is not associated with a file.
The fileno() function may fail if:
EBADF The file descriptor underlying stream is not a valid file
descriptor.
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.1‐2017, stdio.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 FILENO(3P)
Pages that refer to this page: stdio.h(0p), dirfd(3p), stdin(3p)
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