mirror of https://github.com/mkerrisk/man-pages
118 lines
3.6 KiB
Groff
118 lines
3.6 KiB
Groff
.\" Copyright (c) 1990, 1991 The Regents of the University of California.
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.\" and Copyright (C) 2021 Michael Kerrisk <mtk.manpages@gmail.com>
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\" %%%LICENSE_END
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.\"
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.\" Converted for Linux, Mon Nov 29 14:24:40 1993, faith@cs.unc.edu
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.\" Added remark on EBADF for fileno, aeb, 2001-03-22
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.\"
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.TH FILENO 3 2021-03-22 "" "Linux Programmer's Manual"
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.SH NAME
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fileno \- obtain file descriptor of a stdio stream
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.SH SYNOPSIS
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.nf
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.B #include <stdio.h>
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.PP
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.BI "int fileno(FILE *" stream );
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.fi
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.PP
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.RS -4
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.RE
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.PP
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.BR fileno ():
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.nf
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_POSIX_C_SOURCE
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.fi
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.SH DESCRIPTION
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.PP
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The function
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.BR fileno ()
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examines the argument
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.I stream
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and returns the integer file descriptor used to implement this stream.
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The file descriptor is still owned by
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.I stream
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and will be closed when
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.BR fclose (3)
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is called.
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Duplicate the file descriptor with
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.BR dup (2)
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before passing it to code that might close it.
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.PP
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For the nonlocking counterpart, see
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.BR unlocked_stdio (3).
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.SH RETURN VALUE
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On success,
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.BR fileno ()
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returns the file descriptor associated with
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.IR stream .
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On failure, \-1 is returned and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EBADF
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.I stream
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is not associated with a file.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.ad l
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.nh
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.TS
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allbox;
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lbx lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR fileno ()
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T} Thread safety MT-Safe
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.TE
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.hy
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.ad
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.sp 1
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.SH CONFORMING TO
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The function
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.BR fileno ()
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conforms to POSIX.1-2001 and POSIX.1-2008.
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.SH SEE ALSO
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.BR open (2),
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.BR fdopen (3),
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.BR stdio (3),
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.BR unlocked_stdio (3)
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