fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
354 lines
7.6 KiB
Groff
354 lines
7.6 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 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. 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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.\"
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.\" @(#)fopen.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd January 30, 2013
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.Dt FOPEN 3
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.Os
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.Sh NAME
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.Nm fopen ,
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.Nm fdopen ,
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.Nm freopen ,
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.Nm fmemopen
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.Nd stream open functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdio.h
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.Ft FILE *
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.Fn fopen "const char * restrict path" "const char * restrict mode"
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.Ft FILE *
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.Fn fdopen "int fildes" "const char *mode"
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.Ft FILE *
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.Fn freopen "const char *path" "const char *mode" "FILE *stream"
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.Ft FILE *
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.Fn fmemopen "void *restrict *buf" "size_t size" "const char * restrict mode"
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.Sh DESCRIPTION
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The
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.Fn fopen
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function
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opens the file whose name is the string pointed to by
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.Fa path
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and associates a stream with it.
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.Pp
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The argument
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.Fa mode
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points to a string beginning with one of the following letters:
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.Bl -tag -width indent
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.It Dq Li r
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Open for reading.
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The stream is positioned at the beginning of the file.
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Fail if the file does not exist.
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.It Dq Li w
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Open for writing.
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The stream is positioned at the beginning of the file.
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Create the file if it does not exist.
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.It Dq Li a
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Open for writing.
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The stream is positioned at the end of the file.
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Subsequent writes to the file will always end up at the then current
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end of file, irrespective of any intervening
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.Xr fseek 3
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or similar.
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Create the file if it does not exist.
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.El
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.Pp
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An optional
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.Dq Li +
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following
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.Dq Li r ,
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.Dq Li w ,
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or
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.Dq Li a
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opens the file for both reading and writing.
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An optional
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.Dq Li x
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following
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.Dq Li w
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or
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.Dq Li w+
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causes the
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.Fn fopen
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call to fail if the file already exists.
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An optional
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.Dq Li e
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following the above
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causes the
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.Fn fopen
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call to set the
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.Dv FD_CLOEXEC
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flag on the underlying file descriptor.
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.Pp
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The
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.Fa mode
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string can also include the letter
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.Dq Li b
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after either the
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.Dq Li +
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or the first letter.
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This is strictly for compatibility with
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.St -isoC
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and has effect only for
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.Fn fmemopen
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; otherwise
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.Dq Li b
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is ignored.
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.Pp
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Any created files will have mode
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.Do Dv S_IRUSR
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\&|
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.Dv S_IWUSR
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\&|
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.Dv S_IRGRP
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\&|
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.Dv S_IWGRP
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\&|
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.Dv S_IROTH
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\&|
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.Dv S_IWOTH Dc
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.Pq Li 0666 ,
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as modified by the process'
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umask value (see
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.Xr umask 2 ) .
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.Pp
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Reads and writes may be intermixed on read/write streams in any order,
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and do not require an intermediate seek as in previous versions of
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.Em stdio .
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This is not portable to other systems, however;
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.Tn ANSI C
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requires that
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a file positioning function intervene between output and input, unless
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an input operation encounters end-of-file.
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.Pp
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The
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.Fn fdopen
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function associates a stream with the existing file descriptor,
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.Fa fildes .
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The mode
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of the stream must be compatible with the mode of the file descriptor.
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The
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.Dq Li x
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mode option is ignored.
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If the
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.Dq Li e
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mode option is present, the
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.Dv FD_CLOEXEC
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flag is set, otherwise it remains unchanged.
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When the stream is closed via
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.Xr fclose 3 ,
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.Fa fildes
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is closed also.
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.Pp
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The
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.Fn freopen
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function
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opens the file whose name is the string pointed to by
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.Fa path
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and associates the stream pointed to by
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.Fa stream
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with it.
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The original stream (if it exists) is closed.
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The
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.Fa mode
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argument is used just as in the
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.Fn fopen
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function.
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.Pp
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If the
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.Fa path
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argument is
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.Dv NULL ,
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.Fn freopen
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attempts to re-open the file associated with
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.Fa stream
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with a new mode.
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The new mode must be compatible with the mode that the stream was originally
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opened with:
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Streams open for reading can only be re-opened for reading,
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streams open for writing can only be re-opened for writing,
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and streams open for reading and writing can be re-opened in any mode.
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The
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.Dq Li x
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mode option is not meaningful in this context.
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.Pp
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The primary use of the
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.Fn freopen
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function
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is to change the file associated with a
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standard text stream
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.Dv ( stderr , stdin ,
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or
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.Dv stdout ) .
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.Pp
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The
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.Fn fmemopen
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function
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associates the buffer given by the
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.Fa buf
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and
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.Fa size
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arguments with a stream.
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The
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.Fa buf
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argument is either a null pointer or point to a buffer that
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is at least
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.Fa size
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bytes long.
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If a null pointer is specified as the
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.Fa buf
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argument,
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.Fn fmemopen
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allocates
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.Fa size
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bytes of memory. This buffer is automatically freed when the
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stream is closed. Buffers can be opened in text-mode (default) or binary-mode
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(if
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.Dq Li b
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is present in the second or third position of the
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.Fa mode
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argument). Buffers opened in text-mode make sure that writes are terminated with
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a NULL byte, if the last write hasn't filled up the whole buffer. Buffers
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opened in binary-mode never append a NULL byte.
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.Sh RETURN VALUES
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Upon successful completion
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.Fn fopen ,
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.Fn fdopen
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and
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.Fn freopen
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return a
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.Tn FILE
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pointer.
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Otherwise,
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.Dv NULL
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is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa mode
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argument
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to
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.Fn fopen ,
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.Fn fdopen ,
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.Fn freopen ,
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or
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.Fn fmemopen
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was invalid.
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.El
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.Pp
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The
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.Fn fopen ,
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.Fn fdopen ,
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.Fn freopen
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and
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.Fn fmemopen
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functions
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may also fail and set
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.Va errno
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for any of the errors specified for the routine
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.Xr malloc 3 .
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.Pp
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The
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.Fn fopen
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function
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may also fail and set
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.Va errno
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for any of the errors specified for the routine
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.Xr open 2 .
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.Pp
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The
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.Fn fdopen
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function
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may also fail and set
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.Va errno
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for any of the errors specified for the routine
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.Xr fcntl 2 .
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.Pp
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The
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.Fn freopen
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function
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may also fail and set
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.Va errno
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for any of the errors specified for the routines
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.Xr open 2 ,
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.Xr fclose 3
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and
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.Xr fflush 3 .
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.Pp
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The
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.Fn fmemopen
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function
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may also fail and set
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.Va errno
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if the
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.Fa size
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argument is 0.
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.Sh SEE ALSO
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.Xr open 2 ,
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.Xr fclose 3 ,
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.Xr fileno 3 ,
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.Xr fseek 3 ,
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.Xr funopen 3
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.Sh STANDARDS
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The
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.Fn fopen
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and
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.Fn freopen
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functions
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conform to
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.St -isoC ,
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with the exception of the
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.Dq Li x
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mode option which conforms to
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.St -isoC-2011 .
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The
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.Fn fdopen
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function
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conforms to
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.St -p1003.1-88 .
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The
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.Dq Li e
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mode option does not conform to any standard
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but is also supported by glibc.
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The
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.Fn fmemopen
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function
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conforms to
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.St -p1003.1-2008 .
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The
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.Dq Li b
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mode does not conform to any standard
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but is also supported by glibc.
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