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
178 lines
4.7 KiB
Groff
178 lines
4.7 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.
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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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.\" @(#)funopen.3 8.1 (Berkeley) 6/9/93
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.\" $FreeBSD$
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.\"
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.Dd May 9, 2016
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.Dt FUNOPEN 3
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.Os
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.Sh NAME
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.Nm funopen ,
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.Nm fropen ,
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.Nm fwopen
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.Nd open a stream
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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 funopen "const void *cookie" "int (*readfn)(void *, char *, int)" "int (*writefn)(void *, const char *, int)" "fpos_t (*seekfn)(void *, fpos_t, int)" "int (*closefn)(void *)"
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.Ft FILE *
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.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)"
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.Ft FILE *
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.Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)"
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.Sh DESCRIPTION
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The
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.Fn funopen
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function
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associates a stream with up to four
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.Dq Tn I/O No functions .
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Either
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.Fa readfn
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or
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.Fa writefn
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must be specified;
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the others can be given as an appropriately-typed
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.Dv NULL
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pointer.
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These
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.Tn I/O
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functions will be used to read, write, seek and
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close the new stream.
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.Pp
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In general, omitting a function means that any attempt to perform the
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associated operation on the resulting stream will fail.
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If the close function is omitted, closing the stream will flush
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any buffered output and then succeed.
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.Pp
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The calling conventions of
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.Fa readfn ,
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.Fa writefn ,
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.Fa seekfn
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and
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.Fa closefn
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must match those, respectively, of
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.Xr read 2 ,
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.Xr write 2 ,
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.Xr lseek 2 ,
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and
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.Xr close 2
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with the single exception that they are passed the
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.Fa cookie
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argument specified to
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.Fn funopen
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in place of the traditional file descriptor argument.
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.Pp
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Read and write
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.Tn I/O
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functions are allowed to change the underlying buffer
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on fully buffered or line buffered streams by calling
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.Xr setvbuf 3 .
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They are also not required to completely fill or empty the buffer.
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They are not, however, allowed to change streams from unbuffered to buffered
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or to change the state of the line buffering flag.
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They must also be prepared to have read or write calls occur on buffers other
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than the one most recently specified.
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.Pp
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All user
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.Tn I/O
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functions can report an error by returning \-1.
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Additionally, all of the functions should set the external variable
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.Va errno
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appropriately if an error occurs.
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.Pp
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An error on
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.Fn closefn
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does not keep the stream open.
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.Pp
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As a convenience, the include file
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.In stdio.h
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defines the macros
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.Fn fropen
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and
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.Fn fwopen
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as calls to
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.Fn funopen
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with only a read or write function specified.
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.Sh RETURN VALUES
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Upon successful completion,
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.Fn funopen
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returns a
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.Dv 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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.Fn funopen
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function
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was called without either a read or write function.
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The
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.Fn funopen
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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
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specified for the routine
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.Xr malloc 3 .
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.El
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.Sh SEE ALSO
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.Xr fcntl 2 ,
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.Xr open 2 ,
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.Xr fclose 3 ,
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.Xr fopen 3 ,
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.Xr fopencookie 3 ,
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.Xr fseek 3 ,
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.Xr setbuf 3
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.Sh HISTORY
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The
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.Fn funopen
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functions first appeared in
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.Bx 4.4 .
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.Sh BUGS
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The
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.Fn funopen
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function
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may not be portable to systems other than
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.Bx .
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.Pp
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The
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.Fn funopen
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interface erroneously assumes that
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.Vt fpos_t
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is an integral type; see
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.Xr fseek 3
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for a discussion of this issue.
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