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.\" Copyright (c) 2014 Xin LI <delphij@FreeBSD.org>
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd December 6, 2018
.Dt ZOPEN 3
.Os
.Sh NAME
.Nm zopen
.Nd open a gzip compressed stream
.Sh LIBRARY
.Lb libz
.Sh SYNOPSIS
.Ft FILE *
.Fn zopen "const char *path" "const char *mode"
.Ft FILE *
.Fn zdopen "int fd" "const char *mode"
.Sh DESCRIPTION
The
.Fn zopen
function opens a gzip file whose name is the string pointed to by
.Fa path
and returns a stream which can be used to access the uncompressed contents
of the file.
The
.Fn zdopen
variant takes a gzip file referenced by the file descriptor
.Fa fd ,
analogous to
.Xr fdopen 3 .
They are wrappers around
.Xr zlib 3
and the standard stream I/O APIs.
.Pp
The argument
.Fa mode
has the same meaning as it does in
.Xr fopen 3 .
.Pp
The
.Fn zopen
and
.Fn zdopen
functions will associate the read, write, seek and close
functions of
.Xr zlib 3
with the returned stream.
.Sh RETURN VALUES
Upon successful completion
.Fn zopen
and
.Fn zdopen
return a
.Tn FILE
pointer.
Otherwise,
.Dv NULL
is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
In addition to the errors documented for
.Xr fopen 3
and
.Xr fdopen 3 ,
the functions may also fail for:
.Bl -tag -width Er
.It Bq Er ENOMEM
Insufficient memory is available.
.El
.Sh COMPATIBILITY
The implementation of
.Fn zopen
function first appeared in
.Nx 1.6
and
.Fx 4.5 .
.Fn zdopen
first appeared in
.Fx 13.0 .
These functions may not be portable to systems other than
.Fx .
.Sh SEE ALSO
.Xr fdopen 3 ,
.Xr fopen 3 ,
.Xr funopen 3 ,
.Xr zlib 3
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