.\" Copyright (c) 2014 Xin LI <delphij@FreeBSD.org>
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.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