.Dd January 15, 2017
.Dt GZERROR 3
.Os
.
.Sh NAME
.Nm gzerror ,
.Nm gzclearerr
.Nd check and reset compressed file error
.
.Sh LIBRARY
.Lb libz
.
.Sh SYNOPSIS
.In zlib.h
.Ft const char *
.Fn gzerror "gzFile file" "int *errnum"
.Ft void
.Fn gzclearerr "gzFile file"
.
.Sh DESCRIPTION
.Fn gzerror
returns the error message for the last error
which occured on the given compressed file.
.Fa errnum
is set to the zlib error number.
If an error occurred in the file system
and not in the compression library,
.Fa errnum
is set to
.Dv Z_ERRNO
and the application may consult
.Va errno
to get the exact error code.
.
.Pp
The application must not modify the returned string.
Future calls to this function
may invalidate the previously returned string.
If
.Fa file
is closed,
then the string previously returned by
.Fn gzerror
will no longer be available.
.
.Pp
.Fn gzerror
should be used to distinguish errors from end-of-file
for those functions that do not distinguish those cases
in their return values.
.
.Pp
.Fn gzclearerr
clears the error and end-of-file for
.Fa file .
This is analogous to the
.Xr clearerr 3
function in stdio.
This is useful for continuing to read a gzip file
that is being written concurrently.
.
.Sh SEE ALSO
.Xr gzeof 3 ,
.Xr gzread 3 ,
.Xr gzwrite 3
.
.Sh HISTORY
This manual page was converted from
.In zlib.h
to mdoc format by
.An C. McEnroe Aq Mt june@causal.agency .
.
.Sh AUTHORS
.An Jean-loup Gailly Aq Mt jloup@gzip.org
.An Mark Adler Aq Mt madler@alumni.caltech.edu