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.Dd May 31, 2020
.Dt ZCK_DELTA_SIZE 1
.Os
.Sh NAME
.Nm zck_delta_size
.Nd calculate the differences between two zchunk files
.Sh SYNOPSIS
.Nm
.Op Fl v | Fl -verbose
.Ar file1
.Ar file2
.Nm
.Fl ? | Fl -help | Fl -usage | Fl -version
.Sh DESCRIPTION
The
.Nm
utility examines two zchunk compressed files and determines how similar
they are: how many chunks are the same between the files, so that tools
like e.g.
.Xr rsync 1
or
.Xr zckdl 1
could only transfer the small parts that differ instead of the full files.
This is especially useful for structured files that have been compressed
using the
.Xr zck 1
tool's
.Fl s Po Fl -split Pc
option.
.Pp
The
.Nm
utility accepts the following optional arguments:
.Pp
.Bl -tag -width indent
.It Fl v , Fl -verbose
Verbose operation; display some diagnostic output.
.It Fl ? , Fl -help
Display program usage information and exit.
.It Fl -usage
Display brief program usage information and exit.
.It Fl -version
Display program version information and exit.
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Examine two zchunk files:
.Pp
.Dl zck_delta_size doc1.txt.zck doc2.txt.zck
.Pp
.Sh SEE ALSO
.Xr unzck 1 ,
.Xr zck 1 ,
.Xr zck_gen_zdict 1 ,
.Xr zck_read_header 1 ,
.Xr zckdl 1
.Sh AUTHOR
The
.Nm
utility was written by
.An Jonathan Dieter Aq jdieter@gmail.com .
This manual page stub was written by
.An Peter Pentchev Aq roam@ringlet.net .