.\"-
.\" Copyright 2003-2005 Colin Percival
.\" All rights reserved
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted providing 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 ``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 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,
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.\"
.Dd December 22, 2022
.Dt BSPATCH 1
.Os
.Sh NAME
.Nm bspatch
.Nd apply a patch built with
.Xr bsdiff 1
.Sh SYNOPSIS
.Nm
.Ar oldfile newfile patchfile
.Sh DESCRIPTION
The
.Nm
utility
generates
.Ar newfile
from
.Ar oldfile
and
.Ar patchfile
where
.Ar patchfile
is a binary patch built by
.Xr bsdiff 1 .
.Pp
The
.Nm
utility
uses memory equal to the size of
.Ar oldfile
plus the size of
.Ar newfile ,
but can tolerate a very small working set without a dramatic loss
of performance.
.Sh SEE ALSO
.Xr bsdiff 1
.Sh AUTHORS
.An Colin Percival Aq Mt cperciva@FreeBSD.org
.Sh BUGS
The
.Nm
utility does not verify that
.Ar oldfile
is the correct source file for
.Ar patchfile .
Attempting to apply a patch to the wrong file will usually produce
garbage; consequently it is strongly recommended that users of
.Nm
verify that
.Ar oldfile
matches the source file from which
.Ar patchfile
was built, by comparing cryptographic hashes, for example.
Users may also wish to verify after running
.Nm
that
.Ar newfile
matches the target file from which
.Ar patchfile
was built.