.CD "cdiff \(en context diff"
.SX "cdiff\fR [\fB\(enc\fIn\fR] \fIoldfile \fInewfile"
.FL "\(enc" "Provide \fIn\fR lines of context"
.EX "cdiff old new >f" "Write context diff on \fIf\fR"
.EX "cdiff \(enc1 old new >f" "Use only 1 line of context"
.PP
\fICdiff\fR produces a context diff by first running \fIdiff\fR and then 
adding context.  
Some update programs, like \fIpatch\fR, can use context diffs to update
files, even in the presence of other, independent changes.