\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename wdiff.info
@settitle A word difference finder
@finalout
@setchapternewpage odd
@c %**end of header

@ifinfo
This file documents the @code{wdiff} command, which compares two
files, finding which words have been deleted or added to the first
for getting the second.

Copyright (C) 1992 by the Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end ifinfo

@titlepage
@title wdiff
@subtitle The word difference finder
@subtitle Edition 0.04, for wdiff Version 0.04
@subtitle November 1992
@author by Francois Pinard

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1992 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end titlepage

@node Top, Copying, (dir), (dir)

@ifinfo
This file documents the @code{wdiff} command, as of release 0.04.  This
command compares two files, finding which words have been deleted or
added to the first for getting the second.
@end ifinfo

@menu
* Copying::			How you can copy and share @code{wdiff}.
* Overview::                    Preliminary information.
* Invoking wdiff::              How to run @code{wdiff}.
* Examples::                    Actual examples of @code{wdiff} usage.

 --- The Detailed Node Listing ---
@end menu

@node Copying, Overview, Top, Top
@include gpl.texinfo

@node Overview, Invoking wdiff, Copying, Top
@chapter Overview

The program @code{wdiff} is a front end to @code{diff} for comparing
files on a word per word basis.  A word is anything between whitespace.
This is useful for comparing two texts in which a few words have been
changed and for which paragraphs have been refilled.  It works by
creating two temporary files, one word per line, and then executes
@code{diff} on these files.  It collects the @code{diff} output and uses
it to produce a nicer display of word differences between the original
files.

Ideally, @code{wdiff} should avoid calling @code{diff} and do all the
work internally, allowing it to be faster and more polished.  However, I
loathe replicating the @code{diff} algorithm and development effort,
instead of improving @code{diff} itself.  It would be more sensible to
integrate @code{wdiff} into @code{diff} than the other way around.  I
did it this way only because I had a sudden and urgent need for it, and
it would have taken too much time to integrate it correctly into GNU
@code{diff}.  Your advice or opinions about this are welcome.

@code{wdiff} was written by Francois Pinard.
@c *** Comment placer la ce'dille?
Please report bugs to @w{@file{bug-gnu-utils@@prep.ai.mit.edu}}.
Include the version number, which you can find by running @w{@samp{wdiff
--version}}.  Include in your message sufficient input to reproduce the
problem and also, the output you expected.

@node Invoking wdiff, Examples, Overview, Top
@chapter Invoking @code{wdiff}

The format for running the @code{wdiff} program is:

@example
wdiff @var{option} @dots{} @var{old_file} @var{new_file}
@end example

@code{wdiff} compares files @var{old_file} and @var{new_file} and
produces an annotated copy of @var{new_file} on standard output.
@code{wdiff} will exit with a status of 0 if no differences were found,
a status of 1 if any differences were found, or a status of 2 for any
error.

In this documentation, @dfn{deleted text} refers to text in
@var{old_file} which is not in @var{new_file}, while @dfn{inserted text}
refers to text on @var{new_file} which is not in @var{old_file}.

@code{wdiff} supports the following command line options:

@table @samp
@item --help
@itemx -h
Print an informative help message describing the options.

@item --version
@itemx -v
Print the version number of @code{wdiff} on the standard error output.

@item --no-deleted
@itemx -1
Avoid producing deleted words on the output.  If neither @samp{-1} or
@samp{-2} is selected, the original right margin may be exceeded for
some lines.

@item --no-inserted
@itemx -2
Avoid producing inserted words on the output.  When this flag is given,
the whitespace in the output is taken from @var{old_file} instead of
@var{new_file}.  If neither @samp{-1} or @samp{-2} is selected, the
original right margin may be exceeded for some lines.

@item --no-common
@itemx -3
Avoid producing common words on the output.  When this option is not
selected, common words and whitespace are taken from @var{new_file},
unless option @samp{-2} is given, in which case common words and
whitespace are rather taken from @var{old_file}.  When selected,
differences are separated from one another by lines of dashes.
Moreover, if this option is selected at the same time as @samp{-1} or
@samp{-2}, then none of the output will have any emphasis, i.e. no bold
or underlining.  Finally, if this option is not selected, but both
@samp{-1} and @samp{-2} are, then sections of common words between
differences are segregated by lines of dashes.

@item --statistics
@itemx -s
On completion, for each file, the total number of words, the number of
common words between the files, the number of words deleted or inserted
and the number of words that have changed is output.  (A changed word is
one that has been replaced or is part of a replacement.)  Except for the
total number of words, all of the numbers are followed by a percentage
relative to the total number of words in the file.

@item --auto-pager
@itemx -a
Some initiatives which were previously automatically taken in previous
versions of @code{wdiff} are now put under the control of this option.
By using it, a pager is interposed whenever the @code{wdiff} output is
directed to the user's terminal.  Without this option, no pager will be
called, the user is then responsible for explicitly piping @code{wdiff}
output into a pager, if required.

The pager is selected by the value of the @code{PAGER} environment
variable when @code{wdiff} is run.  If @code{PAGER} is not defined at
run time, then a default pager, selected at installation time, will be
used instead.  A defined but empty value of @code{PAGER} means no pager
at all.

When a pager is interposed through the use of this option,
one of the options @samp{-l} or @samp{-t} is also selected, depending on
whether the string @samp{less} appears in the pager's name or not.

It is often useful to define @samp{wdiff} as an alias for @samp{wdiff
-a}.  However, this @emph{hides} the normal @code{wdiff} behaviour.  The
default behaviour may be restored simply by piping the output from
@code{wdiff} through @code{cat}.  This dissociates the output from the
user's terminal.

@item --printer
@itemx -p
Use over-striking to emphasize parts of the output.  Each character of the
deleted text is underlined by writing an underscore @samp{_} first,
then a backspace and then the letter to be underlined.  Each character of the
inserted text is emboldened by writing it twice, with a backspace in
between.  This option is not selected by default.

@item --less-mode
@itemx -l
Use over-striking to emphasize parts of output.  This option works as
option @code{-p}, but also over-strikes whitespace associated with
inserted text.  @code{less} shows such whitespace using reverse video.
This option is not selected by default.  However, it is automatically
turned on whenever @code{wdiff} launches the pager @code{less}.  See
option @samp{-a}.

This option is commonly used in conjunction with @code{less}:

@example
wdiff -l @var{old_file} @var{new_file} | less
@end example

@item --terminal
@itemx -t
Force the production of @code{termcap} strings for emphasising parts of
output, even if the standard output is not associated with a terminal.
The @samp{TERM} environment variable must contain the name of a valid
@code{termcap} entry.  If the terminal description permits, underlining
is used for marking deleted text, while bold or reverse video is used
for marking inserted text.  This option is not selected by default.
However, it is automatically turned on whenever @code{wdiff} launches a
pager, and it is known that the pager is @emph{not} @code{less}.  See
option @samp{-a}.

This option is commonly used when @code{wdiff} output is not redirected,
but sent directly to the user terminal, as in:

@example
wdiff -t @var{old_file} @var{new_file}
@end example

A common kludge uses @code{wdiff} together with the pager @code{more},
as in:

@example
wdiff -t @var{old_file} @var{new_file} | more
@end example

However, some versions of @code{more} use @code{termcap} emphasis for
their own purposes, so strange interactions are possible.

@item --start-delete @var{argument}
@itemx -w @var{argument}
Use @var{argument} as the @dfn{start delete} string.  This string will
be output prior to any sequence of deleted text, to mark where it
starts.  By default, no start delete string is used unless there is no
other means of distinguishing where such text starts; in this case the
default start delete string is @samp{[-}.

@item --end-delete @var{argument}
@itemx -x @var{argument}
Use @var{argument} as the @dfn{end delete} string.  This string will be
output after any sequence of deleted text, to mark where it ends.  By
default, no end delete string is used unless there is no other means of
distinguishing where such text ends; in this case the default end delete
string is @samp{-]}.

@item --start-insert @var{argument}
@itemx -y @var{argument}
Use @var{argument} as the @dfn{start insert} string.  This string will
be output prior to any sequence of inserted text, to mark where it
starts.  By default, no start insert string is used unless there is no
other means of distinguishing where such text starts; in this case the
default start insert string is @samp{@{+}.

@item --end-insert @var{argument}
@itemx -z @var{argument}
Use @var{argument} as the @dfn{end insert} string.  This string will be
output after any sequence of inserted text, to mark where it ends.  By
default, no end insert string is used unless there is no other means of
distinguishing where such text ends; in this case the default end insert
string is @samp{+@}}.

@item --avoid-wraps
@itemx -n
Avoid spanning the end of line while showing deleted or inserted text.
Any single fragment of deleted or inserted text spanning many lines will
be considered as being made up of many smaller fragments not containing
a newline.  So deleted text, for example, will have an end delete string
at the end of each line, just before the new line, and a start delete
string at the beginning of the next line.  A long paragraph of inserted
text will have each line bracketed between start insert and end insert
strings.  This behaviour is not selected by default.
@end table

Note that options @samp{-p}, @samp{-t}, and @samp{-[wxyz]} are not
mutually exclusive.  If you use a combination of them, you will merely
accumulate the effect of each.  Option @samp{-l} is a variant of option
@samp{-p}.

@node Examples,  , Invoking wdiff, Top
@chapter Actual examples of @code{wdiff} usage

This section presents a few examples of usage, most of them have been
contributed by @code{wdiff} users.

@itemize @bullet
@item Change bars example.

This example comes from a discussion with Joe Wells,
@samp{jbw@@cs.bu.edu}.

The following command produces a copy of @var{new_file}, shifted right
one space to accommodate change bars since the last revision, ignoring
those changes coming only from paragraph refilling.  Any line with new
or changed text will get a @samp{|} in column 1.  However, deleted text
is not shown nor marked.

@example
wdiff -1n @var{old_file} @var{new_file} |
  sed -e 's/^/  /;/@{+/s/^ /|/;s/@{+//g;s/+@}//g'
@end example

Here is how it works.  Word differences are found, paying attention only
to additions, as requested by option @samp{-1}.  For bigger changes
which span line boundaries, the insert bracket strings are repeated on
each output line, as requested by option @samp{-n}.  This output is then
reformatted with a @code{sed} script which shifts the text right two
columns, turns the initial space into a bar only if there is some new
text on that line, then removes all insert bracket strings.

@item @code{La@TeX{}} example.

This example has been provided by Steve Fisk,
@samp{fisk@@polar.bowdoin.edu}.

The following uses La@TeX{} to put deleted text in boxes, and new text
in double boxes:

@example
wdiff -w "\fbox@{" -x "@}" -y "\fbox@{\fbox@{" -z "@}@}" @dots{}
@end example

@noindent
works nicely.

@item @code{troff} example.

This example comes from Paul Fox, @samp{pgf@@cayman.com}.

Using @code{wdiff}, with some @code{troff}-specific delimiters gives
@emph{much} better output.  The delimiters I used:

@example
wdiff -w'\s-5' -x'\s0' -y'\fB' -z'\fP' @dots{}
@end example

This makes the pointsize of deletions 5 points smaller than normal, and
emboldens insertions.  Fantastic!

I experimented with:

@example
wdiff -w'\fI' -x'\fP' -y'\fB' -z'\fP'
@end example

since that's more like the defaults you use for terminals/printers, but
since I actually use italics for emphasis in my documents, I thought the
point size thing was clearer.

I tried it on code, and it works surprisingly well there, too...

@end itemize

@bye
