Copyright (C) 1992, 1994 Free Software Foundation, Inc.
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The program wdiff
is a front end to 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
diff
on these files. It collects the diff
output and uses
it to produce a nicer display of word differences between the original
files.
Ideally, wdiff
should avoid calling diff
and do all the
work internally, allowing it to be faster and more polished. However, I
loathe replicating the diff
algorithm and development effort,
instead of improving diff
itself. It would be more sensible to
integrate wdiff
into 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
diff
. Your advice or opinions about this are welcome.
wdiff
was written by Pinard. Please report
bugs to `bug-gnu-utils@prep.ai.mit.edu'. Include the version
number, which you can find by running `wdiff --version'.
Include in your message sufficient input to reproduce the problem
and also, the output you expected.
wdiff
The format for running the wdiff
program is:
wdiff option ... old_file new_file
wdiff
compares files old_file and new_file and
produces an annotated copy of new_file on standard output. The
empty string or the string `-' denotes standard input, but standard
input cannot be used twice in the same invocation. The complete path of
a file should be given, a directory name is not accepted. 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, deleted text refers to text in old_file which is not in new_file, while inserted text refers to text on new_file which is not in old_file.
wdiff
supports the following command line options:
wdiff
on the standard error output.
wdiff
are now put under the control of this option.
By using it, a pager is interposed whenever the 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 wdiff
output into a pager, if required.
The pager is selected by the value of the PAGER
environment
variable when wdiff
is run. If 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 PAGER
means no pager
at all.
When a pager is interposed through the use of this option,
one of the options `-l' or `-t' is also selected, depending on
whether the string `less' appears in the pager's name or not.
It is often useful to define `wdiff' as an alias for `wdiff
-a'. However, this hides the normal wdiff
behaviour. The
default behaviour may be restored simply by piping the output from
wdiff
through cat
. This dissociates the output from the
user's terminal.
-p
, but also over-strikes whitespace associated with
inserted text. less
shows such whitespace using reverse video.
This option is not selected by default. However, it is automatically
turned on whenever wdiff
launches the pager less
. See
option `-a'.
This option is commonly used in conjunction with less
:
wdiff -l old_file new_file | less
termcap
strings for emphasising parts of
output, even if the standard output is not associated with a terminal.
The `TERM' environment variable must contain the name of a valid
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 wdiff
launches a
pager, and it is known that the pager is not less
. See
option `-a'.
This option is commonly used when wdiff
output is not redirected,
but sent directly to the user terminal, as in:
wdiff -t old_file new_fileA common kludge uses
wdiff
together with the pager more
,
as in:
wdiff -t old_file new_file | moreHowever, some versions of
more
use termcap
emphasis for
their own purposes, so strange interactions are possible.
Note that options `-p', `-t', and `-[wxyz]' are not mutually exclusive. If you use a combination of them, you will merely accumulate the effect of each. Option `-l' is a variant of option `-p'.
wdiff
usage
This section presents a few examples of usage, most of them have been
contributed by wdiff
users.
wdiff -1n old_file new_file | sed -e 's/^/ /;/{+/s/^ /|/;s/{+//g;s/+}//g'Here is how it works. Word differences are found, paying attention only to additions, as requested by option `-1'. For bigger changes which span line boundaries, the insert bracket strings are repeated on each output line, as requested by option `-n'. This output is then reformatted with a
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.
LaTeX
example.
This example has been provided by Steve Fisk,
`fisk@polar.bowdoin.edu'.
The following uses LaTeX to put deleted text in boxes, and new text
in double boxes:
wdiff -w "\fbox{" -x "}" -y "\fbox{\fbox{" -z "}}" ...works nicely.
troff
example.
This example comes from Paul Fox, `pgf@cayman.com'.
Using wdiff
, with some troff
-specific delimiters gives
much better output. The delimiters I used:
wdiff -w'\s-5' -x'\s0' -y'\fB' -z'\fP' ...This makes the pointsize of deletions 5 points smaller than normal, and emboldens insertions. Fantastic! I experimented with:
wdiff -w'\fI' -x'\fP' -y'\fB' -z'\fP'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... Marty Leisner `leisner@eso.mc.xerox.com' says: In the previous example, you had smaller text being taken out and bold face inserted. I had smaller text being taken out and larger text being inserted, I'm using bold face for other things, so this is more clear.
wdiff -w '\s-3' -x'\s0' -y'\s+3' -z'\s0'