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After you've used diff for a while, the output is easy to read. Sometimes, though, it's just easier to see two files side-by-side. The sdiff command does that. Between the files, it prints < to point to lines that are only in the first file, > for lines only in the second file, and | for lines that are in both, but different. By default, sdiff shows all the lines in both files. Here's a fairly bogus example that compares two files that contain the output of who (Section 2.8) at different times:
$ sdiff -w75 who1 who2
jake vt01 Sep 10 10:37 jake vt01 Sep 10 10:37
uunmv ttyi1i Sep 16 11:43 <
jerry ttyi1j Sep 15 22:38 jerry ttyi1j Sep 15 22:38
jake ttyp1 Sep 9 14:55 jake ttyp1 Sep 9 14:55
jake ttyp2 Sep 9 15:19 | ellen ttyp2 Sep 16 12:07
> carolo ttyp5 Sep 16 13:03
alison ttyp8 Sep 9 12:49 alison ttyp8 Sep 9 12:49To see only lines that are different, use -s (silent):
$ sdiff -s -w75 who1 who2
2d1
uunmv ttyi1i Sep 16 11:43 <
5c4,5
jake ttyp2 Sep 9 15:19 | ellen ttyp2 Sep 16 12:07
> carolo ttyp5 Sep 16 13:03The output lines are usually 130 characters long. That's too long for 80-column-wide screens; if you can put your terminal in 132-column mode or stretch your window, fine. If you can't, use the -w option to set a narrower width, like -w80 for 80-column lines; sdiff will show the first 37 characters from each line (it doesn't write quite all 80 columns). If you can set your printer to compressed type or have a very wide window, use an option like -w170 to get all of each line.
Section 11.5 explains a very useful feature of sdiff: building one file interactively from two files you compare.
-- JP
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| 11.3. Context diffs |  | 11.5. Choosing Sides with sdiff |
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