Make diff Use Full Terminal Width in Side-by-Side Mode

diff()terminal

Most applications are smart about using the full width of the terminal available to them. My shell does, screen, vim, etc. However, diff in side-by-side mode (-y), does not. This angers me. It uses 126 character width, which is not even half of my 270 block width terminal.

Looking through the man page does not reveal anything particular about automatically adjusting the width, only manually specifying it via -W.

Is there perhaps a "hidden feature" of diff to allow it to automatically expand to the full width of the terminal?
Or;
What is the easiest path to automatically inserting -W <terminalsize> into my diff command whenever I run it?

I am under the assumption that automatically appending -W to everything couldn't hurt anything, because it will only ever mean "use $x columns", which is always what I want, whether I'm in side-by-side mode, or otherwise.

Best Answer

$ alias diff='diff -W $(( $(tput cols) - 2 ))'

ought to do it. You'll want to add it to ~/.bashrc as well.

The - 2 is mainly paranoia, in case something (embedded double-width Unicode?) expands enough to make the line wrap; if you want, you can just use

$ alias diff='diff -W $(tput cols)'

Related Solutions

How to make and apply (patch) one side diff

As Gilles says, you'll need to use a tool that knows about the format of your config files. For your particular example, you can use a short Python script that uses the built-in ConfigParser module.

First, let's say your original configuration file on the server is original.cfg:
```
[config]
ip=127.0.0.1
port=22
```
Now put your changes in a new file called update.cfg:
```
[config]
user=root
```
This file should have new or changed entries listed under the section heading where you would like them to go.

Then run a script like this one:

#!/usr/bin/env python

import ConfigParser

config = ConfigParser.ConfigParser()

# Read the original config file
with open('original.cfg', 'r') as f:
    config.readfp(f)

# Also read in all the changes we'd like to make
with open('update.cfg', 'r') as f:
    config.readfp(f)

# Write the full new config file out
with open('output.cfg', 'w') as f:
    config.write(f)

There are, of course, plenty of variations on how to do this. For example, the config changes could be coded directly into the Python script rather than read from a separate update.cfg file. This should give you a good base to get started, though.

Diff Tool – How to Print Full File Diff When File is Missing

With at least some versions of GNU diffutils' diff, you can use the -N flag to do that directly (although the documentation appears to say that only works for directory diffs).

$ ls
foo
$ cat foo
foo
$ diff -u foo bar
diff: bar: No such file or directory
$ diff -uN bar foo
--- bar 1970-01-01 01:00:00.000000000 +0100
+++ foo 2012-09-04 12:45:34.000000000 +0200
@@ -0,0 +1 @@
+foo
$ diff -uN foo bar
--- foo 2012-09-04 12:45:34.000000000 +0200
+++ bar 1970-01-01 01:00:00.000000000 +0100
@@ -1 +0,0 @@
-foo
$ diff -v
diff (GNU diffutils) 2.8.1
Copyright (C) 2002 Free Software Foundation, Inc.

Best Answer

Related Solutions

How to make and apply (patch) one side diff

Diff Tool – How to Print Full File Diff When File is Missing

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