Ungroup diff's output

Question

I've got two files, and output of diff looks like this:

33428,33429c33428,33429
< lucid-security|main|icedtea-6-jre-cacao|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|icedtea6-plugin|6b20-1.9.2-0ubuntu1~10.04.1
---
> lucid-security|main|icedtea-6-jre-cacao|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|icedtea6-plugin|6b20-1.9.4-0ubuntu1~10.04.1
33835,33842c33835,33842
< lucid-security|main|openjdk-6-dbg|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-demo|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-doc|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jdk|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre-headless|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre-lib|6b20-1.9.2-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-source|6b20-1.9.2-0ubuntu1~10.04.1
---
> lucid-security|main|openjdk-6-dbg|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-demo|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-doc|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jdk|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre-headless|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre-lib|6b20-1.9.4-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-source|6b20-1.9.4-0ubuntu1~10.04.1
34182c34182
< lucid-security|universe|openjdk-6-jre-zero|6b20-1.9.2-0ubuntu1~10.04.1
---
> lucid-security|universe|openjdk-6-jre-zero|6b20-1.9.4-0ubuntu1~10.04.1

I would like to "ungroup" the output, so the old line is followed by the new line. Could be looking like this:

< lucid-security|main|icedtea-6-jre-cacao|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|icedtea-6-jre-cacao|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|icedtea6-plugin|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|icedtea6-plugin|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-dbg|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-dbg|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-demo|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-demo|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-doc|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-doc|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jdk|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jdk|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre-headless|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre-headless|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-jre-lib|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-jre-lib|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|main|openjdk-6-source|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|main|openjdk-6-source|6b20-1.9.4-0ubuntu1~10.04.1
< lucid-security|universe|openjdk-6-jre-zero|6b20-1.9.2-0ubuntu1~10.04.1
> lucid-security|universe|openjdk-6-jre-zero|6b20-1.9.4-0ubuntu1~10.04.1

I don't need the information about position of changed lines, and I don't even care about lines added or deleted in second file. Just this quick compare of changes.

Answer 1

A quick regex can nicely sort out which lines are prefixed by a given character.

diff file1 file2 | egrep '^[<>]' > output.txt

That should leave you with just positive and negative changes, no line numbers, no separators.