UNIX for Dummies Questions & Answers

Hi everybody

I'm trying to use diff to find the differences between two files and show the section of the file where the difference occurred. Diff allows you to use a regular expression to mark the last section header before the difference with the -F flag. That's all fine.

My problem is is that only the first 40 characters of the section lines are shown. Most of my section headers are longer than that (100 characters+) and I would like to be able to see it all, especially since some sections begin the same.

Input:
diff -F [[] -u file1 file2
Output:
@@ -1, 1 +1, 1 @@ [FILE1-CHAPTER-1-SECTION-1-HEADER-MORE-T

The full line should read [FILE1-CHAPTER-1-SECTION-1-HEADER-MORE- THAN-FORTY-CHARACTERS. The line is just an example, the actual headers are more meaningful and cant be reduced to less than 40 chars.

The diff manual says I can use more than one regex for such lines. Can anybody give me an example... Or suggestions... Thanks

It looks like you have GNU diff. In info you will see
You can specify the number of characters in a changed line this way, it is very much like a printf format string - the "for LETTER" bit refers to the line type