I need to figure out a regular expression to delete all lines that do not begin with either "+" or "-".
I want to print a paper copy of a large diff file, but it shows 5 or so lines before and after the actual diff.
A:
diff -u <some args here> | grep '^[+-]'
Or you could just not produce the extra lines at all:
diff --unified=0 <some args>
Ether
2009-11-12 20:50:39
useless use of `cat`: `sed` accepts filenames as arguments
Dennis Williamson
2009-11-12 22:13:51
Agree for this particular case. I typically use cat when using a long chain of sed commands to incrementally filter out data. If I have too big a data file to begin with, I replace cat with head -100 and the remaining part stays the same.
Joy Dutta
2009-11-12 22:42:02
+8
A:
In VIM:
:g!/^[+-]/d
Here is the English translation:
globally do something to all lines that do NOT! match the regular expression: start of line^ followed by either + or -, and that something to do is to delete those lines.
Marcin
2009-11-12 20:53:04
if you want to save one keystroke: ':v' is a synonym to ':g!' :)
Leonardo Constantino
2009-11-13 17:21:13
A:
egrep "^[+-]" difffile >outputfile
Instead of deleting everything that doesn't match you show only lines that match. :)
Muxecoid
2009-11-12 20:53:19
You definitely need another caret and may not need "e" or quotes. This works for me: `grep ^[^+-]`
Dennis Williamson
2009-11-12 22:17:32
A:
If you need to do something more complex in terms of regular expressions, you should use this site: http://txt2re.com/
it also provides code examples for many different languages.
Arthur Frankel
2009-11-12 20:53:56