How can I delete all lines that do not begin with certain characters?

Question

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.

Why can't you just regenerate the diff and tell it to reduce the # of context lines? — JSBձոգչ, Nov 12 '09 at 20:50

Marcin · Accepted Answer · 2009-11-12T20:59:29.173

73

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.

edited Nov 12 '09 at 20:59

answered Nov 12 '09 at 20:53

Marcin

12,245
9
42
49

6

if you want to save one keystroke: ':v' is a synonym to ':g!' :) – Cyber Oliveira Nov 13 '09 at 17:21
That saves two keystrokes! Shift, 1. Neat. – Marcin Nov 13 '09 at 20:35
1

Although the answer is spot on, the original question was not vim specific. As reference, one can, however, do exactly the same with sed (`sed -e 'g!/^[+-]/d'`). – h7r Dec 20 '14 at 21:29

score 2 · Answer 2 · answered Nov 12 '09 at 20:50

2

sed -e '/^[^+-]/d'

answered Nov 12 '09 at 20:50

ennuikiller

46,381
14
112
137

score 0 · Answer 3 · answered Nov 12 '09 at 20:50

0

diff -u <some args here> | grep '^[+-]'

Or you could just not produce the extra lines at all:

diff --unified=0 <some args>

answered Nov 12 '09 at 20:50

Ether

53,118
13
86
159

score 0 · Answer 4 · answered Nov 12 '09 at 20:51

0

cat your_diff_file | sed '/^[+-]/!D'

answered Nov 12 '09 at 20:51

Joy Dutta

3,416
1
19
19

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 Nov 12 '09 at 22:42

score 0 · Answer 5 · answered Nov 12 '09 at 20:53

0

egrep "^[+-]" difffile >outputfile

Instead of deleting everything that doesn't match you show only lines that match. :)

answered Nov 12 '09 at 20:53

Muxecoid

1,193
1
9
22

1

You definitely need another caret and may not need "e" or quotes. This works for me: `grep ^[^+-]` – Dennis Williamson Nov 12 '09 at 22:17

score 0 · Answer 6 · answered Nov 12 '09 at 20:53

0

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.

answered Nov 12 '09 at 20:53

Arthur Frankel

4,695
6
35
56

score 0 · Answer 7 · answered Mar 10 '17 at 09:06

%!grep -Ev '^[+-]'

does it inline on current file, and can be considerably faster than :v for large files.

Tested on Vim 7.4, Ubuntu 14.04, 1M line log file.

Lines that don't contain word: https://superuser.com/questions/265085/vim-delete-all-lines-that-do-not-contain-a-certain-word/1187212#1187212

How can I delete all lines that do not begin with certain characters?

7 Answers7