Removing lines from a file that don't match a pattern using sed

Question

I want to remove all the lines from a file that don't have the form:

something.something,something,something

For example if the file was the following:

A sentence, some words  
ABCD.CP3,GHD,HDID  
Hello. How are you?  
A.B,C,D  
dbibb.yes,whoami,words

I would be left with:

ABCD.CP3,GHD,HDID  
A.B,C,D  
dbibb.yes,whoami,words

I have tried to branch to the end of the sed script if I match the pattern I don't want to delete but continue and delete the line if it doesn't match:

cp $file{,.tmp}
sed "/^.+\..+,.+,.+$/b; /.+/d" "$file.tmp" > $file
rm "$file.tmp"

but this doesn't seem to have any affect at all.

I suppose I could read the file line by line, check if matches the pattern, and output it to a file if it does, but I'd like to do it using sed or similar.

It's working in [DEMO](http://regex101.com/r/hO5rO8/1) – Braj Aug 19 '14 at 12:51 — Braj, Aug 19 '14 at 12:51

score 4 · Accepted Answer · answered Aug 19 '14 at 12:53

4

You can use grep successfully:

grep -E '^[^.]+\.[^,]+,[^,]+,[^,]+$' file > temp
mv temp file

answered Aug 19 '14 at 12:53

hjpotter92

78,589
36
144
183

This is the solution I have used. I was focused too much on using sed to think of using grep. Simple and it works, thanks. – Jxek Aug 19 '14 at 13:04
grep is simpler but for inline edit it would be better if you prefer sed. – Avinash Raj Aug 19 '14 at 13:06

score 4 · Answer 2 · answered Aug 19 '14 at 12:56

4

grep -E '^[^.]+\.[^.]+(,[^,]+){2}$'

answered Aug 19 '14 at 12:56

Kent

189,393
32
233
301

score 3 · Answer 3 · edited Aug 19 '14 at 13:08

Instead of deleting the lines which didn't satisfies the pattern, you could print the lines that matches this something.something,something,something pattern.

Through sed,

$ sed -n '/^[^.]*\.[^,]*,[^,]*,[^,.]*$/p' file
ABCD.CP3,GHD,HDID  
A.B,C,D  
dbibb.yes,whoami,words

Use inline edit option -i[suffix] to save the changes made.

sed -ni.bak '/^[^.]*\.[^,]*,[^,]*,[^,.]*$/p' file

Note: -i[suffix] make a backup if suffix is provided.

Through awk,

$ awk '/^[^.]*\.[^,]*,[^,]*,[^,.]*$/{print}' file
ABCD.CP3,GHD,HDID  
A.B,C,D  
dbibb.yes,whoami,words

Removing lines from a file that don't match a pattern using sed

3 Answers3

Through sed,

Through awk,