[SOLVED] sed: remove lines from a text file not containing parentheses

shusai · 09-16-2013, 02:43 PM

I want to delete lines from a text file which do not contain parentheses, e.g.:

This is the first line.
This is (123) another line.
Another line.
One more (useless) line.

The result should be:

This is (123) another line.
One more (useless) line.

I found out that

Code:

sed '/(/!d' file > output

should do what I want, but it gives me an empty file.

How can I delete lines NOT containing parentheses?
Thank you for your help!

suicidaleggroll · 09-16-2013, 03:20 PM

Personally, I would just grep for parenthesis and toss it into a new file. Something like

Code:

grep "(" file > newfile

Unless there's some reason this wouldn't work for you.

kabamaru · 09-16-2013, 03:29 PM

There are many ways you can do this. The thing is, your command _should_ work (works fine here). Do you by any chance use the same file as input, as well as output? If that's the case, yes your file's contents will just get erased. So, either you choose an output file other than the input file, or edit the original file in place (generally unsafe) with:

Code:

sed -i '/(/!d' file

jpollard · 09-16-2013, 10:36 PM

Quote:

Originally Posted by shusai

I want to delete lines from a text file which do not contain parentheses, e.g.:

This is the first line.
This is (123) another line.
Another line.
One more (useless) line.

The result should be:

This is (123) another line.
One more (useless) line.

I found out that

Code:

sed '/(/!d' file > output

should do what I want, but it gives me an empty file.

How can I delete lines NOT containing parentheses?
Thank you for your help!

Try "grep '(' file >output". No real need for sed.

shusai · 09-17-2013, 11:04 AM

Thank you all for your help, both the grep and sed with -i work!