Can't use SED for extracting value

glestwid · 05-19-2019, 04:37 PM

Hi,

I am trying to use SED for printing specific groups from my CSV file per this Stackexchange post. Here's the command:

Code:

sed -e 's/^(\d+);infrastructure;[^;]*;.+/\1/g' 13-05-2019.csv

But instead of the group value I get this:

Quote:

sed: -e expression #1, char 37: invalid reference \1 on `s' command's RHS

What am I doing wrong? How to write this expression with SED in a correct way?

syg00 · 05-19-2019, 06:23 PM

Don't believe everything you read on the net - although there are some good points in that thread.
For backreferences I think you'll need extended regex - see the manpage.
That will solve this particular issue.

berndbausch · 05-19-2019, 06:53 PM

The “\1” in the replacement part of the sed substitution command requires a “\(somexregexp\)” in the search part.

Code:

sed ‘s/\(somethingorother\)blabla/\1blublu/‘

EDIT: According to section 5.4 in the sed manual, simple parentheses without the backslash are used if you switch on extended regular expression using the -E option. Given all the plus signs in your sed command, I guess that this is your intention anyway.

grail · 05-20-2019, 09:35 AM

Further to what has already been said, you will need -r (extended regex) for the + to work as expected as well

You may also wish to show some input and expected output as someone may also have a better idea / method