Question

I am trying to extract a single string out of a line having many segments in a key-value order, but I don’t get it as it matches much more than I want to.

This is my example line:

|SEGA~1~MAGIC~DESCRIPTION~~~M~TEST~|SEGB~34~12.11.2011~3~M~O~|SEGC~HELLO~WORLD~|

This lines is a kind concatenation of many segments into one line. Now I want to extract the the string at index 2 in the segment starting with SEGA.
So what I do is grep for this:

egrep -o 'SEGA(.*?)\~\|'

But it gives me the whole line, sometimes it gives me only the segment I am looking for. With the match I would split that segment by using the ~ character and take the third one.
Since I use .*? with the question mark I expected egrep to only match the content between SEGA and the very first occurrence of ~| which is right before SEGB and not the one at the end of SEGC or SEGB.

How can I tell grep to search for SEGA and give the whole content starting right after SEGA until THE VERY FIRST occurrence of ~|

Answer 1

You can use the -P(–perl-regexp) option in grep:

grep -oP '(?<=SEGA).*?(?=~\|)' file

If you want to include the trailing ~|, please remove the lookahead (?=...).

I think .*? (lazy) does not exit in egrep.