Question

str is of the following pattern:

1 abc (1 <something>)

For example:

1 abc (1 hello)
1 abc (1 shalom)
1 abc (1 hola)

How could I extract <something> from str using egrep?

Answer 1

If you want to extract just the <something> then I’d suggest grep -P (perl regex):

grep -P -o '(?<=\(1 ).*?(?=\))' INPUTFILE

The -o returns just the matched portion being <something>. The regex looks for text preceded by (1 and followed by ).

You wouldn’t be able to do that with egrep as it doesn’t support lookarounds. The best you’d do is extract the (1 <something>) with:

egrep -o '\(1 (.*)\)' INPUTFILE

[foo@bar ~]$ grep -P -o '(?<=\(1 ).*?(?=\))' INPUTFILE
hello
shalom
hola

[foo@bar ~]$ egrep -o '\(1 (.*)\)' INPUTFILE
(1 hello)
(1 shalom)
(1 hola)