Grep

General

find all lines NOT containing 'svin' (in[V]erted matching):

$ egrep -v svin

show [O]nly matching parts:

$ egrep -o svin

search for phone number in mails:

$ egrep -hC2 "^[0-9]{8}" ~/.maildir/cur/*
       -h : don't show filenames
       -C2: show 2 lines before and after matched lines (Context)

list all files in current dir and subdirs with IP numbers in them:

$ egrep -rH "(([0-9]{1,3})\.){3}\2" .|less

show match with fancy colouring:

$ egrep --color something

Regular Expressions

egrep uses POSIX 1003.2 regular expressions.

Examples

$ egrep "(svine|grise)hund"

grep

grep uses obsolete regular expressions, which are like POSIX 1003.2 regular expressions, except that ( ) | ? + { } are escaped. standard regex metacharacters:

. * [ ] \? \+ \{ \| \( \)

word matching:

$ grep "\(svine\|grise\)hund"