grep
Note that grep exists in several variant with different reg exp capabilities. grep -e will use extended reg exp i.e. egrep.
Use -v
when you want to use reg exp for exclude lines.
grep -v X11
It is often useful to print leading and trailing lines around each match. To look for character +
and surrounding lines in man page find
you may do the following.
man find | grep -A5 -B5 +
Grep can also search in many files recursively. E.g. to find all ports using autotools.
cd /usr/ports
grep -iR 'CONFIGURE_STYLE=gnu' *