Parentheses in regex - subexpressions example

By placing part of a regular expression inside round brackets or parentheses ( and ), you can group that part of the regular expression together.

In previous example the regexp won't match /dev/tty0p0 and /dev/ttyS0. To fix this use the following regex:

egrep '/dev/(([a-z]|[A-Z])*[0-9]?)*' /etc/sane.d/dc25.conf

Output:

port=/dev/ttyS0
#port=/dev/ttyd1
#port=/dev/tty0p0
#port=/dev/tty01