A linux script for finding a port number according to a service (e.g. http: 80)

port by service

#!/bin/bash

# This one displays both service and port number colored in red (most likely):

egrep --color -o -m 1 '^'$1' *[0-9]+' /etc/services 

# This one displays only the port number:

egrep -o -m 1 '^'$1'\s+[0-9]+' /etc/services | grep -P -o '\d+$'

# or

egrep -o -m 1 '^ftp\s+[0-9]+' /etc/services | egrep -o '[1-9]+$'