Bash getops - Quick & Easy

Ever wanted to create this super script with tonns of flags and parameters?
In this short tutorial I will show you how to do it in bash shell.

Let's say we have a script named:script.sh
That has 3 flags (-v for verbouse, -h for help, -i for ip address as input).
The two first parameters do not really get input, but more "tell the script how to behave", while the third parameter actually gets a value from user (ip address).

The "getopts" function is a very handful function when you’re working with script where parameters and flags have to be set.

Our script will be executed as (for example):
#./script.sh -v -i 10.100.1.2

This is the content of our short script:

#!/bin/bash 

usage() {

cat << EOF

-h help

-v verbouse mode

-i new ip address

EOF

} 

while getopts "i:hv" flag ; do
        case $flag in
                i ) IPADDR=$OPTARG;;
                h ) usage;;
                v ) VERB=1;exit 0;;
        esac
done

Pay attention to the options with a colon (“:”) after them need to have an argument set.
Yet if there is no column, then no argument is needed (-h, -v).

We combine while loop with "getopts" function, that will use case to determine which flags were used and what values has been assigned.