Bash Shell Script - Check for a flag and grab its value

Question

I am trying to make a shell script which is designed to be run like this:

script.sh -t application

Firstly, in my script I want to check to see

Answer 1

Use $# to grab the number of arguments, if it is unequal to 2 there are not enough arguments provided:

if [ $# -ne 2 ]; then
   usage;
fi

Next, check if $1 equals -t, otherwise an unknown flag was used:

if [ "$1" != "-t" ]; then
  usage;
fi

Finally store $2 in FLAG:

FLAG=$2

Note: usage() is some function showing the syntax. For example:

function usage {
   cat << EOF
Usage: script.sh -t 

Performs some activity
EOF
   exit 1
}