Invoking the function in bash does not give the proper result - bash

Question

I took the code from this nice article: https://catonmat.net/tcp-port-scanner-in-bash
It uses the function scan. When I copy the code, it doesn't work for me.
I had similar issues with bash functions before and could not find the solution either.
I try to invoke the function this way directly in the script:
#!/bin/bash
scan() {
if [[ -z $1 || -z $2 ]]; then
echo "Usage: $0 <host> <port, ports, or port-range>"
return
fi
local host=$1
local ports=()
case $2 in
*-*)
IFS=- read start end <<< "$2"
for ((port=start; port <= end; port++)); do
ports+=($port)
done
;;
*,*)
IFS=, read -ra ports <<< "$2"
;;
*)
ports+=($2)
;;
esac
for port in "${ports[#]}"; do
alarm 1 "echo >/dev/tcp/$host/$port" &&
echo "port $port is open" ||
echo "port $port is closed"
done
}
scan
I also tried $(scan) - did not work as well.
The result - it does not want to scan anything ( I think there is something I should run in order to invoke the function - the code seems fine):
$ ./scan.sh google.com 22-99
Usage: ./scan.sh <host> <port, ports, or port-range>
$ ./scan.sh scan google.com 22-99
Usage: ./scan.sh <host> <port, ports, or port-range>
What am I missing? It is not the first time I've had a similar problem.
P.S. As was already suggested, scan "$1" "$2" did the job alright. However, now I encountered a similar issue when invoking this function from a different function:
function dosmth {
while test $# -gt 0; do
case "$1" in
-t)
shift
scan "$1" "$2"
shift
;;
*)
exit 1
;;
esac
done
}
dosmth $1
I also tried dosmth "$1" "$2" - the issue persists.
Right now dosmth function works alright but scan has the similar result as before it does not scan anything.
$ ./dosmt.sh -t google.com 80
Usage: -t ./dosmt.sh <host> <port, ports, or port-range>
My solution may help somebody - I changed to:
dosmth "$1" "$2" "$3"

Answer 1

If function run from a script, you need to pass args from script to the function
...
scan "$1" "$2"
Same goes when function run from another function, you have to pass args from "parent" function to "child" function.
fun1() {
echo "fun1 $1 $2"
}
fun2() {
fun1 "$1" "$2"
}
fun2 "$1" "$2"
Also it's a good practice to create vars with appropriate names from this args($1, $2, $3 ...) to use in functions.
#!/bin/bash
script=$0
host=$1
port_range=$2
ports=()
scan() {
if [[ -z $host || -z $port_range ]]; then
echo "Usage: $script <host> <port, ports, or port-range>"
return
fi
case $port_range in
*-*)
IFS=- read start end <<< "$port_range"
for ((port=start; port <= end; port++)); do
ports+=($port)
done
;;
*,*)
IFS=, read -ra ports <<< "$port_range"
;;
*)
ports+=($port_range)
;;
esac
for port in "${ports[#]}"; do
alarm 1 "echo >/dev/tcp/$host/$port" &&
echo "port $port is open" ||
echo "port $port is closed"
done
}
scan