I wonder is there any program that can take a bash script as input and print out all bash commands it will run? A program that would unroll loops, expand environment variables and generally not perform any destructive action nor call any external binaries. It’s like a dry run of sorts.

Edit: I’ve created a script that updates ufw rules. I wanted to use multiple IP addresses as a range and multiple interfaces like this:

ufw add limit in on eth0,eth1 from 172.16.0.0/12,10.0.0.0/8,192.168.0.0/16 to any port 22 comment "allow SSH on LAN"

but ufw does not support setting multiple interfaces and multiple interfaces comma separated like ports so I created a script instead.

# ...
lan_ip_range=('172.16.0.0/12' '10.0.0.0/8' '192.168.0.0/16')
for ip_lan in "${lan_ip_range[@]}"; do
	# SSH
	ufw add limit in on eth0 from "$ip_lan" to any port 22 comment "allow SSH on LAN"
	ufw add limit in on eth1 from "$ip_lan" to any port 22 comment "allow SSH on LAN"
# ...
	done

I want to make sure it does what I expect it to do. so expected output should be something like this:

ufw add limit in on eth0 from 172.16.0.0/12 to any port 22 comment "allow SSH on LAN"
ufw add limit in on eth0 from 10.0.0.0/8 to any port 22 comment "allow SSH on LAN"
ufw add limit in on eth0 from 192.168.0.0/16 to any port 22 comment "allow SSH on LAN"
  • Agility0971OPEnglish
    2•2 years ago

    yes, I could do that but If I ever would check some other script this way, a script I didn’t write my self, then I would need to edit that as well. I’m now thinking of something like a container that runs a script and replaces command not found errors with an echo of the command in question.