Linux – utility to read environment variables from an env file and then run a command (more lightweight than foreman)

$ num=0
$ declare A_$num=42  # create A_0 and set it to 42
$ echo $A_0
42
$ b=A_$num           # create a variable with the contents "A_0"
$ echo ${!b}         # indirection
42

You can iterate num and use declare to create the variables and indirection to reference them. But wouldn't you really prefer to use arrays?

for i in foo bar baz
do
    some_array+=($i)    # concatenate values onto the array
done

or

string="foo bar baz"
some_array=($string)

How about this?

$ cat IPs
192.168.0.1
192.168.0.2
192.168.0.3
$ cat readips
#!/bin/bash
while read -r ip
do
    IP[count++]=ip                 # is it necessary to save them in an array,
    do_something_directly_with ip  # if you use them right away?
done < IPs

I'm sure someone else has a better answer, but

With "less" after you've opened the file:

G goes to the bottom of the file

^b goes up one page

? searches backwards.

As you said, you can open the file with +G and then use ? and ^b to scroll up. There are likely clever awk things you can do to achieve the same thing in a script.