Linux – Shell script to change uid for user

Do you mean

tail -f logfile.log

?

(Man page for tail)

$ 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