eval is to interpret and execute dynamic or complex commands stored in strings or variables

syntax

$ eval [arguments]

To Store Command in a Variable

$ var="free -h"

$ eval "$var"

To substitute command

$ command="echo \$(uptime)"

$ eval "$command"

To generate and execute commands inside a loop dynamically

$ vim newscript.sh
#!/bin/bash
for i in {1..10}; do
  eval "echo 'Loop iteration $i'"
done

:x save and exit