Bash Scripting: String and Arithmetic operators

String comparison
1. s1 = s2
2. s1 != s2
3. s1 < s2
4. s1 > s2

Arithmetic comparison
1. -lt (<)
2. -gt (>)
3. -le (<=)
4. -ge (>=)
5. -eq (==)
6. -ne (!=)