-eq
equal to for numbers
==
equal to for letters
-ne
not equal to
!==
not equal to for letters
-lt
less than
-le
less than or equal to
-gt
greater than
-ge
greater then or equal to
The if statement as the following syntax:
if commands; then
commands
[elif commands; then
commands...]
[else
commands]
fiWhat is $?:
Exit status 0-255
Exit status 0
0 indicates success
Exit status 1
Any exit status other than 0 means failure