100 Days of DevOps — Day 52-Conditional Testing in Shell

Welcome to Day 52 of 100 Days of DevOps, Focus for today is Conditional Testing in Bash.

Today I am going to discuss test command

test - check file types and compare values

• In your script you generally see, it starts with left bracket( [ ) when need to perform some testing.

Exit Status

• In bash after running any command, the exit status is returned and stored in variable $?

0 --> good
1 or some other code --> issue

Test Integers

# test 1 -eq 1;echo $?
0

• Here we are trying to check if 1 is equal to 1 and then perform command chaining to merge two command
• As mentioned above exit status 0 mean good

# test 1 -eq 2;echo $?
1

• Exit status other than zero, in the above case, means some issue
• The same way we can test less than or greater than or not equal to

# less then
# test 1 -lt 2;echo $?
0
OR
# greater then
# test 1 -gt 2;echo $?
1
# not equal to
OR 
# test 1 -ne 2;echo $?
0