Bash comparisions

Question 1

Syntax for comparing variable with a value

Answer 1

Always use double quotations with the variable.

e.g. “$myvariable” -eq “this is a string”

This invariably avoids errors. Whereas sometimes quotations are necessary and omitting them generates errors.

Question 2

Zero LENGTH string

Non zero LENGTH string

Answer 2

• z “$mystring”
• nz “$mystring”

Question 3

String equality

String inequality

Numeric equality

Numeric inequality

Numeric less than

Numeric less or equal

Numeric greater than

Numeric greater or equal

Answer 3

“abc” =“$mystring”

“abc” !=“$mystring”

3 -eq“$mystring”

3 -ne“$mystring”

3 -lt“$mystring”

3 -le“$mystring”

3 -gt“$mystring”

3 -ge“$mystring”

Question 4

Exists and is a regular file

Exists and is a directory

1st file newer than second file

1st file older than second file

Answer 4

-f“$myfile”

-d“$mydir”

“$myfile” -ot./bashrc

“$myfile” -nt./bashrc