16.3.4 String tests
These options test string characteristics. You may need to quote
string arguments for the shell. For example:
test -n "$V"
The quotes here prevent the wrong arguments from being passed to
test if ‘$V’ is empty or contains special characters.
- ‘-z string’
- True if the length of string is zero.
- ‘-n string’
- ‘string’
- True if the length of string is nonzero.
- ‘string1 = string2’
- True if the strings are equal.
- ‘string1 == string2’
- True if the strings are equal (synonym for =).
- ‘string1 != string2’
- True if the strings are not equal.