String Comparison Operators

Expression	Is True If…
string	string is not null
-n string	The length of string is greater than zero
-z string	The length of string is zero
string1 = string2	string1 and string2 are equal. Single or double
string1 == string2	equal signs may be used. The use of double equal signs is supported by bash and is preferred, but is not POSIX compliant
string1 != string2	string1 and string2 are not equal
string1 > string2	string1 sorts after string2
string1 < string2	string1 sorts before string2 Note: the > and < must be escaped or quoted when used with test or they will be interpreted by the shell as redirect operators.