| 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. |