Learning Linux Shell Scripting - Second Edition

String comparison options for the test command

The following is a summary of various options for string comparison using test, which is taken from the Bash reference manual available at http://www.gnu.org/software/bash/:

Test operator	Tests true if
-n string	True if the length of string is non-zero.
-z string	True if the length of string is zero.
string1 != string2	True if the strings are not equal.
string1 == string2 string1 = string2	True if the strings are equal.
string1 > string2	True if string1 sorts after string2 lexicographically.
string1 < string2	True if string1 sorts before string2 lexicographically.

If we want to check whether the length of a string is non-zero, then we can check it ...