:   '''string compare''' ''?'''''-nocase'''''? ?'''''-length int'''''? string1 string2''

Perform a character-by-character comparison of strings ''string1'' and ''string2''.
Returns '''-1''', '''0''', or '''1''', depending on whether ''string1'' is lexicographically less than, equal to, or greater than ''string2''.
If '''-length''' is specified, then only the first ''length'' characters are used in the comparison.
If '''-length''' is negative, it is ignored.
If '''-nocase''' is specified, then the strings are compared in a case-insensitive manner.

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Returns -1, 0, or 1, depending on whether ''string1'' is lexicographically less than, equal to, or greater than ''string2''. Options are ''-nocase'' or ''-length integer''. (From the Tcl/Tk Reference Guide)

"Lexicographically less, equal, or greater" means in terms of ASCII values. The less the ASCII value, the less the character is lexicographically.

Basically it means: '''. < 0 < 1 < 2 < ... < 9 < A < B < ... < Z < a < b < ... < z'''

The command compares the strings character by character beginning at the left side
(i.e. the first character) until it either finds a difference or the end of the shortest string.

For example:

   string compare "abc" "xyz"

would return a -1, because "a" is less than "z" in ASCII.

   string compare "abcd" "abc"

would return a 1 - the first string is 'greater' than the second because it is longer.

What about

   string compare "3" "10"

While one might be tempted to say "well, 3 is less than 10, so it will return a -1",
the true answer is that the above returns a "1" - because lexicographically, 3 comes after 1.
This is a reason NOT to use string compare if the arguments may both be numeric a
nd you want to know when one is truly less than the other.

The ''-nocase'' option ignores the case of the two strings as they are compared.

The ''-length NUMBER'' compares only the first NUMBER of characters.
Note that this value is '''one''' based.
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**See also**
   * [string]

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