Comparing C-Strings

Do not use the relational operators (<, ==, etc.) to compare C-strings. Instead, use the library function strcmp(), which compares s1 and s2 lexicographically and returns an integer indicating their relationship:

Zero if the two strings are equal.
Negative if the first string lexicographically precedes the second string. (Lexicographically simply means "in dictionary order").
Positive if the first string lexicographically follows the second string.

To use strcmp() correctly:

Call the function and save the int it returns.
Use the returned value with a relational operator.
Don't treat the return value from strcmp() as a Boolean expression.
Don't repeatedly call strcmp() on the same strings (inefficient).

Here's a quick example. The C-strings s1 and s2 are initialized elsewhere. Since we don't need to modify either argument, we can use "pointer-style" C-strings.

const char *s1 = ..., *s2 = ...;

int result = strcmp(s1, s2);

if (result == 0) ...            // equal
else if (result < 0) ...        // s1 < s2
else ...                        // s1 > s2