Chapter 9, Problem 4E

Write a function called s to extract a portion of a character string. The function should be called as follows:

s

where S is the character string from which you are extracting the substring, S is an index number into S indicating the first character of the S, c is the number of characters to be extracted from the S string, and r is an array of characters that is to contain the extracted substring.

For example, the call

s

extracts the substring̎ (three characters starting with character number 4) from the string̎ and places the result in r.

Be certain the function inserts a null character at the end of the substring in the result array. Also, have the function check that the requested number of characters does, in fact, exist m the string. If this is not the case, have the function end the substring when it reaches the end of the source string. So, for example, a call such as

s

should just place the string “words” inside the result array, even though 20 characters were requested by the call.