Which SAS function would you use to find the length of a character string?

The LENGTH function in SAS is specifically designed to return the length of a character string. It calculates the number of characters in the given string, including spaces, which is crucial for various operations, such as data manipulation and validation tasks.

Using the LENGTH function is straightforward; you simply pass the character variable or string to it, and it outputs the corresponding length. This functionality is particularly useful when you're performing data processing where understanding the size of a string is important, such as when you need to truncate data or allocate memory for output operations.

Other choices like CHARLENGTH, STRLEN, and STRINGLENGTH do not exist as standard SAS functions, which is why they would not perform the required operation successfully. The availability and correctness of the LENGTH function make it the appropriate choice for finding the length of a character string in SAS.