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601: Mainline

Now that you know how to supply a command-line file name, you probably want to know how to supply other command-line arguments as well. In particular, you probably will want to know how to supply and make use of command-line arguments that determine exactly what your program is to do, given several slightly different options.

Suppose, for example, that you want a version of analyze_trades that examines a specified trade file, computing either the average price-per-share paid, or the average number of shares traded, or both. Following the conventions of Unix, you probably would want your program to accept an option-specifying character called a flag, marked as such by a hyphen. You would want your program to recognize the following indication that it is to compute average price:

                *-- Indicates program is to compute average price 
                v 
analyze_trades -p test.data 

Similarly, your program should recognize the following indication that it is to compute the average number of shares traded:

                *-- Indicates program is to compute average number 
                | 
                v 
analyze_trades -n test.data