CSC161 2010F, Class 10: The Command Line

Overview:
* Command-line basics.
* Using the command line.
* Lab.

Admin:
* Sam not here for office hours.  Will respond to email (I hope).
* Are there questions on assignment 3
  * What do ugly characters like Black Diamond mean?
  * It means that you're dealing with a character outside of 33..127.
* Readings for Tomorrow: 
  * A Tutorial on Binary Numbers (link online)
  * K&R 2.6 and 6.9.
* We may not finish today's lab in class.  
  I expect you to finish it on your own.  
  (You need not do the extra problems.)
* I returned HW2 before class today.  
  Let me know if you have questions on my comments.  
  We'll talk a bit about a variety of issues.
GNU Formatting/Coding Guidelines
* Specify return type
* If you have a non-void return type, you must use "return" at the
  end of the function, even in main, and even if K&R don't.
* Lots of indenting rules and rules for placement of punctuation.

Four score 
                       and 
    seven years ago our fathers brought forth on this continent
a new nation,conceived in liberty                                                          ,and 
dedicated to the proposition
that all men are created equal.

C has at least three "formatting standards".

* Sam will tell you a bit about processing the command line in C and
  then we'll do the lab tomorrow.

* C and Unix grew up hand in hand
* One of the key parts of Unix is that programs take command-line arguments
* So C needs a way for the programmer to access those command-line arguments. 
* Decision in C: Make them parameters to main

int
main (int argc, char *argv[])
{
  return 0;
}

You need not call them argc and argv

int
main (int fred, char *wilma[])
{
  return 0;
}

The integer (argc) parameter is a *count* of the number of arguments
the program was called with.

The array parameter (argv) is the "argument vector" - an array of strings.

If argc is 2, argv[0] and argv[1] are the two arguments.

When you type

% program foo bar baz

Unix/C flils in the argc and argv

How will you use the command-line arguments?
* Eventually: Just like everyone else: For flags and other inputs
* For testing: You can take input from the command line, which is often
  faster.
  * q2l 32.2