Programming Fundamentals

Write a program called command_line_words.c that takes in comand line arguments and prints out the total number of words that appear in them.

A word is defined as any collection of characters that do not contain a space. For example, "Today I Slept" contains 3 words by that definition.

However, the twist with this exercise is that we are going to input command line arguments in a special way such that a single argument can contain spaces.

So far, we have seen the use of command line arguments as such:

    ./program Here are my arguments

We know that argc in this case is 5. We can also visualise the layout of argv like so:

However, there is actually a way to group words together into a single argument! This can be done by surrounding these words in double quotes. If we adjust the above example to instead be:

    ./program Here "are my" arguments

Then argc will now be 4. We can also visualise the new layout of argv like so:

It is important to see here that the number of command line arguments changes, but the number of words stays the same (4, excluding ./program)!

Here are some examples for how your program should work (Note that we ignore ./command_line_words in all outputs):

./command_line_words Here "are my" arguments
There are 3 command line arguments (Excluding program)!
There were 4 total words!
./command_line_words "All words in one argument"
There are 1 command line arguments (Excluding program)!
There were 5 total words!
./command_line_words "Mixture of" "words" in "Command line arguments"
There are 4 command line arguments (Excluding program)!
There were 7 total words!
./command_line_words "Empty Arguments" " " " " "End"
There are 4 command line arguments (Excluding program)!
There were 3 total words!

Hints, Notes and Assumptions

• You will only be given letters, quotes and spaces as input
• Autotests will use single quotes to group arguments. There is no fundamental difference in this exercise between using single and double quotes.

When you think your program is working, you can use autotest to run some simple automated tests:

1511 autotest command_line_words

Download valid_c_brackets.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/valid_c_brackets.c .

Your task is to add code to these functions in valid_c_brackets.c:

// Given a string containing the contents of a C file, print out whether it has
// correct matching brackets. If it does not, print out which line that didn't
// have a correct matching bracket.
void valid_c_brackets(char *file_contents) {
    // TODO: COMPLETE THIS FUNCTION AND REMOVE THE PRINTF BELOW
    printf("valid_c_brackets() has not been implemented yet.\n");
}

In this program you will provide the name of a C file in the command line arguments and the program will print whether it has valid matching brackets.

When we compile our code, the compiler (dcc in our case) will check if your code is correct before it does so and prints errors if it cannot compile. One thing a compiler will check for is if all your brackets match properly.

This can get quite complex when you have brackets nested in other brackets (such as putting a while loop inside an if statement where we print out an array)

In this program, we have handled all file input and you have the write the provided function to test bracket matching. In the function, you will be provided the file contents as a string so that you do not need to worry about the file aspect

Some example files are provided for you below which you can download to use. Make sure they are in the same directory as valid_c_brackets.c when you are testing

Example files

Download basic_valid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/basic_valid.c .

Download basic_invalid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/basic_invalid.c .

Download medium_valid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/medium_valid.c .

Download medium_invalid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/medium_invalid.c .

Download complex_valid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/complex_valid.c .

Download complex_invalid.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1511/23T1/activities/valid_c_brackets/files/complex_invalid.c .

Here is some example outputs using some of these files.

./valid_c_brackets basic_valid.c
File has valid matching brackets!
./valid_c_brackets basic_invalid.c
Non-matching bracket found on line 5. Was expecting a ')' but got a '}'
./valid_c_brackets medium_valid.c
File has valid matching brackets!
./valid_c_brackets medium_invalid.c
There was a missing '}' bracket in this program

There are essentially 3 cases here.

• File is valid - Print as such
• Non-matching brackets - When searching for a match to an opening bracket, a non-matching closing bracket was found first
• Not enough brackets - The end of the file was reached and the last seen, non-matched opening bracket was never matched.

The key idea with this exercise is that you need to consider the most recent opening bracket and try to match it before matching other un-matched opening brackets before it.

Hints, Assumptions and Notes

• How could you use a stack to model this problem?
• You can assume that the only bracket pairs you need to match are:
  • ()
  • {}
  • []
• You can assume these brackets will only appear in actual code, meaning they can't appear in comments or strings (such as printing the bracket)
• You will need to keep track of the current line. This can simply be done by looking for each new line character in the given string.
• As a note from the above, there can still appear new line characters in the file such as in printfs, but this will appear as 2 characters in the string so you do not need to worry about it (since actual new lines are 1 character)

When you think your program is working, you can use autotest to run some simple automated tests:

1511 autotest valid_c_brackets