0x0A-argc_argv

0x0A. C - argc, argv

In the project, we learn how to receive arguments from the commandline into our main() function.

The declaration of main() now looks like this:

int main(int argc, char *argv[])
{
    ...
}

int argc

This holds the number of arguments passed to your program.

NOTE: It also counts the name of the program along with the number of arguments passed.

You'll see more on this shortly.

char *argv[]

This holds a list of all the argument passed to your program, including the name of the program.

Imagine we have a program named listfiles, we can pass filenames (arguments) to the program by running it like this:

./listfiles file1 file2 file3

Now, inside the main() function of the program...

• argc = 4

• argv = {"./listfiles", "file1", "file2", "file3"}

Look at the tasks below to gain more insight into how you can use these

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0. It ain't what they call you, it's what you answer to

Write a program that prints its name, followed by a new line.

• If you rename the program, it will print the new name, without having to compile it again
• You should not remove the path before the name of the program

solution

1. Silence is argument carried out by other means

Write a program that prints the number of arguments passed into it.

• Your program should print a number, followed by a new line

solution

2. The best argument against democracy is a five-minute conversation with the average voter

Write a program that prints all arguments it receives.

• All arguments should be printed, including the first one
• Only print one argument per line, ending with a new line

solution

3. Neither irony nor sarcasm is argument

Write a program that multiplies two numbers.

• Your program should print the result of the multiplication, followed by a new line
• You can assume that the two numbers and result of the multiplication can be stored in an integer
• If the program does not receive two arguments, your program should print Error, followed by a new line, and return 1

solution

4. To infinity and beyond

• Print the result, followed by a new line
• If no number is passed to the program, print 0, followed by a new line
• If one of the number contains symbols that are not digits, print Error, followed by a new line, and return 1
• You can assume that numbers and the addition of all the numbers can be stored in an int

solution

5. Minimal Number of Coins for Change

Write a program that prints the minimum number of coins to make change for an amount of money.

• Usage: ./change cents
• where cents is the amount of cents you need to give back
• if the number of arguments passed to your program is not exactly 1, print Error, followed by a new line, and return 1
• you should use atoi to parse the parameter passed to your program
• If the number passed as the argument is negative, print 0, followed by a new line
• You can use an unlimited number of coins of values 25, 10, 5, 2, and 1 cent

solution