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Resources

Read or watch:

Additional Resources

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

  • How to use arguments passed to your program
  • What are two prototypes of main that you know of, and in which case do you use one or the other
  • How to use __attribute__((unused)) or (void) to compile functions with unused variables or parameters

Requirements

General

  • Allowed editors: vi, vim, emacs
  • All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89
  • All your files should end with a new line
  • A README.md file, at the root of the folder of the project is mandatory
  • Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
  • You are not allowed to use global variables
  • No more than 5 functions per file
  • The prototypes of all your functions and the prototype of the function _putchar should be included in your header file called main.h
  • Don’t forget to push your header file
  • You are allowed to use the standard library

Quiz questions

Question #0

What is argc?

  • The length of the first command line argument

  • The number of command line arguments

  • A flag set to 1 when command line arguments are present

  • The size of the argv array

Question #1

What is argv[argc]?

  • The last command line argument

  • NULL

  • It does not always exist

  • The program name

  • The first command line argument

Question #2

What is argv?

  • An array containing the program compilation flags

  • An array containing the program command line arguments

  • An array of size argc

Question #3

What is argv[0]

  • The program name

  • NULL

  • It does not always exist

  • The first command line argument

Question #4

In the following command, what is argv[2]?

$ ./argv My School is fun

  • My School is fun

  • NULL

  • fun

  • ./argv

  • My School

  • is

  • School

  • is fun

  • My

Question #5

In the following command, what is argv[2]?

$ ./argv "My School is fun"

  • My School is fun

  • NULL

  • fun

  • ./argv

  • My School

  • is

  • School

  • is fun

  • My

Question #6

In the following command, what is argv[2]?

$ ./argv "My School" "is fun"

  • My School is fun

  • NULL

  • fun

  • ./argv

  • My School

  • is

  • School

  • is fun

  • My

Tasks

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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-whatsmyname.c -o mynameis
julien@ubuntu:~/0x0A. argc, argv$ ./mynameis
./mynameis
julien@ubuntu:~/0x0A. argc, argv$ mv mynameis mynewnameis
julien@ubuntu:~/0x0A. argc, argv$ ./mynewnameis
./mynewnameis
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 0-whatsmyname.c

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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-args.c -o nargs
julien@ubuntu:~/0x0A. argc, argv$ ./nargs
0
julien@ubuntu:~/0x0A. argc, argv$ ./nargs hello
1
julien@ubuntu:~/0x0A. argc, argv$ ./nargs "hello, world"
1
julien@ubuntu:~/0x0A. argc, argv$ ./nargs hello, world
2
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 1-args.c

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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-args.c -o args
julien@ubuntu:~/0x0A. argc, argv$ ./args
./args
julien@ubuntu:~/0x0A. argc, argv$ ./args You can do anything, but not everything.
./args
You
can
do
anything,
but
not
everything.
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 2-args.c

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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-mul.c -o mul
julien@ubuntu:~/0x0A. argc, argv$ ./mul 2 3
6
julien@ubuntu:~/0x0A. argc, argv$ ./mul 2 -3
-6
julien@ubuntu:~/0x0A. argc, argv$ ./mul 2 0
0
julien@ubuntu:~/0x0A. argc, argv$ ./mul 245 3245342
795108790
julien@ubuntu:~/0x0A. argc, argv$ ./mul
Error
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 3-mul.c

4. To infinity and beyond

Write a program that adds positive numbers.

  • 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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 4-add.c -o add
julien@ubuntu:~/0x0A. argc, argv$ ./add 1 1
2
julien@ubuntu:~/0x0A. argc, argv$ ./add 1 10 100 1000
1111
julien@ubuntu:~/0x0A. argc, argv$ ./add 1 2 3 e 4 5
Error
julien@ubuntu:~/0x0A. argc, argv$ ./add
0
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 4-add.c

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
julien@ubuntu:~/0x0A. argc, argv$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 100-change.c -o change
julien@ubuntu:~/0x0A. argc, argv$ ./change
Error
julien@ubuntu:~/0x0A. argc, argv$ ./change 10
1
julien@ubuntu:~/0x0A. argc, argv$ ./change 100
4
julien@ubuntu:~/0x0A. argc, argv$ ./change 101
5
julien@ubuntu:~/0x0A. argc, argv$ ./change 13
3
julien@ubuntu:~/0x0A. argc, argv$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0A-argc_argv
  • File: 100-change.c