0x05-pointers_arrays_strings

0x05. C - Pointers, arrays and strings C By: Julien Barbier Weight: 1 Ongoing second chance project - started Feb 27, 2023 6:00 AM, must end by Mar 1, 2023 6:00 AM An auto review will be launched at the deadline In a nutshell… Auto QA review: 0.0/71 mandatory & 0.0/24 optional Altogether: 0.0% Mandatory: 0.0% Optional: 0.0% Calculation: 0.0% + (0.0% * 0.0%) == 0.0% Concepts For this project, we expect you to look at these concepts:

Pointers and arrays Data Structures

Resources Read or watch:

C - Arrays C - Pointers C - Strings Memory Layout Learning Objectives At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General What are pointers and how to use them What are arrays and how to use them What are the differences between pointers and arrays How to use strings and how to manipulate them Scope of variables Copyright - Plagiarism You are tasked to come up with solutions for the tasks below yourself to meet with the above learning objectives. You will not be able to meet the objectives of this or any following project by copying and pasting someone else’s work. You are not allowed to publish any content of this project. Any form of plagiarism is strictly forbidden and will result in removal from the program. 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 You are not allowed to use the standard library. Any use of functions like printf, puts, etc… is forbidden You are allowed to use _putchar You don’t have to push _putchar.c, we will use our file. If you do it won’t be taken into account In the following examples, the main.c files are shown as examples. You can use them to test your functions, but you don’t have to push them to your repo (if you do we won’t take them into account). We will use our own main.c files at compilation. Our main.c files might be different from the one shown in the examples 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 More Info You do not need to learn about pointers to functions, pointers to pointers, multidimensional arrays, arrays of structures, malloc and free - yet.

Quiz questions Great! You've completed the quiz successfully! Keep going! (Show quiz) Tasks 0. 98 Battery st. mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that takes a pointer to an int as parameter and updates the value it points to to 98.

Prototype: void reset_to_98(int *n); julien@ubuntu:~/0x05$ cat 0-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { int n;

  n = 402; printf("n=%d\n", n); reset_to_98(&n); printf("n=%d\n", n); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-main.c 0-reset_to_98.c -o 0-98 julien@ubuntu:/0x05$ ./0-98 n=402 n=98 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 0-reset_to_98.c

1. Don't swap horses in crossing a stream mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that swaps the values of two integers.

Prototype: void swap_int(int *a, int *b); julien@ubuntu:~/0x05$ cat 1-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { int a; int b;

  a = 98; b = 42; printf("a=%d, b=%d\n", a, b); swap_int(&a, &b); printf("a=%d, b=%d\n", a, b); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-main.c 1-swap.c -o 1-swap julien@ubuntu:/0x05$ ./1-swap a=98, b=42 a=42, b=98 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 1-swap.c

2. This report, by its very length, defends itself against the risk of being read mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that returns the length of a string.

Prototype: int _strlen(char *s); FYI: The standard library provides a similar function: strlen. Run man strlen to learn more.

julien@ubuntu:~/0x05$ cat 2-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { char *str; int len;

  str = "My first strlen!"; len = _strlen(str); printf("%d\n", len); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-main.c 2-strlen.c -o 2-strlen julien@ubuntu:/0x05$ ./2-strlen 16 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 2-strlen.c

3. I do not fear computers. I fear the lack of them mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that prints a string, followed by a new line, to stdout.

Prototype: void _puts(char *str); FYI: The standard library provides a similar function: puts. Run man puts to learn more.

julien@ubuntu:~/0x05$ cat 3-main.c #include "main.h"

/**

• main - check the code

• Return: Always 0. */ int main(void) { char *str;

  str = "I do not fear computers. I fear the lack of them - Isaac Asimov"; _puts(str); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 3-main.c 3-puts.c -o 3-puts julien@ubuntu:/0x05$ ./3-puts I do not fear computers. I fear the lack of them - Isaac Asimov julien@ubuntu:~/0x05$

Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 3-puts.c

4. I can only go one way. I've not got a reverse gear mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that prints a string, in reverse, followed by a new line.

Prototype: void print_rev(char *s); julien@ubuntu:~/0x05$ cat 4-main.c #include "main.h"

/**

• main - check the code

• Return: Always 0. */ int main(void) { char *str;

  str = "I do not fear computers. I fear the lack of them - Isaac Asimov"; print_rev(str); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 4-main.c 4-print_rev.c -o 4-print_rev julien@ubuntu:/0x05$ ./4-print_rev vomisA caasI - meht fo kcal eht raef I .sretupmoc raef ton od I julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 4-print_rev.c

5. A good engineer thinks in reverse and asks himself about the stylistic consequences of the components and systems he proposes mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that reverses a string.

Prototype: void rev_string(char *s); julien@ubuntu:~/0x05$ cat 5-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { char s[10] = "My School";

  printf("%s\n", s); rev_string(s); printf("%s\n", s); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 5-main.c 5-rev_string.c -o 5-rev_string julien@ubuntu:/0x05$ ./5-rev_string My School loohcS yM julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 5-rev_string.c

6. Half the lies they tell about me aren't true mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that prints every other character of a string, starting with the first character, followed by a new line.

Prototype: void puts2(char *str); julien@ubuntu:~/0x05$ cat 6-main.c #include "main.h"

/**

• main - check the code

• Return: Always 0. */ int main(void) { char *str;

  str = "0123456789"; puts2(str); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 6-main.c 6-puts2.c -o 6-puts2 julien@ubuntu:/0x05$ ./6-puts2 02468 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 6-puts2.c

7. Winning is only half of it. Having fun is the other half mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that prints half of a string, followed by a new line.

Prototype: void puts_half(char *str); The function should print the second half of the string If the number of characters is odd, the function should print the last n characters of the string, where n = (length_of_the_string - 1) / 2 julien@ubuntu:~/0x05$ cat 7-main.c #include "main.h"

/**

• main - check the code

• Return: Always 0. */ int main(void) { char *str;

  str = "0123456789"; puts_half(str); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 7-main.c 7-puts_half.c -o 7-puts_half julien@ubuntu:/0x05$ ./7-puts_half 56789 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 7-puts_half.c

8. Arrays are not pointers mandatory Score: 0.0% (Checks completed: 0.0%) Write a function that prints n elements of an array of integers, followed by a new line.

Prototype: void print_array(int *a, int n); where n is the number of elements of the array to be printed Numbers must be separated by comma, followed by a space The numbers should be displayed in the same order as they are stored in the array You are allowed to use printf julien@ubuntu:~/0x05$ cat 8-main.c #include "main.h"

/**

• main - check the code for

• Return: Always 0. */ int main(void) { int array[5];

  array[0] = 98; array[1] = 402; array[2] = -198; array[3] = 298; array[4] = -1024; print_array(array, 5); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 8-main.c 8-print_array.c -o 8-print_array julien@ubuntu:/0x05$ ./8-print_array 98, 402, -198, 298, -1024 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 8-print_array.c

9. strcpy mandatory Score: 0.0% (Checks completed: 0.0%) Prototype: char *_strcpy(char *dest, char *src); Write a function that copies the string pointed to by src, including the terminating null byte (\0), to the buffer pointed to by dest.

Return value: the pointer to dest FYI: The standard library provides a similar function: strcpy. Run man strcpy to learn more.

julien@ubuntu:~/0x05$ cat 9-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { char s1[98]; char *ptr;

  ptr = _strcpy(s1, "First, solve the problem. Then, write the code\n"); printf("%s", s1); printf("%s", ptr); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 9-main.c 9-strcpy.c -o 9-strcpy julien@ubuntu:/0x05$ ./9-strcpy First, solve the problem. Then, write the code First, solve the problem. Then, write the code julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 9-strcpy.c

10. Great leaders are willing to sacrifice the numbers to save the people. Poor leaders sacrifice the people to save the numbers #advanced Score: 0.0% (Checks completed: 0.0%) Write a function that convert a string to an integer.

Prototype: int _atoi(char *s); The number in the string can be preceded by an infinite number of characters You need to take into account all the - and + signs before the number If there are no numbers in the string, the function must return 0 You are not allowed to use long You are not allowed to declare new variables of “type” array You are not allowed to hard-code special values We will use the -fsanitize=signed-integer-overflow gcc flag to compile your code. FYI: The standard library provides a similar function: atoi. Run man atoi to learn more.

julien@ubuntu:~/0x05$ cat 100-main.c #include "main.h" #include <stdio.h>

/**

• main - check the code

• Return: Always 0. */ int main(void) { int nb;

  nb = _atoi("98"); printf("%d\n", nb); nb = _atoi("-402"); printf("%d\n", nb); nb = _atoi(" ------++++++-----+++++--98"); printf("%d\n", nb); nb = _atoi("214748364"); printf("%d\n", nb); nb = _atoi("0"); printf("%d\n", nb); nb = _atoi("Suite 402"); printf("%d\n", nb); nb = _atoi(" + + - -98 Battery Street; San Francisco, CA 94111 - USA "); printf("%d\n", nb); nb = _atoi("---++++ -++ Sui - te - 402 #cisfun :)"); printf("%d\n", nb); return (0); } julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 -fsanitize=signed-integer-overflow 100-main.c 100-atoi.c -o 100-atoi julien@ubuntu:/0x05$ ./100-atoi 98 -402 -98 214748364 0 402 98 402 julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 100-atoi.c

11. Don't hate the hacker, hate the code #advanced Score: 0.0% (Checks completed: 0.0%) Create a program that generates random valid passwords for the program 101-crackme.

You are allowed to use the standard library You don’t have to pass the betty-style tests (you still need to pass the betty-doc tests) man srand, rand, time gdb and objdump can help julien@ubuntu:/0x05$ gcc -Wall -pedantic -Werror -Wextra 101-keygen.c -o 101-keygen julien@ubuntu:/0x05$ ./101-crackme "./101-keygen" Tada! Congrats julien@ubuntu:~/0x05$ Repo:

GitHub repository: alx-low_level_programming Directory: 0x05-pointers_arrays_strings File: 101-keygen.c