pointers_arrays_strings

C - Pointers, arrays and strings 💀

Description 😶‍🌫️

This project is about what and how to use pointers and arrays and the differences between the two as well as how to use and manipulate strings in C.

Tests ✔️

• tests: Folder of test files. Provided by Holberton School.

Helper File 🙌

• _putchar.c: C function that writes a character to stdout.

Header File 📁

• main.h: Header file containing prototypes for all functions written in the project.

File	Prototype
0-reset_to_98.c	void reset_to_98(int *n);
1-swap.c	void swap_int(int *a, int *b);
2-strlen.c	int _strlen(char *s);
3-puts.c	void _puts(char *str);
4-print_rev.c	void print_rev(char *s);
5-rev_string.c	void rev_string(char *s);
6-puts2.c	void puts2(char *str);
7-puts_half.c	void puts_half(char *str);
8-print_array.c	void print_array(int *a, int n);
9-strcpy.c	char *_strcpy(char *dest, char *src);
100-atoi.c	int _atoi(char *s);
0-strcat.c	char *_strcat(char *dest, char *src);
1-strncat.c	char *_strncat(char *dest, char *src, int n);
2-strncpy.c	char *_strncpy(char *dest, char *src, int n);
3-strcmp.c	int _strcmp(char *s1, char *s2);
4-rev_array.c	void reverse_array(int *a, int n);
5-string_toupper.c	char *string_toupper(char *);
6-cap_string.c	char *cap_string(char *);
7-leet.c	char *leet(char *);
0-memset.c	char *_memset(char *s, char b, unsigned int n);
1-memcpy.c	char *_memcpy(char *dest, char *src, unsigned int n);
2-strchr.c	char *_strchr(char *s, char c);
3-strspn.c	unsigned int _strspn(char *s, char *accept);
4-strpbrk.c	char *_strpbrk(char *s, char *accept);
5-strstr.c	char *_strstr(char *haystack, char *needle);
7-print_chessboard.c	void print_chessboard(char (*a)[8]);

Formatting and Examples 🤓

Compile's flags

-Wall -pedantic -Werror -Wextra -std=gnu89

Example

julien@ubuntu:~/$ 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:~/$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 7-main.c 7-puts_half.c -o 7-puts_half
julien@ubuntu:~/$ ./7-puts_half 
56789
julien@ubuntu:~/$ 

Tasks 📃

• 0. 98 Battery st.

  • 0-reset_to_98.c: C function that takes a pointer to an int as a parameter and updates the value it points to to 98.

• 1. Don't swap horses in crossing a stream

  • 1-swap.c: C function that swaps the value of two integers.

• 2. This report, by its very length, defends itself against the risk of being read

  • 2-strlen.c: C function that returns the length of a string.

• 3. I do not fear computers. I fear the lack of them

  • 3-puts.c: C function that prints a string, followed by a new line, to stdout.

• 4. I can only go one way. I've not got a reverse gear

  • 4-print_rev.c: C function that prints a string, in reverse, followed by a new line.

• 5. A good engineer thinks in reverse and asks himself about the stylistic consequences of the components and systems he proposes

  • 5-rev_string.c: C function that reverses a string.

• 6. Half the lies they tell about me aren't true

  • 6-puts2.c: C function that prints every other character of a string, followed by a new line.

• 7. Winning is only half of it. Having fun is the other half

  • 7-puts_half.c: C function that prints the second half of a string, followed by a new line.

• 8. Arrays are not pointers

  • 8-print_array.c: C function that prints an input n elements of an array of integers, followed by a new line.
    • Numbers are separated by a comma followed by a space.
    • Numbers are displayed in the same order as they are stored in the array.

• 9. strcpy

  • 9-strcpy.c: C function that copies the string pointed to by src, including the terminating null byte (\0), to the buffer pointed to by dest.
    • Returns the pointer to dest.

• 10. Great leaders are willing to sacrifice the numbers to save the people. Poor leaders sacrifice the people to save the numbers

  • 100-atoi.c: C function that converts a string to an integer without using long, new variable arrays, or hard-coded special values, as follows:
    • The number in the string can be preceded by an infinite number of characters.
    • Takes into account all + and - signs before the number.
    • If there are no numbers in the string, the function returns 0.

• 0. strcat

  • 0-strcat.c: C function that concatenates two strings.
    • Adds a terminating null byte at end.

• 1. strncat

  • 1-strncat.c: C function that concatenates two strings using at most an inputted number of bytes.
    • Adds a terminating null byte at end, unless source string is longer than maximum byte number.

• 2. strncpy

  • 2-strncpy.c: C function that copies a string, including the terminating null byte, using at most an inputted number of bytes.
    • If the length of the source string is less than the maximum byte number, the remainder of the destination string is filled with null bytes.
    • Works identically to the standard library function strncpy.

• 3. strcmp

  • 3-strcmp.c: C function that compares two strings.
    • Returns the difference in bytes at point of difference.
    • Works identically to the standard library function strcmp.

• 4. I am a kind of paranoid in reverse. I suspect people of plotting to make me happy

  • 4-rev_array.c: C function that reverses the content of an array of integers.

• 5. Always look up

  • 5-string_toupper.c: C function that changes all lowercase letters of a string to uppercase.

• 6. Expect the best. Prepare for the worst. Capitalize on what comes

  • 6-cap_string.c: C function that capitalizes all words of a string.

• 7. Mozart composed his music not for the elite, but for everybody

  • 7-leet.c: C function that encodes a string into 1337, without switch or ternary operations and using only one if and two loops.
    • Letters a and A are replaced by 4.
    • Leters e and E are replaced by 3.
    • Letters o and O are replaced by 0.
    • Letters t and T are replaced by 7.
    • Letters l and L are replaced by 1.

• 0. memset

  • 0-memset.c: C function that fills the first n bytes of memory area pointed to by s with the constant byte b.
    • Returns a pointer to the filled memory area s.

• 1. memcpy

  • 1-memcpy.c: C function that copies n bytes from memory area src to memory area dest.
    • Returns a pointer to the memory area dest.

• 2. strchr

  • 2-strchr.c: C function that returns a pointer to the first occurence of the character c in the string s.
    • If the character is not found, the function returns NULL.

• 3. strspn

  • 3-strspn.c: C function that returns the number of bytes in the intitial segment of memory area s which consist only of bytes from a substring accept.

• 4. strpbrk

  • 4-strpbrk.c: C function that locates the first occurence in a string s of any of the bytes in a string accept.
    • Returns a pointer to the byte in s that matches one of the bytes in accept.
    • If no matching byte is found, the function returns NULL.

• 5. strstr

  • 5-strstr.c: C function that finds the first occurence of a substring needle in a string haystack.
    • The terminating null bytes (\0) are not compared.
    • Returns a pointer to the beginning of the located substring.
    • If the substring is not found, the function returns NULL.

• 6. Chess is mental torture

  • 7-print_chessboard.c: C function that prints the chessboard.