0x09-static_libraries

0x09-static_libraries Project

General What is a static library, how does it work, how to create one, and how to use it

Basic usage of ar, ranlib, nm

NOTE All the files within this Folder are made executable

This project finds solutions to the following:

Resource

• What Is A “C” Library? What Is It Good For?.
• Creating A Static “C” Library Using “ar” and “ranlib”.
• Using A "C" Library In A Program.
• What is difference between Dynamic and Static library(Static and Dynamic linking) (stop at 4:44)

Tasks

0. A library is not a luxury but one of the necessities of life : Creating a static library containing all the functions listed below.
   • Functions;

      int _putchar(char c);
      int _islower(int c);
      int _isalpha(int c);
      int _abs(int n);
      int _isupper(int c);
      int _isdigit(int c);
      int _strlen(char *s);
      void _puts(char *s);
      char *_strcpy(char *dest, char *src);
      int _atoi(char *s);
      char *_strcat(char *dest, char *src);
      char *_strncat(char *dest, char *src, int n);
      char *_strncpy(char *dest, char *src, int n);
      int _strcmp(char *s1, char *s2);
      char *_memset(char *s, char b, unsigned int n);
      char *_memcpy(char *dest, char *src, unsigned int n);
      char *_strchr(char *s, char c);
      unsigned int _strspn(char *s, char *accept);
      char *_strpbrk(char *s, char *accept);
      char *_strstr(char *haystack, char *needle);

   • File main.h contains all of the above functions created from previous projects.
   • Steps to create static library.
     • First compile all .c files to get our object files .o files. gcc -c *c
     • Then we create our static library from our object files. ar rc libmain.a *.o
     • Then we confirm if our static library was created successfully. ar -t libmain.a
     • We confirm if our object files were linked successfully. nm libmain.h
   • Compile the main code to test our static library this way: gcc -std=gnu89 main.c -L. -lmain -o quote
1. Without libraries what have we? We have no past and no future : Create a script that creates a library called liball.a from all the .c files that are in the current directory.

Alternatively you can create your static library this way

• gcc -c *.c > This converts .c files to .o (object) files

• ar rcs libmy.a *.o

• ar rc libmy.a *.o > This creates the static library "Libmy.a"

• ar -t libmy.a > This lists all files in libmy.a

• ranlib libmy.a > This converts to random library

  • After creating a static library and you would want to compile for testing use:

  • gcc -std=gnu89 main.c -L -lmy -o(new_file_name)