Include an external library in C

Question

I\'m attempting to use a C library for an opencourseware course from Harvard. The instructor\'s instructions for setting up the external lib can be found here.

I

Answer 1

I take this course and sometimes I need to practice offline while I am traveling or commuting. Under Windows using MinGW and Notepad++ as an IDE (because I love it and use it usually while codding python) I finally found a solution and some time to write it down.

Starting from scratch. Steps for setting up gcc C compiler, if already set please skip to 5

1. Download Git and install. It includes Git Bash, which is MINGW64 linux terminal. I prefer to use Git as I need linux tools such as sed, awk, pull, push on my Windows and can replace Guthub's terminal.
2. Once Git installed make sure that gcc packages are installed. You can use my configuration for reference...

3. Make sure your compiler works. Throw it this simple code,

   • by saving it in your working directory Documents/Harvard_CS50/Week2/ hello.c

   #include 
   
   int main(void)
   {
    printf("Hello StackOverflow\n");
   }
   

   • start Git Bash -> navigate to working directory

   cd Documents/Harvard_CS50/Week2/

   • compile it in bash terminal

   gcc helloworld.c -o helloworld.exe

   • execute it using bash terminal

   ./helloworld.exe

   Hello StackOverflow

   4. If you see Hello StackOverflow, your compiler works and you can write C code.

Now to the important bit, installing CS50 library locally and using it offline. This should be applicable for any other libraries introduced later in the course.

5. Download latest source code file cs50.c and header file cs50.h from https://github.com/cs50/libcs50/tree/develop/src and save them in Documents/Harvard_CS50/src

6. Navigate into src directory and list the files to make sure you are on the right location using

   ls

   cs50.c cs50.h

7. Cool, we are here. Now we need to compile object file for the library using

   gcc -c -ggdb -std=c99 cs50.c -o cs50.o

8. Now using the generated cs50.o object file we can create our cs50 library archive file.

   ar rcs libcs50.a cs50.o

9. After all this steps we ended with 2 additional files to our original files. We are interested in only 2 of them cs50.h libcs50.a

   ls

   cs50.c cs50.h cs50.o libcs50.a

10. Copy Library and header files to their target locations. My MinGW is installed in C:\ so I copy them there

    cs50.h --> C:\MinGW\include

    libcs50.a --> C:\MinGW\lib

Testing the cs50 Library

To make sure our library works, we can throw one of the example scripts in the lecture and see if we can compile it using cs50.h header file for the get_string() method.

#include 
#include 

int main(void) 
{
    printf("Please input a string to count how long it is: ");
    string s = get_string();
    int n = 0;
    while (s[n] != '\0')
        {
            n++;
        }
    printf("Your string is %i chars long\n", n); 
}

11. Compile cs50 code using gcc and cs50 library. I want to be explicit and use:

    gcc -ggdb -std=c99 -Wall -Werror test.c -lcs50 -o test.exe

    But you can simply point the source, output filename and cs50 library

    gcc test.c -o test.exe -lcs50

Here we go, program is compiled using header and methods can be used within.

If you want Notepad++ as an IDE you can follow this tip to set it up with gcc as a compiler and run your code from there. Just make sure your nppexec script includes the cs50 library

npp_save
gcc -ggdb -std=c99 -Wall -Werror "$(FULL_CURRENT_PATH)" -lcs50 -o "$(CURRENT_DIRECTORY)\$(NAME_PART).exe"
cmd /c "$(CURRENT_DIRECTORY)\$(NAME_PART).exe"