a minishell in C created for lab1 of my operating system course.

minishell.c

#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <string.h>
#include <stdlib.h>

#define prompt "\e[32mminishell\e[0m> "

void builtin_exit(char *argv[16]) {
    exit(0);
}

void builtin_help(char *argv[16]) {
    printf("====== minishell by miigon from SZU ======\n");
    printf("type the name of a program to run.\n");
    printf("use `help` to show the help message\n");
    printf("use `exit` to exit the current shell\n");
}

typedef void(*builtin_func)(char*[16]);
const char *builtin_commands[] = {
    "exit",
    "help",
    NULL
};
builtin_func builtin_funcs[] = {
    builtin_exit,
    builtin_help,
};

int getBuiltin(const char *prog) {
    for(int i=0;builtin_commands[i] != NULL;i++) {
        if(strcmp(prog, builtin_commands[i]) == 0) {
            return i;
        }
    }
    return -1;
}

int main() {
    printf("minishell by Miigon from SZU (2021-03-21)\n");
    while(1) {
        printf(prompt);

        char *line;
        size_t size;
        getline(&line, &size, stdin);
        char args[16][4096];
        char *argv[16];
        char *p = line;

        // process arguments
        char argc = 1;
        char i = 0;
        while(*p!='\n' && *p!='\0') {
            if(*p == ' ') {
                args[argc-1][i++] = '\0';
                argv[argc-1] = args[argc-1];
                argc++;
                i = 0;
            } else {
                args[argc-1][i++] = *p;
            }
            p++;
        }
        argv[argc-1] = args[argc-1];
        args[argc-1][i++] = '\0';
        argv[argc] = NULL;

        int builtin_index;
        if((builtin_index=getBuiltin(argv[0])) != -1) { // builtin functions
            builtin_funcs[builtin_index](argv);
        } else {
            // execute
            int pid = fork(); // fork the shell
            if(pid == -1){
                printf("failed creating child process\n");
            } else if(pid == 0) { // child
                // replace the child shell process image with the program
                // to run, executing the program.
                if(execvp(argv[0], argv) == -1) {
                    perror("execution failed");
                    exit(1);
                };
            } else { // parent (shell)
                waitpid(pid, NULL, 0);
            }
        }

    }
    return 0;
}