C语言接口的写法（以toyls命令为例）

#include <unistd.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define CMDSIZE 4096

static void prompt(void)
{
    printf("[mysh]$ ");
    fflush(stdout);
}

static void getcmd(char *cmd, char **argv)
{
    int i = 0;

    fgets(cmd, CMDSIZE, stdin);

    argv[i] = strtok(cmd, " 	
");
    for (i++; argv[i - 1] != NULL; i++) {
        argv[i] = strtok(NULL, " 	
");
    }
}

static void myexit(char **argv)
{
    exit(0);
}

static void mycd(char **argv)
{
    chdir(argv[1]);
}

#define NAMESIZE 256
struct {
    void (*func)(char **);
    char name[NAMESIZE];
} internal_list[] = {
    {myexit, "exit"},
    {mycd, "cd"},
    {NULL, },
};

static int internal_ind(const char *name)
{
    int i;

    for (i = 0; internal_list[i].func != NULL; i++) {
        if (strcmp(name, internal_list[i].name) == 0) {
            return i;
        }
    }
    return -1;
}

int main(void)
{
    char cmd[CMDSIZE];
    char *argv[CMDSIZE / 2];
    pid_t pid;
    int ind;

    while (1) {
        prompt();

        getcmd(cmd, argv);
        if ((ind = internal_ind(argv[0])) != -1) {
            internal_list[ind].func(argv);
        } else {
            pid = fork();
            /* if error */
            if (pid == 0) {
                execvp(argv[0], argv);
                perror(argv[0]);
                exit(1);
            }
            wait(NULL);
        }
    }

    return 0;
}