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 = ;

     fgets(cmd, CMDSIZE, stdin);

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

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

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

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

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

     while () {
         prompt();

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

     return ;
 }