简单shell实现

#include <stdio.h>
#include <unistd.h>
#include <wait.h>
#define MAXLINE 80

void setup (char inputBuffer[], char *argv[])
{

    int i, j;
    char *p;
    i = 0;
    for (p = inputBuffer; ;p++)/*将字符命令一段一段拆分开来,如输入ls -l,则argv[0]= "ls",argv[1]="-l",argv[2]=NULL*/
    {
        argv[i++] = p;
        while (*p != ‘ ‘ && *p != ‘\0‘)
            p++;
        if (*p == ‘\0‘)
        {
            break;
        }
        *p = ‘\0‘;
       }
    argv[i] = NULL;/*最后一个参数须用空指针NULL作结束*/
    execvp (argv[0], argv);/*执行命令,argv[0]放着执行的命令，其余的argv放着参数*/
}



int main()
{

    char inputBuffer[MAXLINE];
    char *argv[MAXLINE / 2 - 1];

    while (1)
    {
        printf ("COMMAND->");
          gets (inputBuffer);/*输入命令*/
        setup (inputBuffer, argv);
                printf ("扑街！");
    }
    return 0;
}

#include <stdio.h>
#include <unistd.h>
//#define SIZE 20
#define MAXLINE 80
char *p;

void setup (char inputBuffer[], char *argv[])
{
    int i, j;
    i = 0;
    for (p = inputBuffer; ;p++)/*一个一个地将输入字符分开*/
    {
        argv[i++] = p;
        while (*p != ‘ ‘ && *p != ‘\0‘)
            p++;
        if (*p == ‘\0‘)
        {
            break;
        }
        *p = ‘\0‘;
       }
    argv[i] = NULL;
    pid_t pid
    pid = fork();/*新建一个子进程*/
    if (pid == 0)/*对于子进程，执行输入的命令*/
    {
     execvp (argv[0], argv);
     printf ("command not found\n");/*如果execvp执行失败的话，会返回-1,也就是这句话会被执行*/
    }

    else if( pid > 0 )/*对于父进程，等待*/
    {
     wait(NULL);/*父进程等待子进程执行完*/
    }

     else /*否则的话，就出错了*/
     {
      printf ("fork error\n");
     }
}

int main()
{
    char inputBuffer[MAXLINE];
    char *argv[MAXLINE / 2 - 1];

    while (1)
    {
        printf ("COMMAND->");
          gets (inputBuffer);
        /*关于scanf和gets,scanf对于输入的字符遇到空格或回车就结束了，而gets对于输入的空格也接受*/
        setup (inputBuffer, argv);

    }
    return 0;
}