实现简易版shell

操作系统小组作业，实现一个简易shell，shell实现了下列命令

exit------退出终端命令

clr-------清屏命令

time-----时间命令

myshell----欢迎命令

quit-----终止命令

pwd-----路径命令

cat-----查看文件命令

help---帮助命令

help [参数]---查看某个具体的命令的注释

ls -l-----查看目录下的文件命令

只实现了简单的几个命令，仅做参考,代码如下

#include<bits/stdc++.h>
#include<unistd.h>
#include<stdio.h>
#include<sys/types.h>
#include<pwd.h>
#include<time.h>
#include<dirent.h>
#include<stdlib.h>
#include<sys/stat.h>
#include<fcntl.h>
#include <grp.h>
  #include <sys/wait.h>
#include<memory.h>
using namespace std;
#define MAX_LINE 80
#define MAX_NAME_LEN 50
#define MAX_PATH_LEN 1000
int cmd_cnt;
char *cmd_array[MAX_LINE/2+1];
string st;
void mytime(){
    int weekday;
    int month;
    time_t tvar;
    struct tm *tp;
    time(&tvar);
    tp=localtime(&tvar);//获取本地时间
    weekday=tp->tm_wday;
    switch(weekday){//根据不同的值打印不同的星期
    case 1:
        printf("Mon ");
        break;
    case 2:
        printf("Tues ");
        break;
    case 3:
        printf("Wed ");
        break;
    case 4:
        printf("Thur ");
        break;
    case 5:
        printf("Fri ");
        break;
    case 6:
        printf("Sat ");
        break;
    case 7:
        printf("Sun ");
        break;
    default:
        break;
    }
    month=1+tp->tm_mon;//必须要加1，经过查阅资料：tm_mon比实际的值少了1
    switch(month){//根据不同的值打印月份名
    case 1:
        printf("Jan ");
        break;
    case 2:
        printf("Feb ");
        break;
    case 3:
        printf("Mar ");
        break;
    case 4:
        printf("Apr ");
        break;
    case 5:
        printf("May ");
        break;
    case 6:
        printf("Jun ");
        break;
    case 7:
        printf("Jul ");
        break;
    case 8:
        printf("Aug ");
        break;
    case 9:
        printf("Sep ");
        break;
    case 10:
        printf("Oct ");
        break;
    case 11:
        printf("Nov ");
        break;
    case 12:
        printf("Dec ");
        break;
    default:
        break;
    }
    printf("%d ",tp->tm_mday);//日期
    printf("%d:",tp->tm_hour);//小时
    printf("%d:",tp->tm_min);//分钟
    printf("%d ",tp->tm_sec);//秒
    printf("CST ");//CST，意思是China Standard Time
    printf("%d
",1900+tp->tm_year);//必须加上1900，返回的值并不是完整的年份，比真实值少了1900
}
void welcome(){
    //如下是欢迎信息
    //为了是程序更友好，加入了颜色
    //颜色是紫色，背景色与shell相同
    printf("e[32mwelcome to myshelle[0m
");
    printf("e[32mit's a Lunix-like shell program made by use[0m
");
    printf("e[32mhope you have a good time with it :-)e[0m
");
}
void mypwd(){
    char pathname[MAX_PATH_LEN];
    if(getcwd(pathname,MAX_PATH_LEN)){//获取路径名
        printf("%s
",pathname);
    }
    else{//如果出错
        perror("myshell: getcwd");//报错
        exit(1);
    }
}

void myquit(){
    printf("Thanks for your using，bye-bye！
");
    sleep(1);//暂停1s，看上去视觉效果好一些
    exit(0);
}
void exit(){
   exit(0);
}
void myclr(){
    cout << "33[2J";
    cout << "33[H";

}

void printprompt(){//实现命令提示符

    char hostname[MAX_NAME_LEN];
    char pathname[MAX_PATH_LEN];
    struct passwd *pwd;
    pwd=getpwuid(getuid());
    gethostname(hostname,MAX_NAME_LEN);
    printf("e[34m%s@%s:e[0m",pwd->pw_name,hostname);

        printf("$");


}


//*****************************************************获得文件权限属性
void getPower(mode_t mod)
{
  for(int n=8; n>=0; n--)
  {
      if(mod&(1<<n))//移位运算,1左移位n位
      {
          switch(n%3)
          {
          case 2:
              printf("r");
              break;
          case 1:
              printf("w");
              break;
          case 0:
              printf("x");
              break;
          default:
              break;
          }
      }
      else
      {
          printf("-");
      }
        }
}



void cat(string filename){
  ifstream fin( filename);
  char  str[200];
  while ( fin.getline(str,200) )
  {
    cout  << str << endl;
  }
}




void ls(string allstr,string substr){

/******************************ls*************************
*
*dirName[]   :store single filename
*dir         :point to currnt directory
*rent        :指针变量
*st          :文件基本操作
**********************************************************/


struct stat st;
char dirName[100];

DIR *dir;
struct dirent *rent;//struct
dir = opendir(".");


  if(allstr== "ls"){

    if(dir != NULL)
    {
      while((rent=readdir(dir)))
      {

        strcpy(dirName,rent->d_name);
        if (dirName[0]!='.' && dirName)
        {
          cout << dirName<<'	';
        }
      }
    }

    cout << endl;
  }
  else if(dir == NULL)
  {
      cout << "*****empty*****"<<endl;
  }
  else if(allstr != "ls -l")
  {
    cout << substr+":  "+ "unrecognized option "+"'"+allstr.substr(substr.length())+"'"<<endl;
    cout << "Try 'ls -l' "<<endl;
  }

  /******************************************ls -l*************************/

  else if(allstr == "ls -l")
  {
    while( rent = readdir(dir) )
    {
      strcpy(dirName,rent->d_name);
      if (dirName[0]!='.' && dirName)
      {
        if(-1 != stat(rent->d_name, &st) )//get fileInfomation from filename p->d_name and save it in structure stat
        {
          getPower(st.st_mode);        //get r-w-d
          cout <<" "<<st.st_nlink<<" ";//get number of file links
          cout <<" "<<getpwuid(st.st_uid)->pw_name<<" ";//owner name
          cout <<getgrgid(st.st_gid)->gr_name<<'	'; //group name
          cout << st.st_size<<'	';  //get total size , in bytes

          //printf 12 char and align = left
          printf("%.12s  ",4+ctime(&st.st_mtime));   //the last time of changing file
          cout << dirName;
          cout << endl;
        }
      }
    }
  }

  closedir(dir);
}




//****************************************************获得输入字符
string strInput()
{
  string str;
  string res;
  char c;
  while( (c = getchar()) != '
')
    str += c;

  vector<string> arr;
  istringstream istr(str);
  string word;
  while(istr>>word) {
      arr.push_back(word);//添加元素到尾部
  }

  for(int i=0; i<arr.size(); i++) {
    if(i != arr.size() - 1)
        res += arr[i]+" ";
    else
      res += arr[i];
  }

  return res;
}
///////////////////////////////////////////////////////////help命令
void print_manual(){
    printf("welcome to the manual of myshell, hope it's useful for you
");
    printf("the following are the BUILT-IN commands supported by myshell
");
    printf("
");

    printf("exit:      exit                            quit the shell directly
");
    printf("clr:       clr                             clear the screen
");
    printf("time:      time                            show the current time in an elegant format
");
    printf("myshell:   myshell [filename]              execute a batchfile
");
    printf("quit:      quit                            quit the shell with thank-you
");
    printf("pwd:       pwd                             print the current working directory
");
    printf("help:      help/help [command]             show the manual of help/get help info of a sepcified command
");

}
void print_cmdinfo(string cmdname){

     if(cmdname=="exit"){
        printf("usage:quit the shell directly
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else if(cmdname=="pwd"){
        printf("usage:print the current working directory
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else if(cmdname=="time"){
        printf("usage:show the current time in an elegant format
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else if(cmdname=="clr"){
        printf("usage:clear screen
");
        printf("options            descriptions
");
        printf("none               see the manual,pls
");
    }
    else if(cmdname=="myshell"){
        printf("usage:execute a batchfile
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else if(cmdname=="help"){
        printf("usage:show the manual of help/get help info of a sepcified command
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else if(cmdname=="quit"){
        printf("usage:quit the shell with thank-you information
");
        printf("options            descriptions
");
        printf("none               see the manual,plz
");
    }
    else {//如果有错
        printf("myshell: help: Invalid use of help command
");//打印提示信息
    }

}
void myhelp(){
    if(cmd_cnt==1){//如果是不带参数的help
        print_manual();//调用子函数print_manual打印用户帮助手册
    }
    else if(cmd_cnt==2){//如果格式是"help [command]"
        print_cmdinfo(st);//打印单个命令的帮助信息
    }

}
void help(string str){
 if(str=="help"){
     cmd_cnt=1;
     }
     else if(str.length()>5){

      cmd_cnt=2;
      st=str.substr(5,str.length());
     }

     myhelp();
}
/////////////////////////////////////////////////////////////////////////////////
int main()
{
  string n;
  string str1; //first str !=include space
  string str2;


  while(true){
      printprompt();
      n=strInput();

    istringstream istr(n);
    istr >> str1>>str2;

    if(str1 == "ls"){
        ls(n,str1);
        continue;
    }
      if(n=="exit")//退出
          exit();
       else if(n=="clr"){
          myclr();
       }
       else if(n=="time")
       {
           mytime();
       }
       else if(n=="myshell")
       {
           welcome();
       }
       else if(n=="quit")
       {
       myquit();
       }
       else if(n=="pwd")
       {
       mypwd();
       }
    else if(str1 == "cat"){
      cat(str2);
    }
       else if(str1=="help"){
       help(n);
       }
    else
        cout << "invaild command" << endl;

  }

  return 0;
}

如果需要的话，下面链接里面有我对该代码的部分不常见的函数和结构体的注释，如需要的可以看一下

https://files-cdn.cnblogs.com/files/henuliulei/shellzhushi.zip