#include <stdio.h>    
#include <string.h>    
#include <stdlib.h>    
#include <errno.h>    
#include <fcntl.h>    
#include <unistd.h>    
#include <sys/types.h>    
#include <sys/stat.h>    
#include <sys/wait.h>  
  
#define SHELL_BUILDIN_CD 1    
#define SHELL_NORMAL 2    
  
  
#define BUFFSIZE 256  
  
/** 
using quit cmd to exit 
*/  
int isQuitCmd(char * arg){  
    static char *quit = "quit\n";  
    return strcmp(arg,quit) == 0 ? 1 : 0;  
  
}  
  
/** 
decide whether the cmd is build-in or normal 
*/  
int getCmdType(char *firstCmd){  
   if(strcmp(firstCmd ,"cd" ) == 0){  
     return SHELL_BUILDIN_CD;  
   }else{  
     return SHELL_NORMAL;  
   }  
  
  
}  

int parserCMD(char * cmdArray[], char *argv){  
    int cnt = 0;  
	int len = strlen(argv);
	argv[len-1]='\0';
    char *p = strtok (argv, " ");  
    while(p != NULL)  
    {   
		      cmdArray[cnt] = new char[25];
              strcpy(cmdArray[cnt],p);  
              cnt++;  
              if(p!=NULL)  
              p = (char *)strtok(p+strlen(p)+1," ");  
    } 
    return cnt;  
}  
  
  
 
int buildInCDCMD(char * args[]){  
   char curDir[BUFFSIZE]; 
   if( args[1] == NULL){
      char *cur = getenv("HOME");
	  printf("current Dir:%s\n",cur);
	  return 0;
   }
   char first = args[1][0];  
   if(first != '/' && first != '.'){  
      //concat the cd args with current dir  
      getcwd(curDir, BUFFSIZE);  
      strncat(curDir,"/",BUFFSIZE - strlen(curDir));  
   }  
   strncat(curDir,args[1],BUFFSIZE - strlen(curDir));  
     
   if(chdir(curDir) == -1){  
     fprintf(stderr,"chdir fail.......\n");  
   }  
   memset(curDir,0,sizeof(curDir));
   getcwd(curDir,BUFFSIZE);
   printf("current Dir:%s\n",curDir);

   return 0;  
}  
  
int normalCMD(char * args[]){  
   int pid = 0;  
   int status = 0;  
   pid = fork();  
   if(pid == 0){  
     if(execvp(args[0], args) < 0){    
             fprintf(stderr,"execvp error.......\n");   
             exit(1);    
     }    
   }  
   waitpid(pid, &status, 0);  
   return status;  
  
}   
  
   
/** 
deal the cmd 
*/  
int handlerCmd(char *cmd){  
    int cmdnum;    
    char *args[100];    
    int argnum;    
   
    argnum = parserCMD(args, cmd);    
    args[argnum] = NULL;   
    char *firstCmd = args[0];  
    int cmdType = getCmdType(firstCmd);  


    switch(cmdType){  
        case SHELL_BUILDIN_CD:  
            buildInCDCMD(args);  
            break;  
        case SHELL_NORMAL:  
            normalCMD(args);  
            break;  
      
    }  
  
}  
  
 
int main(){  
   char cmd[BUFFSIZE];  
   printf("enter a shell cmd (quit to exit)\n");
   while(1){  
        memset(cmd,0,sizeof(cmd));  
        int readCnt = 0;  
        readCnt = read(STDIN_FILENO,cmd,BUFFSIZE);  
        if(readCnt < 0){  
            fprintf(stderr,"read cmd failed and exit(-1)\n");  
            exit(-1);  
        }  
           
        if(isQuitCmd(cmd)){  
            break;  
        }  
          
        handlerCmd(cmd); 
		printf("enter new shell cmdi (quit to exit )\n");
   }  
   return 0;  
}  

#include <stdio.h>  
#include <string.h>  
#include <stdlib.h>  
#include <errno.h>  
#include <fcntl.h>  
#include <unistd.h>  
#include <sys/types.h>  
#include <sys/stat.h>  
#include <sys/wait.h>

#define SHELL_BUILDIN_CD 1  
#define SHELL_NORMAL 2  


#define BUFFSIZE 256;

/**
using quit cmd to exit
*/
int isQuitCmd(char * arg){
    static char *quit = "quit";
	return strcmp(arg,quit) == 0 ? 1 : 0;

}

/**
decide whether the cmd is build-in or normal
*/
int getCmdType(char *firstCmd){
   if(strcmp(firstCmd == "cd" )){
	 return SHELL_BUILDIN_CD;
   }else{
	 return SHELL_NORMAL;
   }


}


/**
deal the cmd
*/
int handlerCmd(char *cmd){
	int cmdnum;  
    char *args[100];  
    int argnum;  
 
    argnum = parserCMD(args, cmd);  
    args[argnum] = NULL; 
	char *firstCmd = args[0];
	int cmdType = getCmdType(firstCmd);
	
	switch(cmdType){
		case SHELL_BUILDIN_CD:
			buildInCDCMD();
			break;
		case SHELL_NORMAL:
		    normalCMD();
			break;
	
	}

}

int buildInCDCMD(char * args[]){
   char curDir[BUFFSIZE];
   char first = args[1][0];
   if(first != '/' && first != '.'){
      //concat the cd args with current dir
      getcwd(curDir, BUFFSIZE);
	  strncat(curDir,"/",BUFFSIZE - strlen(curDir));
   }
   strncat(curDir,args[1],BUFFSIZE - strlen(curDir));
   
   if(chdir(curDir) == -1){
	 fprintf(stderr,"chdir fail.......");
   }
   return 0;
}

int normalCMD(char * args[]){
   int pid = 0;
   int status = 0;
   pid = fork();
   if(pid == 0){
	 if(execvp(args[0], args) < 0){  
           	 fprintf(stderr,"chdir fail......."); 
             exit(1);  
     }  
   }
   waitpid(pid, &status, 0);
   return status;

} 

int parserCMD(char * cmdArray[], char *argv){
	int cnt = 0;
	char *p = strtok (argv, " ");
    while(p != NULL)
    {
              strcpy(cmdArray[cnt],p);
              cnt++;
              if(p!=NULL)
              p = (char *)strtok(p+strlen(p)+1," ");
    }
	return cnt;
}


int main(int argc, char *[]argv){
   char cmd[BUFFSIZE];
   while(1){
		memset(cmd,0,sizeof(cmd));
        int readCnt = 0;
		readCnt = read(STDIN_FILENO,cmd,BUFFSIZE);
		if(readCnt < 0){
			fprintf(stderr,"read cmd failed and exit(-1)");
			exit(-1);
		}
         
        if(isQuitCmd(cmd)){
			break;
		}
        
        handlerCmd(cmd);		
   }

}