#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/wait.h>
 #include <sys/types.h>
#include <assert.h> 
int main(){

char *token;
char command[80];;
char **arglist, *str, *strl; 
 int i,j,n,val,status;
  printf( "At the prompt enter a command; Enter an empty line to quit\n");
  while(1){ 
    printf( "--->");       
    fgets(command, 80,stdin);
    //printf("input string is: %s\n",command);

    //Determine number of command line entries
    if (strlen(command) < 2) break;
    if (command[strlen(command)-2] == ' ') n=0;
    else n=1;
    strl=command-1;
    str=command;
    while ((str=index(str,' '))!=NULL){
       //printf("str=%s,strl=%s\n",str,strl);
      if ((strl+1 < str) && (*str != '\n')){
	n++;
	//printf("------%d\n",n);
      }
      strl=str;
      str=str+1;
    }
    n++; //add space for terminating 0
    //printf("n=%d\n",n);
    if (!(val=fork())){
         
      //parse string
      token = strtok(command, " ");
      i=0;
      arglist=(char **)malloc(n*sizeof(char*));
      while(token!=NULL){
  	  if ('\n' != *token){ 
             arglist[i++]=token;
             //printf("token=%s\n",token);
             token=strtok(NULL," ");
           }
           else break;        
      }
      arglist[i]=0;
      assert(i<=n);
      //printf("n=%d,i=%d\n",n);
      //printf("The parsed string is\n");  
      //for (j=0;j<i;j++) printf("\t %s\n",arglist[j]);
      if (arglist[i-1][strlen(arglist[i-1])-1]=='\n')
	  arglist[i-1][strlen(arglist[i-1])-1]=0;
      //printf("child process %d about to exec %s\n",getpid(),arglist[0]);
      fflush(stdout);
      execvp(*arglist,arglist);
      printf("exec failed\n" );
      //perror(command);
      fflush(stdout);
      exit(1);
    }
    else if (val < 0) perror("fork failed");
    else while((val=waitpid(0,&status,WNOHANG)>0)){
      printf("child process %d exited with status = %d\n",val,status);
      fflush(stdout); 
      }
    usleep(50000);
  }
  while((val=waitpid(0,&status,WNOHANG)>0)){
      printf("child process %d exited with status = %d\n",val,status);
      fflush(stdout); 
      }

}