#include  <stdio.h>
#include  <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <wait.h>

#include <fcntl.h>
#include <unistd.h>



void  execute(char **argv,int background_flag,char output_file[30],char input_file[30])
{
	pid_t  pid;
	int    status;
	int j=0;
	int exe_process;
	int fdin,fdout;

     	if ((pid = fork()) < 0)       /* fork a child process           */
	{
          	printf("ERROR: forking child process failed\n");
          	exit(1);
     	}
     	else if (pid == 0)           /* child process:         */
	{
		printf("\033[35m\033[1m[ %d ]\033[m\033[m\n",getpid());
		

		if(strcmp(output_file,"\0"))
		{
                	if ((fdout = open(output_file,O_WRONLY|O_CREAT|O_TRUNC)) == -1)
			{
				fprintf(stderr," Could not open file %s for writing.\n",output_file);
				exit(1);
			}
	               	if ( dup2(fdout,STDOUT_FILENO)== -1)
			{
				fprintf(stderr,"dup2 Error");
			}
	                close(fdout);
		}



                if(strcmp(input_file,"\0"))
                {
                        if ((fdin = open(input_file,O_WRONLY)) == -1)
                        {
                                fprintf(stderr," Could not open file %s for reading.\n",input_file);
                                exit(1);
                        }
			printf("fdin=%d\n",fdin);
                        if ( dup2(fdin,STDIN_FILENO)== -1)
                        {
                                fprintf(stderr,"dup2 Error");
                        }
                        close(fdin);
                }




		if (execvp(*argv, argv) < 0)       /* execute the command  */
		{
               		printf("ERROR: exec failed\n");
               		exit(1);
        	}	
     	}
     	else 	                                   /* parent:      */
	{
       		if (background_flag==0)   
		{
		           if (strcmp(output_file,"\0"))	close(fdout);
		           if (strcmp(input_file,"\0")) close(fdin);
			while (wait(&status) != pid);
			if (!WIFEXITED (status))
			{
				printf ("the child process exited abnormally from signal %d\n",WTERMSIG(status ) );
			}
		}


	}
}

int  main(void)
{
char  read_line[1024];
char output_file[30];
char input_file[30];
char* arg_list[10];
int i,background_flag,status;
pid_t pid;


while (1) 
{                  
	i=0;
	strcpy(output_file,"\0");
	strcpy(input_file,"\0");
	background_flag=0;
	printf("\033[44m\033[1mUser_Shell:\033[m\033[m");	


        gets(read_line);            

	//clean zombie proccess
	while (((pid=waitpid(-1,&status,WNOHANG))!=-1)&&(pid!=0))	
		printf("\033[32m\033[1m[ %d ]:Done\033[m\033[m\n",pid);


	if (read_line[0]!=NULL)
{
        arg_list[i] = strtok(read_line," ");
	while (arg_list[i]!= NULL)
	{
		if (!strcmp(arg_list[i],"&")) background_flag=1;
		else if (!strcmp(arg_list[i],">"))
		{	
			arg_list[i]=strtok(NULL," ");
			strcpy(output_file,arg_list[i]);
		}
		else if (!strcmp(arg_list[i],"<"))
		{
			arg_list[i]=strtok(NULL," ");
			strcpy(input_file,arg_list[i]);
		}
		else ++i;
		arg_list[i]=strtok(NULL," ");
	}	


          if (strcmp(arg_list[0], "exit") == 0) 
             exit(0);   



          execute(arg_list,background_flag,output_file,input_file);          
}

     }
return 0;
}