execute-command.c

#include "command.h"
#include "command-internals.h"
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <error.h>
#include <fcntl.h>
/* FIXME: You may need to add #include directives, macro definitions,
   static function definitions, etc.  */

int
command_status (command_t c)
{
  return c->status;
}
void execute_simple(command_t c)
{
	int status;
	int fd2,fd3;
	pid_t pd = fork();
	if(pd == 0)
	{
	  if (c->input != NULL)
	    {
	      //	      fd = dup(0);
	      fd2 = open(c->input, O_RDONLY, 0644);
	      //printf("Input is %s, fd2 is %d", c->input, fd2);
	      if(dup2(fd2, 0)<0)
			  exit(1);
	    }
	  if (c->output != NULL)
	    {
	      fd3 = open(c->output, O_CREAT | O_TRUNC | O_WRONLY, 0644);
	      if(dup2(fd3, 1)<0)
			  exit(1);
	    }
	  if( c->u.word[0][0] == 'e' &&
	      c->u.word[0][1] == 'x' &&
	      c->u.word[0][2] == 'e' && 
	      c->u.word[0][3] == 'c' &&
	      c->u.word[0][4] == '\0')
	    execvp(c->u.word[1],&(c->u.word[1]));
	  else 
	      execvp(c->u.word[0],c->u.word);
	}
	else
	{
		waitpid(pd,&status,0);
		c->status = WEXITSTATUS(status);
		
	}
}

void execute_andor(command_t c,bool time_travel)
{
	int status;
	pid_t pd = fork();
	if((pd == 0))
	{
		execute_command(c->u.command[0],time_travel);
		int st = c->u.command[0]->status;
		if(st == 0)
		  exit(0);
		else 
		  exit(1);
		//exit(c->u.command[0]->status);
	}
	else
	{
		waitpid(pd,&status,0);
		int j = WEXITSTATUS(status);
		if((c->type == AND_COMMAND && j == 0) 
			|| (c->type == OR_COMMAND && j != 0))
		{
			pid_t pd2 = fork();
			if(pd2 == 0)
			{
				execute_command(c->u.command[1],time_travel);
				int st = c->u.command[1]->status;
				if(st == 0)
				  exit(0);
				else 
				  exit(1);
				//exit(c->u.command[1]->status);
			}
			else
			{
				waitpid(pd2,&status,0);
				c->status = WEXITSTATUS(status);
			}
		}
		else 
			c->status = WEXITSTATUS(status);
	}
}

void execute_seq(command_t c, bool time_travel)
{
	
	pid_t pd = fork();
	if(pd == 0)
	{
		execute_command(c->u.command[0],time_travel);
		int st = c->u.command[0]->status;
		if(st == 0)
		  exit(0);
		else 
		  exit(1);
	}
	else 
	{
	  int status;
	  waitpid(pd,&status,0);
		pid_t pd2 = fork();
		if(pd2 == 0)
		{
			execute_command(c->u.command[1],time_travel);
			int st = c->u.command[1]->status;
			if(st == 0)
			  exit(0);
			else 
			  exit(1);
			//exit(c->u.command[1]->status);
		}
		else
		{
			waitpid(pd2,&status,0);
			c->status = WEXITSTATUS(status);
		}
	}
}

void execute_subshell(command_t c, bool time_travel)
{
  // pid_t firstPid = fork();
  //if (firstPid < 0)
  //error(1, errno, "fork failed");
  //if (firstPid == 0)
  //  {
  if (c->output != NULL)
    {
      int fd = open(c->output, O_CREAT | O_TRUNC | O_WRONLY, 0644);
      dup2(fd, 1);
    }
      execute_command(c->u.subshell_command, time_travel);
    
      //  int st = c->u.subshell_command->status;
      //if (st == 0)
      //	exit(0);
      //else
      //	exit(1);
      // }
      // else
      // {
      //int status;
      //waitpid(firstPid, &status, 0);
      c->status = c->u.subshell_command->status;
      //}
}

void execute_pipe(command_t c, bool time_travel)
{
  int fd[2];
  pipe(fd);
  pid_t firstPid = fork();
  if (firstPid == 0) // first child
    {
      close(fd[1]);
      dup2(fd[0],0);
      execute_command(c->u.command[1], time_travel);
      int st = c->u.command[1]->status;
      if (st == 0)
	exit(0);
      else
	exit(1);
    }
  else
    {
      pid_t secondPid = fork();
      if (secondPid == 0)
	{
	  close(fd[0]);
	  dup2(fd[1],1);
	  execute_command(c->u.command[0], time_travel);
	  int st = c->u.command[0]->status;
	  if (st == 0)
	    exit(0);
	  else
	    exit(1);
	}
      else
	{
	  close(fd[0]);
	  close(fd[1]);
	  int status;
	  waitpid(-1, &status, 0);
	  waitpid(-1, &status, 0);
	  int estatus = WEXITSTATUS(status);
	  c->status = estatus;
	}
    }
}
void
execute_command (command_t c, bool time_travel)
{
  time_travel = false;
  switch(c->type)
  {
	case SIMPLE_COMMAND:
	  execute_simple(c); break;
	case OR_COMMAND:
	case AND_COMMAND:
	  execute_andor(c, time_travel);	break;
	case SEQUENCE_COMMAND:
	  execute_seq(c,time_travel);break;
        case PIPE_COMMAND: 	
	  execute_pipe(c, time_travel); break;
        case SUBSHELL_COMMAND:	
	  execute_subshell(c, time_travel); break;
  }
}