// try running commands '/bin/ls / > abcde'
// '/bin/cat < abcde'

#include <fcntl.h>
#include <unistd.h>
#include <iostream>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
using namespace std;

void runcommand(char *cmd, char*argv[], char* readfile, char* writefile) {
  
  int status, i;
  cout << "cmd = " << cmd << "\n";
  i=0;
  while (argv[i]!= NULL) {
    cout << "argv[" << i << "] = " << argv[i] << "\n";
    i++;
  }
  cout << "readfile = " << readfile << "\n";
  cout << "writefile = " << writefile << "\n";
    if (fork() == 0) {
       if ((readfile != NULL) && (readfile[0] != '\0')) {
           int fd = open(readfile, O_RDONLY);
           if (fd == -1) {cerr << "error\n", exit(0);}
           close(0); dup(fd); close(fd);
       }
       if ((writefile != NULL) && (writefile[0] != '\0')) { 
           int fd = open(writefile, O_CREAT | O_WRONLY, 00777);
           if (fd == -1) {cerr << "error\n", exit(0);}
           close(1); dup(fd); close(fd);
        }
        int stat = execv(cmd, argv);
        if (stat == (-1)) {cerr << "error\n", exit(10);}
    }
     int stat = wait(&status);
     if (stat == -1) {cerr << "error return from wait\n";}
}
// example6.cpp

int  main() 
{
  char buf[1000];
  char cmd[100];
  int i, j, k;
  char arg[10][100];
  char *argv[10];
  char readfile[100];
  char writefile[100];

  while (fgets(buf, 1000, stdin)) {
    for (i=0; i<10; i++) arg[i][0] = '\0';
    readfile[0] = '\0';
    writefile[0] = '\0';
    // my assumption about the command is 
    // (1) first word is always the command
    // (2) ">" and "<" are separated by a space from other words
    // (3) "<" and ">" are used correctly
    // (4) There are at most ten words in a line

    i = sscanf(buf, "%s %s %s %s %s %s %s %s %s %s", arg[0], arg[1], arg[2],arg[3],arg[4],arg[5],arg[6],
	       arg[7],arg[8],arg[9]);
    for (k=0; k<i; k++) 
      cout << "arg[" << k << "] = " << arg[k] << "\n";

    for (j=1; j<i-1; j++) {
      if (strcmp(arg[j], ">") == 0) {
	strcpy(writefile, arg[j+1]);
	for (k = j+2; k<i; k++) strcpy(arg[k-2], arg[k]);
        i -= 2;
        break;
      }
    }

    for (j=1; j<i-1; j++) {
      if (strcmp(arg[j], "<") == 0) {
	strcpy(readfile, arg[j+1]);
	for (k = j+2; k<i; k++) strcpy(arg[k-2], arg[k]);
        i -= 2;
        break;
      }
    }

    for (j=0; j<i; j++) argv[j] = arg[j];
    argv[j] = NULL;
    if (strcmp(argv[0], "quit") == 0) exit(0);
    runcommand(argv[0], argv, readfile, writefile);
  }
  return 0;
}