Shell Programming and Scripting

  print `flush`;
  thank();        #print thank header
  use Getopt::Std;                # use declaration with the options function
   
  getopts("ld:") or usage() and exit;     #accept only options l and d
  $dOption = $opt_d;      #store the d option to a variable
  $lOption = $opt_l;      #store the l option to a variable
  $newDIR;
   
  #If there is no option selected
  if(X$lOption)
  {
          nooptionXX; #call nooption file
  }
   
  #if option l is entered
  elsXf($lOption)
  {
          loption();
  }
   
  # if option d is selected
  else
  {
          #display usage and exit
          XXXXX "\n";usage() ;"\n";
          exit X;
   
  }
   
  #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~SUB ROUTINES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   
   
  #openDIR subroutine
  #       -If -d option is not entered, then open the current directory.
  #       -If -d option is entered, then check and open if it is a valid directory.
  #       -Store all the files in the specify directory to an array
  XXX openDIR
  {
          XX($dOption)    #check if -d option is entered
          {
                  chomp($dOption);        #trim space
                  if(XX $dOption)         #check if it is a valid directory
                  {
                          chdir($dOption);#change to specify directory
                          opendir($THISDIR,$dOption);}    #open directory
                  #print out error message when invalid directory is entered
                  else {print "\n\t ==>\"$dOption\" is  Invalid Directory.\n\n";exit 1;}
          }
          else {opendir($THISDIR,".");}#open the specify directory
          @DIRLIST = readdir($THISDIR);#store all files to an array
  ********ADD A LINE TO SORT ALL FILES TO AN ARRAY*************
  }
   
  #nooption subroutine
  #       -print out the output when there is no option specify
  sub XXXXXXXX
  {
          openDIR();      #call openDIR() method
          XXXXX "File Names\n";#print header
          print "---------------\n";
          #print out the result
          foreach $result(@DIRLIST){if(-f $result){print "$result\n";}}
          closedir($THISDIR);#close directory.
          exit 1;
  }
   
  #l option subroutine
   
  XXX XXXXXXX
  {
          openDIR();      #call openDIR() method
          print "\n";
          #print header
          printf ("\%-25s", " File Name");
          printf ("\%7s", "Size");
          printf " ";
          printf ("\%-10s", "Owner");
          printf ("\%-15s\n", "Group");
   
          printf ("\%-25s", "------------- ");
          printf ("\%7s", "------");
          printf " ";
          printf ("\%-10s", "---------");
          printf ("\%-15s\n", "-----------");
          #print output
          forXXXX $result (@DIRLIST)
          {
                  if(XX $result) # Verify that the result is a file
                  {
                          $size  = -s $result;
                          $group = (stat($result))[5];
                          $group = getgrgid($group);
                          $user  = (stat($result))[4];
                          $user  = getpwuid($user);
   
                          #print out file name
                          printf ("\%-25s", "$result");
                          #File size = 7 space reserve, RIGHT Alignment
                          printf ("\%7s", "$size");
                          printf " ";
                          #File Owner = 10 spaces reserve, LEFT Agliment
                          printf ("\%-10s", "$user");
                          #File Group = 15 spaces reserve, LEFT Agliment
                          printf ("\%-15s\n", "$group");
                  }
   
          }
          closedir($XXXXXXX);
          exit 1;
   
  }
  #This is the HERE document which is used to display the usage error message
  sub XXXXX{
          print STDERR << "EOF";
          usage: $0 [-l][-d dir]
          -l : Display the long list(File Name, Size, Owner and Group.
          -d dir : scan directory.
          NOTE: all the options have to start with '-' sign.
  EOF
  }
  # This is the thank subroutine 
  sub XXXXX
  {
   
  #print out the header
  print `flush`;
  print `clear`;
   
  print "\n\n\n\n\n\n\n\n\t###################################\n";
  print "\t#    Thank for using our script   #";
  print "\n\t###################################\n\n";
   
  }