Example 9-7. lst

  #!/usr/bin/perl
  # lst - list sorted directory contents (depth first)
  
  use Getopt::Std;
  use File::Find;
  use File::stat;
  use User::pwent;
  use User::grent;
  
  getopts("lusrcmi")                            or die << DEATH;
  Usage: $0 [-mucsril] [dirs ...]
   or    $0 -i [-mucsrl] < filelist
  
  Input format:
      -i  read pathnames from stdin
  Output format:
      -l  long listing
  Sort on:
      -m  use mtime (modify time) [DEFAULT]
      -u  use atime (access time)
      -c  use ctime (inode change time)
      -s  use size for sorting
  Ordering:
      -r  reverse sort
  NB: You may only use select one sorting option at a time.
  DEATH
      
  unless ($opt_i || @ARGV) { @ARGV = (".") }
  
  if ($opt_c + $opt_u + $opt_s + $opt_m > 1) {
      die "can only sort on one time or size";
  }
  
  $IDX = "mtime";
  $IDX = "atime" if $opt_u;
  $IDX = "ctime" if $opt_c;
  $IDX = "size"  if $opt_s;
  
  $TIME_IDX = $opt_s ? "mtime" : $IDX;
  
  *name = *File::Find::name;  # forcibly import that variable
  
  # the $opt_i flag tricks wanted into taking
  # its filenames from ARGV instead of being
  # called from find.
  
  if ($opt_i) {
       *name = *_;  # $name now alias for $_
       while (<>) { chomp; &wanted; }   # ok, not stdin really
  }  else {
      find(\&wanted, @ARGV);
  }
  
  # sort the files by their cached times, youngest first
  @skeys = sort { $time{$b} <=> $time{$a} } keys %time;
  
  # but flip the order if -r was supplied on command line
  @skeys = reverse @skeys if $opt_r;
  
  for (@skeys) {
      unless ($opt_l) {  # emulate ls -l, except for permissions
          print "$_\n";
          next;
      }
      $now = localtime $stat{$_}->$TIME_IDX( );
      printf "%6d %04o %6d %8s %8s %8d %s %s\n",
              $stat{$_}->ino( ),
              $stat{$_}->mode( ) & 07777,
              $stat{$_}->nlink( ),
              user($stat{$_}->uid( )),
              group($stat{$_}->gid( )),
              $stat{$_}->size( ),
              $now, $_;
  }
  
  # get stat info on the file, saving the desired
  # sort criterion (mtime, atime, ctime, or size)
  # in the %time hash indexed by filename.
  # if they want a long list, we have to save the
  # entire stat object in %stat.  yes, this is a
  # hash of objects
  sub wanted {
      my $sb = stat($_);  # XXX: should be stat or lstat?
      return unless $sb;
      $time{$name} = $sb->$IDX( );  # indirect method call
      $stat{$name} = $sb if $opt_l;
  }
  
  # cache user number to name conversions; don't worry
  # about the apparently extra call, as the system caches the
  # last one called all by itself
  sub user {
      my $uid = shift;
      $user{$uid} = getpwuid($uid) ? getpwuid($uid)->name : "#$uid"
          unless defined $user{$uid};
      return $user{$uid};
  }
  
  # cache group number to name conversions; ditto on unworryness
  sub group {
      my $gid = shift;
      $group{$gid} = getgrgid($gid) ? getgrgid($gid)->name : "#$gid"
          unless defined $group{$gid};
      return $group{$gid};
  
  
  
  
  }