#!/usr/bin/perl -w

use strict;

use File::Basename;
use Getopt::Long;
use Time::HiRes qw ( sleep );
use Pod::Usage;

$0 = basename $0;
my ($time,$file,$cmd,$verbose,$help,$many_cmds);

# read in the command line options
GetOptions( 'time=f'  => \$time,
            'multiple-cmds' => \$many_cmds,
            'help' => \$help,
            'verbose' => \$verbose ) || pod2usage(2);

# print a help message if requested
if ( $help ) {
   pod2usage( -verbose => 2 );
}

# exit with a help message if called incorrectly
if ( !$ARGV[0] || !$ARGV[1] ) {
   pod2usage(2);
}

# correctly split up the files and commands 
my ( @files,@cmds );
if ( $many_cmds ) {
   @cmds = split /,/, (pop @ARGV);
} else {
   @cmds = pop( @ARGV );
}

@files = @ARGV;

# correctly set $time if not set from the command line
if ( !$time ) { $time = 0.25 };
$SIG{'INT'}  = \&catch_sigint;

my %modtime; # keeps track of file modification times for each file
foreach my $file (@files) {
   $modtime{ $file } = (stat($file))[9];
   if ( $verbose ) {
      print "Watching $file, initial mtime is $modtime{$file}\n";
   }
}

      if ( $new != $modtime{$file} ) {
         $modtime{$file} = $new;
         if ( $verbose ) {
            print "$file last modified at $modtime{$file}.\n"
         } ;

         foreach my $cmd (@cmds) {
            print "Executing $cmd ... ";
            system( $cmd );
            print "done.\n";
         }
      }
   } }

###############
# Subroutines #
###############

sub catch_sigint { print STDERR "\nExiting $0 ...\n"; exit 1; }

#####################
# Usage Information #
#####################

=head1 NAME

helios - automatic file monitoring and command execution

=head1 SYNOPSIS

helios [options] file1 [file2 ...] command(s)

 options: --time number_of_seconds --verbose --multiple-cmds --help

=head1 OPTIONS

=item B<--multiple-cmds>

Indicates that a comma-separated list of commands is supplied on the
command line.  Each command will be executed in succession after a
file is modified.

=item B<--time>

Sets the time (in seconds) between checks of the filename. Defaults to
1 second.  Warning: accurate monitoring of time less than a second is
not guaranteed, see the Time::HiRes manpage fmodification times, and t
+he commands executed.

=head1 EXAMPLES

 # Monitor HelloWorld.java and HellWorld2.java, execute 'javac *.java'
 # when either of these has changed
 $ helios HelloWorld.java HelloWorld2.java 'javac *.java'

 # Monitor myFile.java, execute the commands 'javac *.java' and 'java
 # myFile' when the file has changed.
 $ helios --multiple-cmds myFile.java 'javac *.java','java myFile'

 # Monitor HelloWorld.java every 0.25 seconds, execute 'javac *.java
 # when the file has changed.
 $ helios --time 0.25 --verbose HelloWorld.java 'javac *.java'


=head1 DESCRIPTION

B<helios> will monitor a file for changes and execute a command
whenever that file changes. It is named after the Greek god Helios,
the god of sun and sight.

While multiple files can be separated by spaces, commands should
always be grouped into a single 

Development of B<helios> was inspired by the atchange program,
originally by Dr.  Tom Schneider:
<http://www.lecb.ncifcrf.gov/~toms/atchange.html>. 

B<helios> has a few advantages over the original atchange program:
   - Support for monitoring of multiple files
   - Support for executing multiple commands from the command-line
   - Support for changing the polling time of files
   - Better platform independence (less reliance on csh)

=head1 AUTHOR

Tex Thompson <tex@biosysadmin.com>

=head1 LICENSE

B<helios> is licensed under the GNU GPL license, available from
http://www.gnu.org/.

=cut