What jar is that friggin class in?!?!?!

It seems to me that one of the most common tasks I have to preform when packaging a J2EE project is to find out what jar a class I depend on is in.

I have written (multiple times now) a simple perl script that finds all the jars in a given directory and scans them for a file. Thanks to the power of regular expressions you can pass in either com.foo.bar.Class or com/foo/bar/Class which ever is easier to cut-n-paste from the java.lang.NoClassDefFoundError, or similar, stack trace.

#!/usr/bin/perl

$JAR_COMMAND = "jar";
#Uncomment to use fastjar instead
#$JAR_COMMAND = "fastjar";

$class = "";
$lookin = ".";
if(@ARGV < 1) {
    print "USAGE: \n\tclassfinder [dir to search fo jars]
<packageName>\n";
    exit;
} elsif (@ARGV > 1) {
  $lookin = $ARGV[0];
  $class = $ARGV[1];
} else {
  $class = $ARGV[0];
}

foreach $jar (`find $lookin -name '*\.jar'`) {
    chomp $jar;
    foreach $file (`$JAR_COMMAND -tf $jar`) {
        chomp $file;
        if($file =~ $class) {
            print "$jar:$file\n"}
    }
}

The script relies on the standard unix utility find, it works on unix, linux, osx and cygwin. If you have an easy way to do this without using find I’d love to see it.

Simple script for batching tasks in a multi-core/CPU envionment

Today I was tasked with keeping all four processors of a machine busy with CPU intensive processes (in this case transcoding video). I wrote a quick and dirty Perl script to keep running ffmpeg as input files became available, but never run more that four at a time. The script looks for .avi files in the directory from which it was executed. It then maintains a stack of file names, forks a child process for each file and moves it when done.

#!/usr/bin/perl

use POSIX ":sys_wait_h";
use Errno qw(EAGAIN);

$secs = 5;

$numProcs = 0;
$maxProcs = 4;

$fileExt = ".avi";

@files = ();
%was_processed = {};

while (1) {
    #print "numProcs = $numProcs\n";
    if($numProcs < $maxProcs) {
	$numProcs++;
	execNext();
    }
    my $reaped = reapNext();
    if($reaped > 0) {
	$numProcs--;
    } elsif ($numProcs == $maxProcs) {
	#print "Sleeping...\n";
	sleep $secs;
    }
}

sub reapNext {
    return waitpid(-1, &WNOHANG);
}

sub execNext() {
    my $file;
    WAIT_FOR_NEW_FILE: {
	getFiles();

	while($was_processed{$file = pop @files}) {}

	if(!defined $file) {
	    print "Waiting for new $fileExt files...\n";
	    sleep $secs;
	    redo WAIT_FOR_NEW_FILE;
	} else {
	  $was_processed{$file} = 1;
	}
    }
    doFork($file);
}

sub getFiles {
    if($#files == -1) {
	push @files, <*$fileExt>;
    }
}

sub doFork {
    my $file = @_[0];
  FORK: {
      if($pid = fork) {
	  #We are in the orig process
	  return;
      } elsif (defined $pid) {
	  #We are in a child process
	  doChild($file);
      } elsif ($! == EAGAIN) {
	  #Something is wonky, but we should be able to recover...
	  sleep 5;
	  redo FORK;
      } else {
	  die "Can't fork: $!\n";
      }
    }

}

sub doChild {
    my $file = @_[0];
    (my $name, my $junk) = split /$fileExt/, $file;
    print "Ripping $file\n";

    system "(ffmpeg -i \"$file\" -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -b 1500k -bf 2 -f mpegts -aspect 4:3 -y \"$name\.ts\" 2>&1) > \"$name\.log\"\n";
    system "(mv \"$file\" ripped  2>&1) >> \"$name\.log\"\n";

    #unlink "\"$name\.ts\.mpeg\"";#delete the ts file
    #sleep $secs + rand $secs;

    exit;
}