[ILUG] Debian package dependancies

[Mel]

I was looking to clean up packages I had installed on my system a bit
because there is a lot of them installed that I don't use at all. I was a
bit suprised there wasn't a tool around that would give me a dependancy
graph or reference count for packages. So, I wrote this woefully
inefficient nasty little perl script. Dont bother commenting on it's
efficiency, how it could have been better or how I could have written it
in one line, I'm not really interested :-) . It does the following

o Reference counts packages
o Prints out packages with only one reference to ./debian_package.single
o Produces a graph of package dependances with a reference count < 2 to
  ./debian_package.graph
o Generates a postscript file of graph with dot

It was ./debian_package.single I was interested in but when DEPTHRESHOLD
is set to something really high, it produces a mildly amusing, albeit
worthless (461 edges point to libc) graph.  Thought the script might be
of use to someone so here it is

#!/usr/bin/perl

use strict;

# Global variables
my $DEB_INSTALLED="/var/lib/dpkg/status";
my $GRAPH="./debian_package.graph";
my $SINGLECOUNT="./debian_package.single";
my $DEPTHRESHOLD=2;

# Input variables
my $line;
my $package;
my $dependlist;
my $depend;
my $dummy;
my $count=0;
my $status;
my %depcount;

# Open files
open (INPUT , $DEB_INSTALLED) || die ("Failed to open input file");
open (OUTPUT, ">$GRAPH") || die("Failed to open output file");
open (SINGLE, ">$SINGLECOUNT") || die("Failed to open output file");

# Print headers
print OUTPUT "digraph debian {\n";
print OUTPUT "node [ fontname=Helvetica,fontsize=8 ];\n";

# Read installed file and do a package reference count
print "Generating reference count\n";
$line=<INPUT>;
while (!eof(INPUT) )
{
  # Read to package
  while ($line !~ /^Package:/ && !eof(INPUT)) { $line = <INPUT>; }

  # Get package name
  chomp($line);
  ($dummy, $package) = split(/ /, $line);

  # Read status
  $line = <INPUT>;
  ($dummy, $status) = split(/ /, $line);
  if ($status eq "install")
  {

    # Read forward to depends
    while ($line !~ /Depends:/ && !eof(INPUT)) { $line = <INPUT>; chomp($line); }
    if (!eof(INPUT))
    {
      $dependlist = $line;
      $dependlist =~ s/Depends: //;

      # Reference count
      foreach $depend (split(/,/, $dependlist))
      {
        # Remove version
        $depend =~ s/\(.*\)//;

        $depcount{"$depend"}++;
      }
    }
  }
}


# Read installed file and print out depends
print "Generating graph\n";
seek INPUT, 0, 0;
$line=<INPUT>;
while (!eof(INPUT) )
{
  # Read to package
  while ($line !~ /^Package:/ && !eof(INPUT)) { $line = <INPUT>; }

  # Read status
  $line = <INPUT>;
  ($dummy, $status) = split(/ /, $line);
  if ($status eq "install")
  {

    # Get package name
    chomp($line);
    ($dummy, $package) = split(/ /, $line);

    # Print out if only single reference
    if ($depcount{$package} == 0) { print SINGLE "$package\n"; }

    # Read forward to depends
    while ($line !~ /Depends:/ && !eof(INPUT)) { $line = <INPUT>; chomp($line); }
    if (!eof(INPUT))
    {
      $dependlist = $line;
      $dependlist =~ s/Depends: //;

      # Print out depends list
      foreach $depend (split(/,/, $dependlist))
      {
        # Remove version
        $depend =~ s/\(.*\)//;

        # Output dependancy
        if ($depcount{"$depend"} < $DEPTHRESHOLD)
        {
          print OUTPUT "\"$package\" -> \"$depend (" . $depcount{"$depend"} . ")\";\n";
        }
      }
    }
  }
}

# Close graph
print OUTPUT "}\n";

# Generate graph
print "Generating graph postscript....\n";
system("dot -Tps $GRAPH -o dependancies.ps");


# Close files
close INPUT;
close OUTPUT;
close SINGLE;

-- 
Mel Gorman
MSc Student, University of Limerick
http://www.csn.ul.ie/~mel