#!/usr/local/bin/perl
#
# Simple-minded little Perl 4 script to extract specific files from the tar
# file that contains the Database for Galaxy Evolution Modeling, Leitherer
# et al., PASP, 108, 996, on the AAS CD-ROM Series, Volume VII.
#
# AUTHOR: Lee E. Brotzman, Advanced Data Solutions
#
# USAGE NOTES
#
# The script assumes that it is being started from the CD-ROM directory
# that contains the tar file, table of contents, and this script.
# The user provides the script with the output directory to extract
# the files into and the prefix for the files.  One should consult table.doc
# in this directory for a listing of the components of the database and their
# prefixes.
#
# If your system does not set execute permission for files on CD-ROM,
# or if your version of perl is in a location other /usr/local/bin/perl,
# you can invoke the script directly as follows:
#
#       $ perl extract.pl output-dir prefix
#
# See the usage message below.
#
# This script has been tested under perl4.036 and perl5.001 under Solaris and
# Linux; it should work pretty well under other OS's, too, except possibly a
# DOS/Windows or Mac system without Perl or tar programs.  The algorithm is
# quite simple: it compares the given prefix against the database directory
# listing in the file database.toc.  Every matching file name is saved in a
# list and then the tar command is used to extract only those files.

require 'pwd.pl';               # Use the old-style directory handler
&initpwd;
$cdrom_dir = $ENV{'PWD'};       # What is this directory path?

if ($#ARGV < 1) {               # Print usage if no arguments given
    print "Usage: perl extract.pl output-dir prefix\n";
    print "Example: perl extract.pl ~/database ALRV\n";
    exit 0;
}

die "Output directory $ARGV[0] does not exist?!" unless -d $ARGV[0];

# Load the file names from the table of contents
$files = &loadTOC($ARGV[1]);

die "No files matching $ARGV[1] found ?!" unless length($files);

# Now change to the output directory and extract the requested files
&chdir($ARGV[0]);
$database = "$cdrom_dir/database.tar";

system("tar -xvf $database $files");
exit;

# This subroutine will either return an array of filenames or a scalar string
# of blank-separated filenames, depending on the context.
sub loadTOC {
    local($prefix) = shift;
    # Just in case the user used the trailing asterisk that appears in the
    # list of datasets in table.doc, trim it off here (it will mess with
    # the pattern matching)
    chop($prefix) if $prefix =~ /\*$/;
    open(TOC, "$cdrom_dir/database.toc") ||
      die "Could not open file $cdrom_dir/database.toc";
    local(@files);
    local($line);
    $line = <TOC>;              # Skip the first line
    while ($line = <TOC>) {     # Go through each line and snip the file name
        chop $line;
        if ($line =~ /.{45}$prefix/) { # Save the name if it matches the prefix
            push(@files, substr($line,45));
        }
    }
    return wantarray ? @files : join(' ', @files);
}