#!/usr/bin/perl
use strict;
use warnings;
use utf8;

sub options {
    die "usage: $0 <user> <password> <host> <database>\n" if scalar(@ARGV) != 4;

    return {
        user => $ARGV[0],
        password => $ARGV[1],
        host => $ARGV[2],
        database => $ARGV[3],
    };
}
sub mysql_command {
    my $options = shift;
    my $command = "mysql -u $options->{user} ";
    $command .= "-p$options->{password} " if $options->{password};
    $command .= "-h $options->{host} " if $options->{host};
    $command .= "$options->{database}";
    return $command;
}
my $options = options();

my $command = "echo show tables | " . mysql_command($options);
my @tables = split(/\s/, `$command`);
for my $t (@tables) {
    print "=== $t ===\n";
    my $command = "echo show columns from $t | " . mysql_command($options);
    my @columns = split(/\n/, `$command`);
    for my $line (@columns) {
        print "$t\t$line\n";
    }
    print "\n";
}