At work, we are starting to refactor some of our system utilities. The scripts interact with these basic components:
- Postgres databases
- FTP servers
- Files on various servers
- Java applications
- Specific system calls
My boss, being from an "older generation" ;-), favors Unix scripting (sed, bash, etc.) . Being a Ruby/JRuby enthusiast myself, I wanted to show my team how easy these tasks are in JRuby. While sed might take fewer characters in some cases, I think JRuby strikes an ideal match between terseness and readability.
Note that the following code will not run on your computer, at least not without setting up a Postgres database and changing the FTP server info, etc. But it will give you a good flavor for system programming in JRuby.
#
# Copyright 2007 Effectiveqa.com. All rights reserved
#
def postgres
# Accessing Postgres from JRuby
# http://ruby.scripting.ca/postgres/rdoc/
$LOAD_PATH << 'C:/jruby-1.0.1/lib/ruby/gems/1.8/gems/postgres-pr-0.4.0/lib'
require 'postgres'
con = PGconn.connect('localhost', 5432, nil, nil, 'foo', 'postgres', 'password'
res = con.query("select * from bar")
puts res[0][0]
end
def ftp
# FTP Access
# http://ruby-doc.org/stdlib/libdoc/net/ftp/rdoc/index.html
require 'net/ftp'
Net::FTP.open('effectiveqa.com') do |ftp|
ftp.login('username', 'password')
ftp.chdir('public_html')
ftp.list('*.css').each {|file| puts file}
ftp.gettextfile('main.css', 'local_main.css')
end
end
def ftp_password
# Show how easily JRuby can handle password problem
require 'net/ftp'
begin
ftp = Net::FTP.open('effectiveqa.com')
ftp.login('effectiv', 'BADPASSWORD')
rescue
puts "Here is where I fix the password"
ftp.login('username', 'password')
ftp.chdir('public_html')
ftp.list('*.css').each {|file| puts file}
end
end
def file_tricks
# Different file/directory manipulations
# http://www.ruby-doc.org/stdlib/libdoc/fileutils/rdoc/index.html
require 'fileutils'
include FileUtils
begin cd('dfsdf') rescue puts 'Oops, had a problem...' end
chmod(0777, 'local_main.css')
puts "Don't match!" if ! cmp('local_main.css', 'local_main_1.css')
cp('local_main.css', 'local_main_copy.css')
puts "Do match!" if cmp('local_main.css', 'local_main_copy.css')
puts pwd
rm('local_main_copy.css')
begin rm('DOESNT_EXIST') rescue puts 'Caught one' end
end
def file_tests
# Very nice tests
# http://ruby-doc.org/docs/ProgrammingRuby/html/ref_m_filetest.html
puts FileTest.directory?('example.zip') # false
puts FileTest.size('example.zip') # 1723
puts FileTest.file?('.') # false
puts FileTest.file?('example.zip') # true
puts FileTest.readable?('example.zip') # true
puts FileTest.writable?('example.zip') # true
include FileTest
puts directory?('.') # true; needs include
puts file?('.') # false
end
def use_java
# Show off how easy it is to use Java from JRuby
include Java
zf = java.util.zip.ZipFile.new('example.zip')
puts "There are #{zf.size} files in the zip."
zf.entries.each {|entry| puts " file: #{entry}"}
end
def split_files
# Easy processing of DB dump files
lines = IO.readlines('pipeFile.txt')
lines.each {|line| puts line.split('|')[1]}
end
def system_calls
# JRuby has full access to OS calls
lines = `df`.split("\n")
lines.shift # Read off header line
lines.each do |line|
fields = line.split
next unless fields[0] =~ /C:$/ # Only care about the C: drive
percent = fields[4].to_i
puts "Holy cow, disk almost full" if percent > 95
puts "Disk > 50% full" if percent > 50
end
end
# Some interesting Ruby libraries
# http://beaver.net/slides/ruby/10-easy-pieces.html
# Library doc: http://www.ruby-doc.org/stdlib/
# Pathnames: http://www.ruby-doc.org/stdlib/libdoc/pathname/rdoc/index.html
# MD5, sha1: http://www.ruby-doc.org/stdlib/libdoc/digest/rdoc/index.html
# Waking trees: http://ruby-doc.org/stdlib/libdoc/find/rdoc/index.html
puts "\n**** I can access postgres\n"
postgres
puts "\n**** I can access FTP\n"
ftp
puts "\n**** I can tell if an FTP password failed\n"
ftp_password
puts "\n**** I have all kinds of *nix file commands\n"
file_tricks
puts "\n**** I also have all kinds of cool file tests\n"
file_tests
puts "\n**** I can easily use Java code\n"
use_java
puts "\n**** I can split up Dave's db dump files\n"
split_files
puts "\n**** I can make OS calls with ease\n"
system_calls
The only shortcoming I could find with JRuby is that it doesn't support all the command line options that Ruby does. So you can see that JRuby falls behind in the terseness of its one-liner to rip a particular field out of a pipe-delimited dump file, though I would argue it is more readable.
#> ruby -n -a -F"\|" -e "puts $F[1]" pipeFile.txt
#> perl -n -a -F"\|" -e 'print "$F[1]\n"' pipeFile.txt
#> jruby -e "IO.readlines('pipeFile.txt').each {|ln| puts ln.split('|')[1]}"
