Handling invalid options with OptionParser

Ruby
1

Hi there,

I wrote my own Wake on Lan Script in ruby that uses a Plist to look up
either target Mac address by selected printer or target MAC address by
server and I use option parser for this.

It all works fine if the arguments are input correctly, but if the
arguments are off you get something like this. -x is not declared in my
options and was a test to see how it did when it got something that it
didn’t recognize.

ruby test.rb -x
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1443:in
complete': invalid option: -x (OptionParser::InvalidOption) from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1441:incatch’
from
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1441:in
complete' from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1280:inparse_in_order’
from
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1247:in
catch' from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1247:inparse_in_order’
from
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1241:in
order!' from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1332:inpermute!’
from
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/optparse.rb:1353:in
`parse!’
from test.rb:4

It’s not the end of the world as if the options are wrong then it won’t
do anything anyway, but I was wondering if anyone could tell me if
there’s any method in the class or extra thing I could do to catch dodgy
arguments and output the help file or the banner rather than this
inelegant list of errors?

Thanks in advance.

2

Stefano, that’s a very big help, thank you very much!

Adam

3

Alle Saturday 18 October 2008, Adam P. ha scritto:

from
parse.rb:1241:in `order!’
there’s any method in the class or extra thing I could do to catch dodgy
arguments and output the help file or the banner rather than this
inelegant list of errors?

Thanks in advance.

I guess you can enclose the call to OptionParser#parse! in a
begin/rescue
expression, rescuing OptionParser::InvalidOption or
OptionParser::ParseError
(which is the parent of InvalidOption) and display an error message.
Here’s a
simple example of how you can do it:

require ‘optparse’

o = OptionParser.new do |o|
o.banner = “test usage: test [OPTIONS]”
o.on(’-o’, ‘–option’, 'this option does nothing '){}
end

begin o.parse! ARGV
rescue OptionParser::InvalidOption => e
puts e
puts o
exit 1
end

the line

puts e

will display a message like

invalid option -a

(where -a is the invalid option passed to the script). The line

puts o

will display the usage message.

exit 1

will make the script exit with the error code 1.

I hope this helps

Stefano

4

PennyMBP:~ adam$ wopol -l
invalid option: -l
Usage: wopol [options]
-s, --server SERVERNAME
-p, --printer PRINTERNAME
-w, --wait SECONDS

Thought you might like to see the result after implementing your
suggestion. :smiley: Thanks again.