Executing program from command line

Question

I have done a program that sends requests to a url and saves them in a file. The program is this, and is working perfectly:

require 'open-uri' 
n = gets.to_i 
out = gets.chomp
output = File.open( out, "w" )
for i in 1..n
 response = open('http://slowapi.com/delay/10').read
 output << (response +"\n")
 puts response
end
output.close

I want to modify it so that I can execute it from command line. I must run it like this:

fle --test abc -n 300 -f output

What must I do?

• Rajarshi Das: I do not understand what you exactly want but tell you you can use irb to run each and every line of your code
• sawa: Please use English punctuation when writing in English.

Answer 1

Something like this should do the trick:

#!/usr/bin/env ruby
require 'open-uri'
require 'optparse'
# Prepare the parser
options = {}
oparser = OptionParser.new do |opts|
 opts.banner = "Usage: fle [options]"
 opts.on('-t', '--test [STRING]', 'Test string') { |v| options[:test] = v }
 opts.on('-n', '--count COUNT', 'Number of times to send request') { |v| options[:count] = v.to_i }
 opts.on('-f', '--file FILE', 'Output file', :REQUIRED) { |v| options[:out_file] = v }
end
# Parse our options
oparser.parse! ARGV
# Check if required options have been filled, print help and exit otherwise.
if options[:count].nil? || options[:out_file].nil?
 $stderr.puts oparser.help
 exit 1
end
File::open(options[:out_file], 'w') do |output|
 options[:count].times do
 response = open('http://slowapi.com/delay/10').read
 output.puts response # Puts the response into the file
 puts response # Puts the response to $stdout
 end
end

• omninonsense: @Skynet then you should follow these instructions on how to register .rb files to be opened by the ruby binary. I am not aware of any other way. If you don't want the .rb suffix, you might need to be reqired to wrap your script call in a bach file. I am not a windows user, so I don't know the details.
• Skynet: can you update your code with an example of my code ? I don't understand exactly, how this works.

Answer 2

Here's a more idiomatic way of writing your code:

require 'open-uri' 
n = gets.to_i 
out = gets.chomp
File.open(out, 'w') do |fo| 
 n.times do
 response = open('http://slowapi.com/delay/10').read
 fo.puts response
 puts response
 end
end

This uses File.open with a block, which allows Ruby to close the file once the block exits. It's a much better practice than assigning the file handle to a variable and use that to close the file later.

How to handle passing in variables from the command-line as options is handled in the other answers.

• omninonsense: There's a small typo in the code example:n.times should be n.times do. I tried to edit it, but it wouldn't let me because the edit was under 6 characters. :(
• the Tin Man: @destielstarship, It's good that it didn't let you. It's considered bad form to edit people's code. Instead you should simply point it out in a comment. It's OK to adjust spelling, grammar and content for clarity but code and data are sacred.
• omninonsense: Oh, I wasn't aware of that SO convention! I apologise. :-)

Answer 3

The first step would be to save you program in a file, add #!/usr/bin/env ruby at the top and chmod +x yourfilename to be able to execute your file.

Now you are able to run your script from the command line.

Secondly, you need to modify your script a little bit to pick up command line arguments. In Ruby, the command line arguments are stored inside ARGV, so something like

ARGV.each do|a|
 puts "Argument: #{a}"
end

allows you to retrieve command line arguments.

• omninonsense: @MaxWilliams I also believe, they could just use #!/usr/bin/env ruby, but otherwise it is a good remark in case ruby was installed through MRI or similar.
• the Tin Man: Walking through ARGV is definitely old-school. Don't do it unless you absolutely have to. Instead, take advantage of using Ruby's built-in Option Parser class.