From: Robert Klemme <shortcutter@...>
Date: 2008-10-26T00:24:53+09:00
Subject: Re: Join all text files in a folder, with a single line of Ruby code

On 25.10.2008 15:47, William James wrote:
> luisbebop wrote:
> 
>> I did a single line of code in Ruby, which joins all text files in a
>> folder to a bigfile. I got some tests, and it's works!
>> Does anyone knows a better way, or other 'Ruby Way' to do that ?
>>
>> File.open('bigfile','w') { |mergedFile| Dir.glob("*.txt").each { |
>> file| File.readlines(file).each { |line| mergedFile << line } } }
> 
> "We don't need no stinkin' loops!"
> 
> ruby -e"puts ARGF.to_a" *.txt >merged

There's also

ruby -e '$defout.write(ARGF.read)' *.txt >merged
ruby -e 'File.open("out","w") {|io| io.write(ARGF.read)}' *.txt

> "We still don't need no stinkin' loops!"
> 
> File.open("mrg","w"){|f|f.puts Dir['*.txt'].map{|nm|IO.read nm}}

That's vastly inefficient since it reads all the files into memory 
before writing a single byte.  This is not necessary.  You can at least 
improve to

File.open("mrg","w"){|f|Dir['*.txt'].each{|nm|f.write(File.read(nm))}}

But a proper solution (i.e. one that deals with arbitrary large files) 
would use a fixed buffer size - but that looks ugly on a single line...

Kind regards

	robert