Changing a file inline on Windows

Ruby
1

Here is my current method for editing files:

filename = File.join(‘path’, ‘to’, ‘file’)
content = []
File.open(filename, ‘r’) do |file|
content = file.readlines
end

content.collect! do |line|
line.gsub!(/six/, “half a dozen”)
line.chomp
end

File.open(filename, ‘w’) do |file|
file.write content.join($/)
end

This is expensive though, as it rewrites the entire file, even if only a
single word in the whole file is changed. I’m wondering if there is a
better way to do this.

James

2

On 22.06.2008 06:16, James D. wrote:

content.collect! do |line|
line.gsub!(/six/, “half a dozen”)
line.chomp
end

File.open(filename, ‘w’) do |file|
file.write content.join($/)

This is a killer because it will transform the whole file into a single
String just for printing. You better do either of this

  1. just do “file.puts content”

  2. work with String the whole way, i.e.

content = File.read file_name
content.gsub! /six/, “half a dozen”
File.open(file_name, “w”) {|io| io.write content}

First alternative has the advantage of being a smaller change to your
code and also I believe it’s nicer to the GC; second solution has the
advantage that you can do multiline replacements.

end

This is expensive though, as it rewrites the entire file, even if only a
single word in the whole file is changed. I’m wondering if there is a
better way to do this.

For text files the situation is usually this: the replacement has
different length than the original. Thus, you need to at least rewrite
all the stuff from the original string’s starting position on. The code
becomes a bit more complex and if the file is small it’s probably not
worthwhile.

Note also that there is command line option -i which will allow for easy
inline edits:

ruby -i.bak -pe ‘gsub /six/, “half a dozen”’ your_file

You can also use it in scripts:

#!/bin/ruby -i.bak -p
gsub /six/, “half a dozen”

Kind regards

robert

3

You can use the rio library to simplify this

require ‘rio’
rio(f) <f.contents.gsub(/six/,“half a dozen”)

4

On Jun 21, 11:16 pm, James D. [email protected] wrote:

content.collect! do |line|
This is expensive though, as it rewrites the entire file, even if only a
single word in the whole file is changed. I’m wondering if there is a
better way to do this.

James

Posted viahttp://www.ruby-forum.com/.

There was a small error in my previous post. Here a more complete
script

require ‘rio’
ario = rio(filename)
ario < ario.contents.gsub(/six/, “half a dozen”)

5

Thanks for all the information. I’ll try out these methods and try to
get an idea which one I like best.

James