From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-05-11T15:41:27+09:00
Subject: Re: Problem renaming files

On Tue, May 11, 2010 at 5:10 AM, Jacob Davis <ismyhc@gmail.com> wrote:
> Hi Everyone,
>
> Im new to ruby and am having a hard time with something Im working on.
>
> I want to write a script that takes file names as arguments, then uses
> gets to get two values, and then renames the files based on those
> values.
>
> example:
>
> I want to rename mulitple files, removing the build number, and
> replacing it with another number.
>
> engine.105   -> rename to engine.8
>
> Anyways, so right now Im just working on doing this with one file at a
> time. I realize this could be done without a script, but I want to end
> up doing this with multiple files at once. My script is probably not the
> most efficient way either, but I'd just like to know what Im doing wrong
> with how Im doing it. Just so I can learn..
>
> Below is the code.. I run the file as:
>
> ruby c.rb engine.105
>
> I then enter the build number which is 105
> Next I enter the version number I want to replace the build number with
> which is 5
>
> The following is what I get:
>
> c.rb:14:in `rename': No such file or directory - engine.5 or 5
> (Errno::ENOENT)
>  from c.rb:14
>
>
> =====================
>
> #!/usr/bin/env ruby
>
> # Filename arguments
> file_names = ARGV.dup.to_s
>
> # Have user input build number to be removed
> puts "Please enter the build number you wish to be removed from the
> file"
> build_number = STDIN.gets.chomp.to_s
>
> # Have user input version number to be appended to file name
> puts "Please enter the version number you wish to be appended"
> version_number = STDIN.gets.chomp.to_s
>
> # Rename file replacing build number with version number
> File.rename(file_names, file_names[build_number]= version_number)
>
> puts "done!"

There are two problems here. The first one is that
file_names[build_number] = version will return the right hand side
expression, not the new value of the string, so you will be passing a
"5" to the rename method, not "engine.5". The second is that by
calling []= on file_names you are changing the object referenced by
file_names, not making a new one, so you are passing "engine.5" as the
first argument to rename. Try this instead:


# Rename file replacing build number with version number
new_name = file_names.dup
new_name[build_number] = version_number
File.rename(file_names, new_name)

Also, when you change things to receive multiple file names as
arguments to your script, you should probably change this line:

file_names = ARGV.dup.to_s

because that will join all the file names into a single string, which
is not what you want, I think.

Jesus.