Hi I have been testing some very basic things in ruby and discover the following.
If i put in a file called xxxx.rb in this path "C:\Documents and Settings\Desktop\xxxx.rb"
puts __FILE__
and invoke this ruby file in a command line WITHOUT preceding ruby the output is the following
C:/Documents and Settings/Desktop/xxxx.rb
but if i invoke the xxxx.rb file with ruby (ruby xxxx.rb) in the command like the output is the following:
xxxx.rb
Why is that difference?? Thanks
PD: I'M ON WINDOWS XP SP3
RUBY VERSION: 1.8.6
What you want is to expand the path properly:
# Affected by the current working directory, etc.
puts __FILE__
# Always an absolute path
puts File.expand_path(__FILE__, Dir.getwd)
This takes your current working directory into account.
I'm guessing that when you just double click on the file, the absolute path gets passed. You should achieve the same effect by calling it like:
ruby C:/Documents and Settings/Desktop/xxxx.rb
Related
I got a method where I use Dir.chdir(File.dirname(__FILE__)) inside. I am using it so that I can run the ruby file from anywhere and not get this error: No such file or directory # rb_sysopen - 'filename' (Errno::ENOENT).
Using the method for the first time works fine but using it for the second time throws an error. See method and exact error below.
def meth(string)
Dir.chdir(File.dirname(__FILE__))
hash = JSON.parse(File.read("file.json"))
# do something with hash and string
# return some value
end
meth("first string") # this returns what is expected
meth("second string") # this second usage of the method throws the error
Error sample pinpointing the line where I used Dir.chdir(File.dirname(__FILE__)):
dir/decoder.rb:44:in `chdir': No such file or directory # dir_s_chdir - lib (Errno::ENOENT)
Not sure if OS plays a role here, I am using an m1 BigSur on version 11.2.3.
Why is this happening?
What needs to be done so that the method` can be used as much as needed without running into the error?
Your problem here seems to be that __FILE__ is a relative path like dir/decoder.rb and that path becomes invalid after the first time Dir.chdir is used, because that command changes the working directory of your entire Ruby process. I think the solution would be to do something like this in your decoder.rb file:
DecoderDir = File.realpath(File.dirname(__FILE__))
def meth
Dir.chdir(DecoderDir)
# ...
end
I'm guessing that the first time the Ruby interpreter processes the file, that is early enough that the relative path in __FILE__ still refers to the right place. So, at that time, we generate an absolute path for future use.
By the way, a well-behaved library should not run Dir.chdir because it will affect all use of relative paths throughout your entire Ruby process. I pretty much only run Dir.chdir once and I run it near the beginning of my top-level script. If you're making a reusable library, you might want to do something like this to calculate the absolute path of the file you want to open:
DecoderJson = File.join(DecoderDir, 'file.json')
I'm working in an IRB shell on a dos CMD
I load a module from a mystuff file
require '.\mystuff'
I change the module in the mystuff file and I type again
require '.\mystuff'
How come the IRB does not pick up the changes in the file when I try to call functions or variables from the newest version of my mystuff module?
require will not load the same file twice. If you want to load the file again, you need to use load. See What is the difference between include and require in Ruby? for more information.
Your Syntax is Wrong
Ruby doesn't use backslashes. You need to use forward slashes, or use File#join.
Your $LOAD_PATH is Wrong
Your $LOAD_PATH (a.k.a $:) is wrong. You need to include the present working directory with:
$: << '.'
in irb, or use Kernel#require_relative in executable or sourced files.
I have written a couple of small Ruby scripts for system administration using Ruby 1.9.3. In one script I use:
File.dirname(__FILE__)
to get the directory of the script file. This returns a relative path, however when I call the script from a second script File.dirname returns an absolute path.
Ruby Doc lists an absolute return path in its example whereas I found a discussion on Ruby Forum where a user says dirname should only return a relative path.
I am using the suggested solution from Ruby Forums to use File.expand_path to always get the absolute path like this:
File.expand_path(File.dirname(__FILE__))
but is there a way to make the behaviour of dirname consistent?
UPDATE:
To expand on Janathan Cairs answer, I made two scripts:
s1.rb:
puts "External script __FILE__: #{File.dirname(__FILE__)}"
s0.rb:
puts "Local script __FILE__: #{File.dirname(__FILE__)}"
require './s1.rb'
Running ./s0.rb gives the following output:
Local script __FILE__: .
External script __FILE__: /home/kenneth/Pictures/wp/rip_vault
File.dirname should return an absolute path if given an absolute path, and a relative path if given a relative path:
File.dirname('/home/jon/test.rb') # => '/home/jon'
File.dirname('test.rb') # => '.'
__FILE__ returns the name of the current script, which is therefore a relative path from the current directory. That means you should always use expand_path if you want to get the absolute path with File.dirname(__FILE__).
NB Ruby 2.0.0 introduces the __dir__ constant
If you already upgraded to Ruby 2.0, you can use the new constant
__dir__
otherwise you can use
File.expand_path('..', __FILE__)
which is shorter than
File.expand_path(File.dirname(__FILE__))
File.expand_path documentation
I'm trying to include a source code file when I run irb but irb is unable to find it.
For example, say I am in the following directory in terminal:
/dan/rubyapp/
Assume I have a file named "firstapp.rb" in /dan/rubyapp/
I startup irb and from the irb prompt I type
> require "firstapp.rb"
but the file can't be found. If I type "Dir.pwd" it shows as
/dan/rubyapp/
The only way I can get "require" to work is if I include the full path like so
> require "/dan/rubyapp/firstapp.rb"
Is that the only way I can get this to work? All the tutorials I see online simply do "require file_name" so I assumed it would work.
here is the output from $: at irb
ruby-1.9.2-p0 > $:
=> ["/Users/Daniel/.rvm/gems/ruby-1.9.2-p0/gems/wirble-0.1.3/bin",
"/Users/Daniel/.rvm/gems/ruby-1.9.2-p0/gems/wirble-0.1.3/lib",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/x86_64-darwin10.4.0",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/vendor_ruby/1.9.1",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/vendor_ruby/1.9.1/x86_64-darwin10.4.0",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/vendor_ruby",
"/Users/Daniel/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1",
"/Users/Daniel/.rvm/rubies/ruby-
1.9.2-p0/lib/ruby/1.9.1/x86_64-darwin10.4.0"]
The problem is that the current working directory is no longer in your path (as of Ruby 1.9.2). There are a few different ways around the problem.
1) In a ruby file itself, you can use the method require_relative instead of require. This will load a file relative to the loaction of the file containing the require_relative method:
http://extensions.rubyforge.org/rdoc/classes/Kernel.html
require_relative 'firstapp.rb'
This, however, will not work in irb.
2) Your other option is to include the current path in your argument to the require method. This will work in irb or in a ruby file. For instance:
require './firstapp.rb'
The reason this was implemented in ruby was to avoid inadvertently requiring the wrong file if there are different files with the same name in different directories in the path (similar to how *nix does not include the current directory "." in its path)
A couple of things to try:
1) Drop the .rb from the end of your require so you have:
require 'firstapp'
You don't normally add the .rb to a require (only to a load) - have a look here for more details:
http://www.fromjavatoruby.com/2008/10/require-vs-load.html
2) Failing that, make sure the current directory is on your load path - in irb execute:
p $:
and it will print out your ruby load path - check for an entry for "." (mine is the last entry)
I see this all the time in Ruby:
require File.dirname(__FILE__) + "/../../config/environment"
What does __FILE__ mean?
It is a reference to the current file name. In the file foo.rb, __FILE__ would be interpreted as "foo.rb".
Edit: Ruby 1.9.2 and 1.9.3 appear to behave a little differently from what Luke Bayes said in his comment. With these files:
# test.rb
puts __FILE__
require './dir2/test.rb'
# dir2/test.rb
puts __FILE__
Running ruby test.rb will output
test.rb
/full/path/to/dir2/test.rb
The value of __FILE__ is a relative path that is created and stored (but never updated) when your file is loaded. This means that if you have any calls to Dir.chdir anywhere else in your application, this path will expand incorrectly.
puts __FILE__
Dir.chdir '../../'
puts __FILE__
One workaround to this problem is to store the expanded value of __FILE__ outside of any application code. As long as your require statements are at the top of your definitions (or at least before any calls to Dir.chdir), this value will continue to be useful after changing directories.
$MY_FILE_PATH = File.expand_path(File.dirname(__FILE__))
# open class and do some stuff that changes directory
puts $MY_FILE_PATH
__FILE__ is the filename with extension of the file containing the code being executed.
In foo.rb, __FILE__ would be "foo.rb".
If foo.rb were in the dir /home/josh then File.dirname(__FILE__) would return /home/josh.
In Ruby, the Windows version anyways, I just checked and __FILE__ does not contain the full path to the file. Instead it contains the path to the file relative to where it's being executed from.
In PHP __FILE__ is the full path (which in my opinion is preferable). This is why, in order to make your paths portable in Ruby, you really need to use this:
File.expand_path(File.dirname(__FILE__) + "relative/path/to/file")
I should note that in Ruby 1.9.1 __FILE__ contains the full path to the file, the above description was for when I used Ruby 1.8.7.
In order to be compatible with both Ruby 1.8.7 and 1.9.1 (not sure about 1.9) you should require files by using the construct I showed above.