While not loop in ruby

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October 2nd, 2007, 05:35 AM

karym6

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While not loop in ruby

Hi All,

I am trying to write a while not loop in Ruby, I have taken a look at all the docs etc on control structures but cant quite nail this one...

Basically, I want to do something like this:

Code:

while Dir.entries("c:\\preprocess") != "." or ".."{
Dir.foreach("c:\\preprocess") {|sitename|system("c:\\releasescripts\\aspincluder.exe c:\\preprocess #{sitename}")} 
} end

But I keep getting:

DOS Code:

Original - DOS Code
C:/dir_test.rb:34: syntax error, unexpected '{', expecting kDO_COND or ':' or '\ n' or ';' C:/dir_test.rb:36: syntax error, unexpected '}', expecting $end } end ^

C:/dir_test.rb:34: syntax error, unexpected '{', expecting kDO_COND or ':' or '\
n' or ';'
C:/dir_test.rb:36: syntax error, unexpected '}', expecting $end
} end
 ^

Can someone point out my error? I need the Dir.foreach to do something while the directory isnt "." or ".."

Cheers
-
Karym6

October 2nd, 2007, 07:00 AM

L7Sqr

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Quote:

while Dir.entries("c:\\preprocess") != "." or ".."

So you are aware, the logic of this statement is wrong, so the intended control is not actually what you would get.
When you say:

Code:

while cond1 or cond2

You are saying that either cond1 or cond2 evaluating to non nil/false will allow the loop to happen. So in your specific statement, you are saying

Code:

while X or ".."

where X could be anything as ".." will always allow the loop to be entered.
For example:

Code:

while ".." do
   puts "Still looping!"
end

will produce

Code:

Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
Still looping!
...

To answer your question directly, you could change the loop construct to use an iterator and only use items that qualify...

Code:

Dir.entries("c:\\preprocess").each do |entry|
   next if entry =~ /^\./
   # now any filename that begins with a '.' will not reach this line
end

That will eliminate 'hidden' files as well as simply '..' and '.', so you may have to adjust the reg ex to match against to suit your needs.

__________________
-- I'll provide you with reference points; if they dont work, refer to something else.

If you process text, this might make your life a little easier.

October 2nd, 2007, 07:14 AM

karym6

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Thanks for the reply L7Sqr!

does this mean then, if I wished to exclude further directories that did not start with a "." I could use:

Code:

Dir.entries("c:\\preprocess").each do |entry|
   next if entry =~ /^\./ or "some_dir"
end

Or have I totally lost track?

Cheers
-
K

October 2nd, 2007, 07:31 AM

[H4z3]

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Code:

next if entry =~ /^\./ or entry =~ /\.txt$/

Will skip files beginning with a dot and ending in .txt, don't forget that the entry variable is each file name

Last edited by [H4z3] : October 2nd, 2007 at 07:37 AM.

October 2nd, 2007, 08:05 AM

karym6

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Quote:

Originally Posted by [H4z3]

Code:

next if entry =~ /^\./ or entry =~ /\.txt$/

Will skip files beginning with a dot and ending in .txt, don't forget that the entry variable is each file name

ahh, I think I see now.

So in order to ignore a whole directory as opposed to a file i can do:

Code:

next if entry =~ /^\./ or entry =~ /\some_dir$/

cheers
-
K

October 2nd, 2007, 08:31 AM

L7Sqr

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Quote:

So in order to ignore a whole directory as opposed to a file i can do:

The result of Dir.entries will be an array of strings. So there is no idea of file/directory at that point.
If you have a list of items you would like to exclude, there is an easier method that you may be interested in.

Code:

# items to ignore
ignored = ['.', '..', 'some_dir']
(Dir.entries("c:\\preprocess") - ignored).each do |entry|
   # no items in ignored list will be present here
end

[edit]
Also, if you are looking to only process files (and ignore all directories) then you can use test

Code:

Dir.entries("c:\\preprocess").each do |entry|
   next unless test ?f, entry
   # or, next if test ?d, entry
   # depends on what you want to limit
end

[/edit]

Comments on this post

karym6 agrees: very helpful

Last edited by L7Sqr : October 2nd, 2007 at 08:35 AM.

October 2nd, 2007, 08:39 AM

karym6

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Quote:

Originally Posted by L7Sqr

Code:

# items to ignore
ignored = ['.', '..', 'some_dir']
(Dir.entries("c:\\preprocess") - ignored).each do |entry|
   # no items in ignored list will be present here
end

[edit]
Also, if you are looking to only process files (and ignore all directories) then you can use test

Code:

Dir.entries("c:\\preprocess").each do |entry|
   next unless test ?f, entry
   # or, next if test ?d, entry
   # depends on what you want to limit
end

[/edit]

thanks very much L7Sqr this is what I didnt get from the docs etc

October 2nd, 2007, 09:49 AM

karym6

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Quote:

Originally Posted by karym6

thanks very much L7Sqr this is what I didnt get from the docs etc

one last question - would I be able to include specific directories with this code?

Code:

# items to ignore
ignored = ['.', '..', 'some_dir']
(Dir.entries("c:\\preprocess") - ignored).each do |entry|
   # no items in ignored list will be present here
end

is the - ignored the key part here?

Cheers
-
Karim

October 2nd, 2007, 09:03 PM

L7Sqr

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Yes. As I mentioned, the 'entries' method returns an array of strings.
You are free to add (+) and remove (-) from as you see fit.
As an example of adding and removing from an array:

Code:

a = ['a', 'b', 'c', 'd', 'e']
b = ['d', 'e', 'f', 'g', 'h']
a - b # produces ['a', 'b', 'c']
a + b # produces ['a', 'b', 'c', 'd', 'e', 'd', 'e', 'f', 'g', 'h']

Notice the duplicates in teh second result.

#10

October 3rd, 2007, 07:36 AM

karym6

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Quote:

Originally Posted by L7Sqr

Yes. As I mentioned, the 'entries' method returns an array of strings.
You are free to add (+) and remove (-) from as you see fit.
As an example of adding and removing from an array:

Code:

a = ['a', 'b', 'c', 'd', 'e']
b = ['d', 'e', 'f', 'g', 'h']
a - b # produces ['a', 'b', 'c']
a + b # produces ['a', 'b', 'c', 'd', 'e', 'd', 'e', 'f', 'g', 'h']

Notice the duplicates in teh second result.

Excellent! Thankyou very much for your help so far

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