Closing files with abrupt interruptions

ruby-talk
1

loop do
  File.open somefile, 'r' do |io|
    next
  end
end

Does somefile get closed?
How would I test that?
I have the same question if it raises an error (that gets rescued) or
throws a symbol.

Daniel Brumbaugh Keeney

2

Daniel Brumbaugh Keeney wrote:

loop do
  File.open somefile, 'r' do |io|
    next
  end
end

Does somefile get closed?
How would I test that?
I have the same question if it raises an error (that gets rescued) or
throws a symbol.

Daniel Brumbaugh Keeney

There are two ways to open a file for reading in ruby, the first is:

f = File.open("fred.txt", "r")
  f.each do |l|
    puts l
  end
f.close

in the above case you have to explicitly close the file, however with this:

File.open("fred.txt","r") do |f|
  f.each do |l|
    puts l
  end
end

The opened file is referenced by the variable f, however f is in the scope of the 'File.open() do ... end' and once the program goes past the closing 'end' the f will be removed. The deletion of the file handle triggers the close. So no need for an explicit close.

The second way is also more 'rubyish'.

3

loop do
  File.open somefile, 'r' do |io|
    next
  end
end

Does somefile get closed?

Yes. See also Peter's explanation.

How would I test that?

Easily:

robert@fussel ~
$ echo 1 > x

irb(main):001:0> io = nil
=> nil
irb(main):002:0> File.open("x") {|io| p io, io.closed?}
#<File:x>
false
=> nil
irb(main):003:0> p io, io.closed?
#<File:x (closed)>
true
=> nil

I have the same question if it raises an error (that gets rescued) or
throws a symbol.

irb(main):004:0> File.open("x") {|io| p io, io.closed?; raise "E"}
#<File:x>
false
RuntimeError: E
         from (irb):4
         from (irb):4:in `open'
         from (irb):4
irb(main):005:0> p io, io.closed?
#<File:x (closed)>
true
=> nil

Cheers

  robert

···

On 15.02.2008 14:39, Daniel Brumbaugh Keeney wrote:
         from :0