End of file error when trying to Marshal.load

[Vahagn Hayrapetyan]

Hi,-

I am trying out the marshaling functionality of Ruby with this
documentation as a guide:

http://www.ruby-doc.org/core/classes/Marshal.html

Code goes like this:

*****************************

class Klass
def initialize(str)
@str = str
end
def sayHello
@str
end
end

def marshalKlass
o = Klass.new("hello\n")
print o.sayHello
Marshal.dump(o, File.open("output.txt", "w"))
data = File.open("output.txt") # all fine up until here
obj = Marshal.load(data) # EOFError
print obj.sayHello
end

if __FILE__ == $PROGRAM_NAME
marshalKlass
end

*****************************

The line:
obj = Marshal.load(data)
gives the following error:

Klass.rb:19:in `load': end of file reached (EOFError)
from Klass.rb:19:in `marshalKlass'
from Klass.rb:32

The line:
data = File.open("output.txt") places the cursor at the start of the
file. What's wrong?

Thanks!

/ Vahagn

 

[Tim Hunter]

The line:
obj = Marshal.load(data)
gives the following error:

Klass.rb:19:in `load': end of file reached (EOFError)
from Klass.rb:19:in `marshalKlass'
from Klass.rb:32

The line:
data = File.open("output.txt") places the cursor at the start of the
file. What's wrong?

I'm guessing you're on Windows. You need to open the file in binary
mode. That is, with "wb" and "rb".

 

[Vahagn Hayrapetyan]

Tim, I'm on Mac OS X (Leopard). Now I have:

Marshal.dump(o, File.open("output.txt", "wb"))
data = File.open("output.txt", "rb")
obj = Marshal.load(data)

But I get the exact same error.

/ Vahagn

 

[Robert Klemme]

Please do not top post.

Tim, I'm on Mac OS X (Leopard). Now I have:

Marshal.dump(o, File.open("output.txt", "wb"))
data = File.open("output.txt", "rb")
obj = Marshal.load(data)

But I get the exact same error.

/ Vahagn

You also need to make sure you write the complete file which you don't
because you're not closing the File properly.

http://blog.rubybestpractices.com/posts/rklemme/001-Using_blocks_for_Robustness.html

Cheers

robert

 

[Vahagn Hayrapetyan]

@Robert:

Ah! "While not closing a read only file usually does not have dramatic
consequences, not closing a file opened for writing likely has dramatic
consequences."

The working method:

def marshalKlass
o = Klass.new("hello\n")
print o.sayHello
dumped = File.open("output.txt", "w")
Marshal.dump(o, dumped)
dumped.close
data = File.open("output.txt", "r")
obj = Marshal.load(data)
data.close
print obj.sayHello
end


Thanks,
/ Vahagn

 

[Robert Klemme]

@Robert:

Ah! "While not closing a read only file usually does not have dramatic
consequences, not closing a file opened for writing likely has dramatic
consequences."

The working method:

def marshalKlass
o = Klass.new("hello\n")
print o.sayHello
dumped = File.open("output.txt", "w")
Marshal.dump(o, dumped)
dumped.close
data = File.open("output.txt", "r")
obj = Marshal.load(data)
data.close
print obj.sayHello
end

This is better but my point in the blog article was a different one:
use the block form of File.open because it is more robust.

Cheers

robert

 

[Vahagn Hayrapetyan]

@Robert: Sure!

def marshal_class
o = Klass.new("hello")
print o.sayHello, " from original object\n"
File.open("data.txt", "w") do |file|
Marshal.dump(o, file)
end
File.open("data.txt", "r") do |file|
@obj = Marshal.load(file)
end
print @obj.sayHello + " from restored object\n"
end

That's a good article, btw.
Cheers,
Vahagn