From: Mike Stok <mike@...>
Date: 2006-03-25T01:57:47+09:00
Subject: Re: Trouble with open/write/close cycle


On 24-Mar-06, at 11:43 AM, Toby DiPasquale wrote:

> Hi all,
>
> I'm having trouble getting an open/write/close cycle to actually  
> put the
> correct data in the file. Here's some code that illustrates the  
> problem:
>
> <snip>
> x = "012345678\n"
> 10.times do
>   len = 0
>   begin
>     len = File.stat( 'junk').size
>   rescue
>     len = 0
>   end
>   puts len.to_s
>   f = File.open 'crapper', 'w'
>   f.seek len
>   f.write x
>   f.close
> end
> </snip>
>
> produces:
>
> 0
> 10
> 20
> 30
> 40
> 50
> 60
> 70
> 80
> 90
>
> as output. However, the file 'junk' is filled with zeroes, except for
> the last 10 bytes, which are what you'd expect them to be:

opening a file for writing truncates it.  Does this, opening it for  
reading & writing, do what you want?

x = "012345678\n"
10.times do
   len = 0
   begin
     len = File.stat( 'junk').size
   rescue
     len = 0
   end
   puts len.to_s
   f = File.open 'junk',File::RDWR|File::CREAT
   f.seek len
   f.write x
   f.close
end

Mike

-- 

Mike Stok <mike@stok.ca>
http://www.stok.ca/~mike/

The "`Stok' disclaimers" apply.