# Trouble with open/write/close cycle **URL:** \ **Category:** Ruby\ **Created:** [March 24, 2006, 5:42pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855 "2006-03-24T17:42:51Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 5:42pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/1 "2006-03-24T17:42:51Z")
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: 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 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: puma:~\> od -h junk 0000000 0000 0000 0000 0000 0000 0000 0000 0000 \* 0000120 0000 0000 0000 0000 0000 3130 3332 3534 0000140 3736 0a38 0000144 puma:~\> Anyone know what I’m doing wrong? I tried using sysseek and syswrite, but I got the same results. Is Ruby’s internal buffering screwing me up here somehow? TIA. – Toby DiPasquale ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 5:45pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/2 "2006-03-24T17:45:51Z")
From above: - f = File.open ‘crapper’, ‘w’ - f = File.open ‘junk’, ‘w’ Sorry. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 5:57pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/3 "2006-03-24T17:57:53Z")
On 24-Mar-06, at 11:43 AM, Toby DiPasquale wrote: > len = 0 > end > 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 S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [http://www.stok.ca/~mike/](http://www.stok.ca/~mike/) The “`Stok’ disclaimers” apply. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 5:58pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/4 "2006-03-24T17:58:55Z")
> len = File.stat( 'junk').size f = File.open 'crapper', 'w' Are there really 2 files? or is this a typo? The docs on IO::open says tha using the ‘w’ mode cause the file to be truncated if it exists. You need to look at ‘a’ mode cheers ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 6:02pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/5 "2006-03-24T18:02:00Z")
On Mar 24, 2006, at 10:43 AM, Toby DiPasquale wrote: > begin > len = File.stat( ‘junk’).size > rescue > len = 0 > end > puts len.to\_s > f = File.open ‘crapper’, ‘w’ > f.seek len The above procedure seems like a complex way to do: File.open(“junk”, “a”)… Will that work for you? James Edward G. II ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 6:02pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/6 "2006-03-24T18:02:24Z")
Mike S. wrote: > opening a file for writing truncates it. ARRRGH! I’m a moron. Of course, you are right. Thanks for the mental clue-by-four. – Toby DiPasquale ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 6:03pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/7 "2006-03-24T18:03:35Z")
James G. wrote: > The above procedure seems like a complex way to do: > > File.open(“junk”, “a”)… > > Will that work for you? No, the above code was just a small example to illustrate the issue. The real code does lots more before and after each write. – Toby DiPasquale ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 24, 2006, 6:09pm UTC](https://www.ruby-forum.com/t/trouble-with-open-write-close-cycle/86855/8 "2006-03-24T18:09:48Z")
Toby DiPasquale wrote: > From above: > > - f = File.open ‘crapper’, ‘w’ > > - f = File.open ‘junk’, ‘w’ > > Sorry. Not a problem. When I run your snippet i get: > ruby -w fwrite-test.rb > 0 > 11 > 22 > 33 > 44 > 55 > 66 > 77 > 88 > 99 It looks like seeking on an empty file fills it with null data. Not sure if thats a Ruby thing or a feature of the underlying IO libs. change the ‘w’ to an ‘a’ (an delete the current ‘junk’ file) and the file produced looks like: 012345678 012345678 012345678 012345678 012345678 012345678 012345678 012345678 012345678 012345678 cheers