[erlang-questions] Read and delete file

Jayson Vantuyl <>
Tue Dec 15 07:15:12 CET 2009


Do you have control over the file?  Can you rotate between files automatically?  This is easy.  Deleting lines from the beginning of the file requires rewriting the whole file.  It's just the way that files are.  Sorry.

On Dec 14, 2009, at 10:06 PM, maruthavanan s wrote:

> Hi,
> 
> My requirement is quite simple,
> 
> I have a large file which contains numbers and I shall take those numbers process the numbers and delete the processsed numbers. There are was where I can pause this process at certain conditions and resume when user instructs me to do so.
> 
> Regards,
> Marutha
> 
> > From: 
> > Date: Sat, 12 Dec 2009 02:40:37 -0800
> > CC: ; 
> > To: 
> > Subject: Re: [erlang-questions] Read and delete file
> > 
> > Under Unix, there is no good way to delete a line from the front of a file. You can truncate the file (shorten it, cutting lines off at the end), but not from the front.
> > 
> > If you're willing to do it all on disk (possibly with multiple copies of the data), it can be done, but it's hard to make a recommendation without knowing exactly what you're doing.
> > 
> > On Dec 12, 2009, at 2:18 AM, maruthavanan s wrote:
> > 
> > > 
> > > Hi,
> > > 
> > > The file is huge so I cannot take and keep it in memory.
> > > 
> > > Regards,
> > > Marutha
> > > 
> > >> To: 
> > >> From: 
> > >> CC: 
> > >> Date: Fri, 11 Dec 2009 15:44:52 +0100
> > >> Subject: Re: [erlang-questions] Read and delete file
> > >> 
> > >> Greetings,
> > >> 
> > >> The simplest way, if you can have the whole file in memory, would be to
> > >> read all lines, handle a single line and then write all the remaining
> > >> lines out to the file. Then repeat.
> > >> Use file:read_file/1 (split the line from the binary) and
> > >> file:write_file/2.
> > >> 
> > >> 
> > >> bengt
> > >> 
> > >> On Fri, 2009-12-11 at 08:50 -0500, maruthavanan s wrote:
> > >>> Hi,
> > >>> 
> > >>> I am opening a file using file and I read the file line by line using io:get_line.
> > >>> But after reading this line I need to delete the read line from the file.
> > >>> 
> > >>> Appreciate you help.
> > >>> 
> > >>> Thanks,
> > >>> Marutha
> > >>> 
> > >> 
> > >> 
> > >> ________________________________________________________________
> > >> erlang-questions mailing list. See http://www.erlang.org/faq.html
> > >> erlang-questions (at) erlang.org
> > >> 
> > > 
> > 
> > 
> > ________________________________________________________________
> > erlang-questions mailing list. See http://www.erlang.org/faq.html
> > erlang-questions (at) erlang.org
> > 



-- 
Jayson Vantuyl








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