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- Subject: Re: Question about io.open modes
- From: Rena <hyperhacker@...>
- Date: Wed, 21 Mar 2012 00:27:11 -0600
On Wed, Mar 21, 2012 at 00:18, Dirk Laurie <dirk.laurie@gmail.com> wrote:
>>>> I can't quite understand what some of the modes do for io.open as explained
>>>> in 5.1 manual. Specifically, I'm not sure what "r+", "w+", and "a+" modes
>>>> do.
>>
>> Even the manual (for 5.1 at least) says: This string is exactly what
>> is used in the standard C function fopen.
>>
>
> Which means:
>
> r Open text file for reading. The stream is positioned at the
> beginning of the file.
>
> r+ Open for reading and writing. The stream is positioned at the
> beginning of the file.
>
> w Truncate file to zero length or create text file for writing.
> The stream is positioned at the beginning of the file.
>
> w+ Open for reading and writing. The file is created if it does
> not exist, otherwise it is truncated. The stream is positioned
> at the beginning of the file.
>
> a Open for appending (writing at end of file). The file is cre‐
> ated if it does not exist. The stream is positioned at the end
> of the file.
>
> a+ Open for reading and appending (writing at end of file). The
> file is created if it does not exist. The initial file position
> for reading is at the beginning of the file, but output is
> always appended to the end of the file.
>
I wonder why the 5.2 manual doesn't say it's the same as fopen,
though. Did they change/add some modes, or did they just not want to
have to guarantee fopen's behaviour? Or is it a simple omission?
--
Sent from my toaster.