Re: file:write() fails silently for read-only files

[HyperHacker <hyperhacker@...>]

On Tue, Sep 6, 2011 at 01:14, Sean Conner <sean@conman.org> wrote:
> It was thus said that the Great HyperHacker once stated:
>> On Tue, Sep 6, 2011 at 00:51, Josh Simmons <simmons.44@gmail.com> wrote:
>> > On Tue, Sep 6, 2011 at 4:39 PM, HyperHacker <hyperhacker@gmail.com> wrote:
>> >> Lua 5.1.4  Copyright (C) 1994-2008 Lua.org, PUC-Rio
>> >>> f=io.open('foo.foo', 'r')
>> >>> f:write('ffd')
>> >>> f:close()
>> >>>
>> >>
>> >> Call me crazy, but I feel like f:write() should throw an error when
>> >> trying to write to a read-only file, instead of just doing nothing.
>> >>
>> >> --
>> >> Sent from my toaster.
>> >>
>> >>
>> >
>> > Check the return value of write.
>> >
>> >
>>
>> I get "bad file descriptor" which seems rather misleading. No return
>> value is documented in the manual though.
>
>  Re-read section 5.7:
>
>        Unless otherwise stated, all I/O functions return nil on failure
>        (plus an error message as a second result and a system-dependent
>        error code as a third result) and some value different from nil on
>        success.
>
>  Also, under Unix, the write() system call (which is the system call that
> f:write() eventually calls) can return EBADF (which translates to "bad file
> descriptor") as described in the man page:
>
>        ERRORS
>
>                EBADF fd is not a valid file descriptor or is not open for
>                writing.
>
>                ...
>
>  -spc
>
>
>

Ahh, serves me right for only looking at the specific function and not
the section header.

Just because Unix does it that way though doesn't necessarily mean
it's the best way. I think throwing an error makes more sense than
returning a system-dependent, odd-sounding error code/message.

-- 
Sent from my toaster.