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

[Gé Weijers <ge@...>]

You can use 'assert' in many cases:

f = assert(io.open('foo.foo', 'r'))
assert(f:write("xyzzy"))
assert(f:close())

Gé


On Tue, 6 Sep 2011, Dirk Laurie wrote:

> On Tue, Sep 06, 2011 at 08:39:00AM +0200, HyperHacker 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.
>
> There are two ways of handling errors: testable return values, and
> throwing errors.  Among programming languages that I use, Lua is unique
> in giving you a seamless way of overriding whatever default choice it
> has made.  So you can do this:
>
> local io_write = io.write
> io.write = function(...)
>    local test, message, code = io_write(...)
>    if test==nil then error(message,2) end
>    end
>
> If io.write had thrown an error instead, you could similarly have
> overridden it by a wrapper that uses pcall.
>
> Dirk