Re: Redirecting standard output to a file

[Michael Hopkins]

On 2008-06-29 17:13:36 +0100, "hns@computer.org" <hns@computer.org> said:

> On 29 Jun., 13:15, Michael Hopkins <michael.hopk...@-rm-this-hopkins-
> research.com> wrote:
> > Hi all
> >
> > I have a question about using the classes in base to redirect standard
> > output to a file without too much hassle or re-writing of code.  I have
> > classes that print themselves to standard output like this:
> >
> >         [ someObject show ];
> >
> > ..but would like to be able to redirect this behaviour within code and
> > possibly in response to user input.  Something like...
> >
> >         [ outputFile appendedWith:[ someObject show ]];
> >
> > I suspect that NSPipe and/or NSFileHandle might be involved but welcome
> > any tips.
> >
> > TIA
> >
> > Michael
> >
> > --
> > ______________________________________________
> >
> >     Hopkins Research      Touch the Future
> > ______________________________________________
>
> Some de-facto standard is that objects derived from NSObject should
> respond to - (NSString *) description which returns a user-readable
> description.
>
> Then, you can write
>
> [[NSFileHandle fileHandleWithStandardOutput] writeData:[[object
> description] dataUsingEncoding:NSUTF8StringEncoding]];
>
> If you prefer to mix OpenSTEP and POSIX:
>
> printf("%s\n", [[object description] UTF8String]);
>
> You could also pack that into a Macro (similar to NSLog which first
> builds a formatted string and then writes to StandardErrlr).
>
> What you also could do in main():
>
> freopen(stdout, "path to file", "w");
>
> -- hns

Thanks for the ideas. Will think about these.

The 'show' method is implemented directly as printf() or uses C 
functions in a separate library that use printf(), so that will not be 
straightforward easy to achieve unless I have misunderstood you, which 
is quite possible as I'm relatively new to the OpenStep API.

Was hoping to use Cocoa/GNUstep goodness to make it a simple task.  Any 
other ideas short of re-implementing the functions to use fprintf() and 
parameterising the file to send to?  Would overriding the 'description' 
method to call [ self show ] achieve this result?

TIA

M

--
______________________________________________

   Hopkins Research      Touch the Future
______________________________________________