Re: [Gnu-arch-users] Pipes?

[Jan Hudec]

On Wed, Mar 17, 2004 at 16:13:01 -0700, Pierce T.Wetter III wrote:
> 
> >For filenames with spaces, this works really well:
> >
> >tla tree-lint -m --unescaped | while read line; do tla delete "$line" 
> >; done
> >
> >This delimits arguments by newline instead of spaces which seems to be
> >your problem, or no?
> 
>  Nope, its more complicated then that. (the above didn't work either)
> 
>  escaping just got added to tla. However, it seems to be a different 
> escaping
> then that used by any of the shells.
> 
>  So if the shell gets involved at any point, bad things happen. Your 
> above example changes the \\ to a \ for instance...

The above example should be fixed by adding -r option to read.

However, it's still incorrect, since it can't read in newline char.

>  Same with xargs.
> 
>  At the end of the day, since tla is doing the escaping, presumably tla 
> will know how
> to undo it as well. So if the shell is kept out of the loop, then it 
> won't have
> any chance of "mucking it up". There is a similar problem with xargs...

Tla does. Actualy the correct way to write the above should be:

tla tree-lint -m | while read -r line; do line=`tla escape --unescaped $line+`; 
tla delete "${line%+}"; done

And even then I am not sure shell won't discard the hard protected space on the 
end!

>  Since tla already outputs lists of files, and already suppresses the 
> annotation of what those files are (i.e. tree-lint and tree-lint -m 
> have different outputs), pipes seem like a simple way around the issue. 
> The other option would be to use a less unique escaping scheme, but 
> that seems like a lot more work.

It's not that much work. It's actualy pretty simple. Just replace it in
one source file in hackerlab.

> Any sort of while loop (and isn't xargs just another case of a while 
> loop?) seems more complicated then a pipe anyways.

No, xargs is an external command. The difference is quite significant.

-------------------------------------------------------------------------------
                                                 Jan 'Bulb' Hudec 
<address@hidden>

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