Re: Sed and redirection into the same file

Thanks guys....perl to the rescue :)

Josh.


On 9/29/06, Brendon Oliver <[email protected]> wrote:
> On Friday 29 September 2006 15:53, Joshua Bassett wrote:
>
> > It all appears to work fine, but the problem is when redirecting the
> > output back into the same file...I end up with empty files! For
> > example, the following works fine:
> >
> > for x in `grep -lr 'foo' app | grep -v "svn"`; do sed 's/foo/bar/'
> > <${x} >${x}.new; done
> >
> > Clearly it's something to do with the <${x} >${x} part. What am I missing
> > here?
>
> You can't do in-place file edits with sed.  Stick with what you found to work
> and just rename the .new file if it's non-zero in size otherwise delete it.
> e.g:
>
> for x in `grep -lr 'foo' app | grep -v "svn"`
> do
> sed 's/foo/bar/'<${x} >${x}.new
> if [ -s ${x}.new ]; then
>    mv ${x}.new ${x}
> else
>     rm -f ${x}.new
> fi
> done
>
>
> otherwise, use a perl one-liner (eg. perl -pie 's/foo/bar/').  Perl's -i
> switch will do in-place file edits for you.
>
> Cheers,
>
> - brendon.
>
> --
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>                 -- Robert Louis Stevenson
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