Unix tools: sponge
Joey
writes
about the lack of new tools that fit into the Unix philosophy. My favourite
of such things I’ve written is
sponge. It addresses the
problem of editing files in-place with Unix tools, namely that if you just
redirect output to the file you’re trying to edit then the redirection takes
effect (clobbering the contents of the file) before the first command in the
pipeline gets round to reading from the file. Switches like sed -i and
perl -i work around this, but not every command you might want to use in a
pipeline has such an option, and you can’t use that approach with
multiple-command pipelines anyway.
I normally use sponge a bit like this:
sed '...' file | grep '...' | sponge file
Since it’s so trivial I imagine lots of other people have written something similar (another common name for it seems to be inplace; my name indicates soaking up all the input and then squeezing it all out again); but I do keep meaning to try to get a rewritten version into coreutils at some point.