On 13Sep2016 14:27, bruce <badoug...@gmail.com> wrote:
I'm doing 100s/1000s of these..
Still a smallish number.
but.. the othe parts of th operation are
longer/more compute expensive.. this is essentially noise in the scheme of
things.. and i'm fairly certain the resource usage is a wash as well for
the diff approaches
If you have speed issues, one thing to keep in mind is that with the shell,
fork/exec will often outweigh any compute cost in a regexp.
The core deal with interpreted languages (shell, perl, python etc) is that you
should try to minimise the cost of the interpretation. So the classic shell
example looks like this:
# expensive, fires off separate commands per file
for f in *.txt
do
cat "$f" | awk | sed | ...
done
vs:
for f in *.txt
do
file-specific-awk ...
done | generic-sed | ...
i.e. a theoretical example where you can run a whole bunch of things though a
single sed or whataver outside the loop. Obvious very dependent on your exact
problem, but I hope the approach is evident.
There are flipsides to this of course; if the code becomes unreadable or
unmaintainable then the programmer cost can exceed the actual real world
runtime benefit, particularly for once-off tasks.
Re the unreadable bit, that is one of my rules of thumb for switching
languages: when the task is no longer clearly and succinctly expressed.
Cheers,
Cameron Simpson <c...@zip.com.au>
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