On 24May2020 19:28, David Mertz <[email protected]> wrote:
On Sun, May 24, 2020 at 6:56 PM Steven D'Aprano <[email protected]> wrote:
> I use bash a lot, and writing something like this is common:
> cat data | sort | cut -d; -f6 | grep ^foo | sort -r | uniq -c
And today's "Useless Use Of cat Award" goes to... :-)
sort data | ...
(What is it specifically about cat that is so attractive? I almost
certainly would have done exactly what you did, even knowing that sort
will take a file argument.)
This is probably going afield since it is a bash thing, not a Python
thing. But I can actually answer this quite specifically.
When I write a pipeline like that, I usually do not do it in one pass. I
write a couple of the stages, look at what I have, and then add some more
stages until I get it right. Many of the commands in the pipeline can take
a file argument (not just sort, also cut, also grep, also uniq...
everything I used in the example).
People forget that redirections may appear anywhere rather than just at
the end of the command:
<data sort | cut | ... >output
But I take your point on incremental build-the-pipeline, I do that a
lot.
Cheers,
Cameron Simpson <[email protected]>
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