Proper syntax


 
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# 1  
Old 07-19-2012
Proper syntax

I'm new to Unix, and just had a quick question.

I'm writing a bash script, and I was wondering what proper programming etiquette was for piping. How many pipes is too many pipes?
Code:
OLDEST=$(find . -maxdepth 1 -type d -newermt 2012-07-01 ! -newermt
2012-07-30 | xargs ls -1td | tail -2)

echo "${OLDEST}\n"

My next step would be to tar those directories, then move them. I'm not asking if it's a matter of CAN I pipe it all, but SHOULD I pipe it all. As its proper to indent while in a loop, is there a unanimous rule for amount of pipes?

Thanks
# 2  
Old 07-19-2012
With a long series of pipes it can be hard to trap and respond correctly to an error.
More pipes makes that harder to. Learn about the PIPESTATUS array if you want to write solid bash and use lots of pipes.

Some operations require pipes to become more efficient, e.g., pipes "cost" less disk space. And leave behind no intermediate files.

The book 'Code Complete' recommends that a line of code be split with continuation "\" when it gets beyond the max line length on your screen: ~80 character positions, including leading tabs and spaces. You can also split on a pipe symbol. This is to provide readability for the next guy.
 
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