One posting is enough, really.
There is no guaranteed or specified parent child relationship between the processes in a pipeline. This means that you cannot predict which process's status will be the one returned as that of the pipeline as a whole.
You can force this in your contrived example by adding an exit call.
All of these will print "true:"
(true | true; exit 0) && echo true || echo false
(false | true; exit 0) && echo true || echo false
(true | false; exit 0) && echo true || echo false
(false | false; exit 0) && echo true || echo false
Randall Schulz
At 14:09 2003-01-12, Rolf Campbell wrote:
/home/rcampbell> (true | true) && echo true || echo false true /home/rcampbell> (true | false) && echo true || echo false false /home/rcampbell> (false | true) && echo true || echo false true /home/rcampbell> (false | false) && echo true || echo false falseThe third test above yields different results when run on Linux. I'm wondering if this was the desired result or not? (This is not a new problem, it's been around for at least a year of releases). It makes some makefiles not work as expected, specifically, the GCC manual describes how to perform auto-dependency analysis like: gcc ... | sed ... But, if gcc fails, sed will still work, thus make will not consider it a failure and will continue. I know there are many ways to avoid this specific problem, already implemented one. Just wanted to let you guys know. -Rolf Campbell
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