TLDR
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Harvard CS 61 (2017) lecture notes covering Unix pipe internals, SIGPIPE behavior, zombie processes, and a pipe-based waitpid alternative.
Key Takeaways
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McIlroy proposed pipes in 1964; his 6-line shell solution to Knuth’s text-parsing problem illustrates pipes over algorithmic complexity.
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SIGPIPE kills a writer when no readers remain – this is why
seq stops running when piped to less and the screen fills.
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Pipes can substitute for
waitpid: close the write end in the parent, then read blocks until the child exits and all write ends close.
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Zombie processes accumulate when a parent never calls
waitpid; manyfork without root hits ~3400 forks, with root ~6890, before OS limits cut it off.
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Orphaned children are reparented to
init (pid 1), which calls waitpid to reclaim their process structures.
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