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More clarification about parallel job launch and wait

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Remzi Arpaci-Dusseau
2018-02-08 11:19:07 -06:00
parent 363d89d53d
commit b89cd85705
1 changed files with 6 additions and 4 deletions
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processes-shell/README.md
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@@ -181,11 +181,13 @@ wish> cmd1 & cmd2 args1 args2 & cmd3 args1
In this case, instead of running `cmd1` and then waiting for it to finish,
your shell should run `cmd1`, `cmd2`, and `cmd3` (each with whatever arguments
the user has passed to it).
the user has passed to it) in parallel, *before* waiting for any of them to
complete.
**Important:** For any new processes your shell creates via `fork()`, you must
make sure to use `wait()` (or `waitpid`) to wait for them to complete. Not
doing so is a bug.
Then, after starting all such processes, you must make sure to use `wait()`
(or `waitpid`) to wait for them to complete. After all processes are done,
return control to the user as usual (or, if in batch mode, move on to the next
line).
### Program Errors