wait gets confused when second argument exits before first (i think)

wait gets confused when second argument exits before first (i think)

[Mikael Magnusson]

zsh -f
localhost% sleep 2 & a=$\! ; sleep 1 & wait $a $\!
[1] 31989
[2] 31990
[2]  + done       sleep 1
[1]  + done       sleep 2
wait: pid 31990 is not a child of this shell
localhost% sleep 2 & a=$\! ; sleep 1 & wait $\! $a
[1] 32121
[2] 32122
[2]  + done       sleep 1
[1]  + done       sleep 2
localhost% sleep 1 & a=$\! ; sleep 2 & wait $\! $a
[1] 32125
[2] 32126
[1]  - done       sleep 1
[2]  + done       sleep 2
wait: pid 32125 is not a child of this shell

localhost% sleep 2 & sleep 1 & wait %1 %2
[1] 31993
[2] 31994
[2]  + done       sleep 1
[1]  + done       sleep 2
wait: %2: no such job
localhost% sleep 2 & sleep 1 & wait %2 %1
[1] 31997
[2] 31998
[2]  - done       sleep 1
[1]  + done       sleep 2
localhost% sleep 1 & sleep 2 & wait %2 %1
[1] 32001
[2] 32002
[1]  + done       sleep 1
[2]  + done       sleep 2
wait: %1: no such job

So it looks like it doesn't matter if %1 or %2 exits first, just which
is the first argument to wait.
Same happens both on current cvs and on 4.3.6.

-- 
Mikael Magnusson

Re: wait gets confused when second argument exits before first (i think)

[Bart Schaefer]

On Apr 10,  3:37am, Mikael Magnusson wrote:
}
} So it looks like it doesn't matter if %1 or %2 exits first, just which
} is the first argument to wait.

The wait isn't performed in parallel for all the argument PIDs at once
(it's not like doing a select() on a list of file descriptors).  Rather
the shell waits for each PID in the order it appears on the command
line, before attempting to wait on the next one.

See zsh-workers/27442 and its thread for possibly-related discussion;
there doesn't appear to be a requirement that the shell keep track of
more than one already-exited asynchronous job.

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