59 lines
1.7 KiB
Perl
59 lines
1.7 KiB
Perl
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Specification of the concurrency action:
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$ cat > dune-project << EOF
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> (lang dune 3.7)
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> EOF
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$ cat > dune << EOF
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> (rule
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> (action
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> (concurrent )))
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> EOF
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$ dune build
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File "dune", line 3, characters 2-15:
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3 | (concurrent )))
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^^^^^^^^^^^^^
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Error: 'concurrent' is only available since version 3.8 of the dune language.
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Please update your dune-project file to have (lang dune 3.8).
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[1]
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Requires Dune 3.8.
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$ cat > dune-project << EOF
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> (lang dune 3.8)
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> EOF
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(concurrent ...) runs actions concurrently. Here we mock up an example where two
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subactions rely on eachother to also be running in order to terminate.
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We write a shell script that will simultaneously read and write to two named
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pipes. (This has to be similtaneious otherwise the read will block the write).
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They will block on the read however, which means if called with the same two
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pipes but swapped, they will only terminate when both scripts are running at the
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same time.
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$ cat > run.sh << EOF
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> echo foo>\$1 & read line<\$2
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> EOF
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We create an action that will create named pipes a and b and then run our script
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on both of them, but importantly inside the concurrent action. This will
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demonstrate that subactions are indeed being run concurrently.
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$ cat > dune << EOF
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> (rule
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> (deps run.sh)
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> (alias my-rule)
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> (action
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> (progn
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> (run mkfifo a b)
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> (concurrent
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> (run sh run.sh a b)
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> (run sh run.sh b a)))))
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> EOF
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When we run the rule, we see that the two actions are indeed run concurrently.
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$ dune build -j2 @my-rule --force
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Notice the need for a -j2. If Dune was configured with -j1 then the action would
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never terminate.
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