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Comment by yjftsjthsd-h | Hacker News Reader

Why

  (; flock -n 9

and not

  ( flock -n 9

?

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It's a "for" loop.

Could you elaborate?

A for loop in a shell script may sometimes look like this:

`for ((i = 0 ; i < max ; i++ )); do echo "$i"; done`

Here this is essentially a "while" loop, meaning it will keep executing the commands as long as we don't reach `exit 1`.

(; flock -n 9 || exit 1; # ... commands executed under lock ...; )

It doesn't seem to work?

  [~] 0 $ ( flock -n 9 || exit 1; echo in loop ; sleep 3 ; echo done working ; ) 9>~/tmp/mylock
  in loop
  done working
  [~] 0 $ (; flock -n 9 || exit 1; echo in loop ; sleep 3 ; echo done working ; ) 9>~/tmp/mylock
  -bash: syntax error near unexpected token `;'
  [~] 2 $

(This is bash)

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