/usr/share/doc/ruby-lockfile/examples/lock.sh is in ruby-lockfile 2.1.0-4.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 | #!/bin/sh
export RUBYLIB="../lib:./lib"
export PATH="../bin:./bin:$PATH"
#export LOCKFILE_DEBUG=1
(r=`ruby -e 'p(rand(2))'`; sleep $r; rlock ./lockfile 'sleep 1; printf "\n$$ aquired lock @ `date`\n\n"') &
(r=`ruby -e 'p(rand(2))'`; sleep $r; rlock ./lockfile 'sleep 1; printf "\n$$ aquired lock @ `date`\n\n"') &
(r=`ruby -e 'p(rand(2))'`; sleep $r; rlock ./lockfile 'sleep 1; printf "\n$$ aquired lock @ `date`\n\n"') &
wait
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