Issue
I tried to run a one-off dyno and fetch the exit code. However, the Heroku CLI command heroku run --exit-code failed with a message like
FATA exec: "command;": executable file not found in $PATH
▸ No exit code returned
Resolution
Create a script file like below and specify it as the ENTRYPOINT in the Dockerfile:
#!/usr/bin/env ruby
HEROKU_EXIT_STATUS_ARG = "\uFFFF heroku-command-exit-status: $?"
HEROKU_EXIT_STATUS_CMD = "; echo \"#{HEROKU_EXIT_STATUS_ARG}\""
argv = ARGV.dup
heroku_exit_status = case
when argv.size > 2 && argv[-3].end_with?(';') && argv[-2] == 'echo' && argv[-1] == HEROKU_EXIT_STATUS_ARG
argv.pop # HEROKU_EXIT_STATUS_ARG
argv.pop # "echo"
argv[-1] = argv[-1].slice(0...-1) # trailing semicolon
true
when argv.any? && argv[-1].end_with?(HEROKU_EXIT_STATUS_CMD)
argv[-1] = argv[-1].slice(0...-HEROKU_EXIT_STATUS_CMD.size)
true
else
false
end
if heroku_exit_status
system(*argv)
puts HEROKU_EXIT_STATUS_ARG.sub('$?', $?.exitstatus.to_s)
exit! $?.exitstatus
else
exec(*argv)
end
The Heroku CLI command fails because of the mismatch in how the Heroku CLI command constructs a sequence of commands to be executed and sends the exit status back and in how the platform interprets the command to be executed on the one-off dyno. The script works around the mismatch.