Hudson : “yes: standard output: Broken pipe”

Question

I need to run a shell script in hudson. That script needs an answer from the user. To give an automatic answer I did the following command line :  

yes         


        

Answer 1

Since yes and ./MyScript.sh can each be run in an explicit subshell, it is possible to background the yes command, send yespid to the ./MyScript.sh subshell and then implement a trap on EXIT there to manually terminate the yes command. (The trap on EXIT should always be implemented in the subshell of the last command of a piped commmand sequence).

# avoid hangup or "broken pipe" error message when parent process set SIGPIPE to be ignored
# sleep 0 or cat /dev/null: do nothing but with external command (for a shell builtin command see: help :)
(
trap "" PIPE
( (sleep 0; exec yes) & echo ${!}; wait ${!} ) | 
   ( 
     trap 'trap - EXIT; kill "$yespid"; exit 0' EXIT
     yespid="$(head -n 1)"
     head -n 10  # replacement for ./MyScript.sh
   )
echo ${PIPESTATUS[*]}
)

If you want to exit the yes subshell with exit code 0 you can do this as well:

# avoid hangup or "broken pipe" error message when parent process set SIGPIPE to be ignored
# set exit code of yes subshell to 0
(
trap "" PIPE
   (
      trap 'trap - TERM; echo "kill from yes subshell ..." 1>&2; kill "${!}"; exit 0' TERM 
      subshell_pid="$(bash -c 'echo "$PPID"')"
      (sleep 0; exec yes) & echo "${subshell_pid}"; wait ${!} 
   ) | 
   ( 
      trap 'trap - EXIT; kill -s TERM "$subshell_pid"; exit' EXIT
      subshell_pid="$(head -n 1)"
      head -n 10  # replacement for ./MyScript.sh
   )
echo ${PIPESTATUS[*]}
)