解決

#!/bin/bash
function randbool() {
   if (( RANDOM %2 )); then
     true
   else
     false
   fi
}

while :
do
  randbool
  if [ $? -eq 0  ]; then
    echo 'break'
    break
  else
    echo "wait 1 sec."
    sleep 1
  fi
done
$ infinity_loop.sh
wait 1 sec.
wait 1 sec.
wait 1 sec.
wait 1 sec.
break

Bash: Random numbers for fun and profit