start() {# ()创建子进程(flock -x 200 # 200 文件描述符，进程级别的。ctl_n=$(ps -fu ${USER} | grep 'xxx start' | grep -v 'grep' | grep -v "$$" | wc -l) # grep -v "$$" 过滤掉当前进程if [ ${ctl_n} -gt 1 ]; thenecho -e "Exist kafka_ctl is running, please try later"return 1fireturn 0) 200>${lock_file}rc=$?if [ $rc -ne 0 ]; then # 子进程被异常中断rc=137，这种场景视业务情况继续执行业务逻辑或者退出脚本exit 0fi...
# start service}
分析：
通过flock锁定启动脚本，确保运行时有且仅有一个执行service start流程，通过检查和恢复备份确保下一次service start流程中配置信息的正确性，备份流程增加启动流程的容错性。
异常场景分析：
1. 调用脚本的start方法启动服务时如果收到了crtl + z信号
Ctrl + Z 时，运行中的脚本会接收到 SIGTSTP 信号，导致脚本被暂停并放入后台。此时，脚本并不会终止，而是处于暂停状态。要恢复脚本的运行，可以通过以下方法将其从后台重新调入前台或在后台继续运行。
使用 jobs 命令查看当前 Shell 中的所有后台任务。
jobs
[1]+ Stopped kafka_ctl start
使用 fg 命令将指定的任务恢复到前台运行
fg %1
2. 调用脚本的start方法启动服务时如果收到了crtl + c信号(中断信号)
当你按下 Ctrl + C 时，系统会向当前运行的前台进程发送 SIGINT（中断信号）。这是操作系统提供的一种机制，允许用户手动中断正在运行的程序或脚本。
...
}
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