Linux RedHat daemon 功能使用
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RedHat daemon function usage
提问by quickshiftin
I'm working on an init script for Jetty on RHEL. Trying to use the daemonfunction provided by the init library (/etc/rc.d/init.d/functions).
我正在为 RHEL 上的 Jetty 编写一个初始化脚本。尝试使用daemoninit 库 ( /etc/rc.d/init.d/functions)提供的函数。
I found this terse documentation, and an online example(I've also been looking at other init scripts on the system for examples).
我找到了这个简洁的文档和一个在线示例（我也一直在查看系统上的其他 init 脚本以获取示例）。
Look at this snippet from online to start the daemon
从网上看这个片段来启动守护进程
daemon --user="$DAEMON_USER" --pidfile="$PIDFILE" "$DAEMON $DAEMON_ARGS &"
RETVAL=$?
pid=`ps -A | grep $NAME | cut -d" " -f2`
pid=`echo $pid | cut -d" " -f2`
if [ -n "$pid" ]; then
echo $pid > "$PIDFILE"
fi
Why bother looking up the $PIDand writing it to the $PIDFILEby hand? I guess I'm wondering what the point of the --pidfileoption to the daemonfunction is.
为什么要费心查找$PID并手写$PIDFILE？我想我想知道--pidfile该daemon功能的选项有什么意义。
采纳答案by jnas
To answer the question you guess that you have, is that --pidfileis used to check whether the daemon process is already running. On RHEL (and derivates) the daemonfunction won't write the pidfile.
回答你猜你有的问题，--pidfile是用来检查守护进程是否已经在运行。在 RHEL（和派生类）上，该daemon函数不会写入 pidfile。
In the case that the program stays in the foreground it has to be explicitly sent to the background by appending &to the command and the pid has to be fetched afterwards. $!is not usable when using daemon.
在程序停留在前台的情况下，它必须通过附加&到命令显式发送到后台，然后必须获取 pid。$!使用时不可用daemon。
