RETVAL是什么意思？

Question

我正在尝试为start和stop服务的脚本创建一个模板。我检查了tomcat启动和停止的模板，并看到了命令RETVAL=$?。

这是做什么的？我应该留着它吗？顺便说一下，我的脚本在下面，如果你们想看的话。

#!/bin/bash
#===================================================================================
#
#
FILE: <script-file-name>.sh
#
#
USAGE: <script-file-name>.sh [-d] [-l] [-oD logfile] [-h] [starting directories]
#
# DESCRIPTION: List and/or delete all stale links in directory trees.
#
The default starting directory is the current directory.
#
Don’t descend directories on other filesystems.
#
#
OPTIONS: see function ’usage’ below
# REQUIREMENTS: ---
#
BUGS: ---
#
NOTES: ---
#
AUTHOR: Valter Henrique, valter.henrique@<company>.com
#
COMPANY: <company>
#
VERSION: 1.0
#
CREATED: 03.14.13
#
REVISION: 03.14.13
#===================================================================================
#
# chkconfig: 345 90 12
# description: <service-name> start, stop, restart service
#
# Get function from functions library
. /etc/init.d/functions

folder=/<company>/<service-folder> #folder to the application
service="<service-name>" #name of the service

startup=$folder/start.sh
shutdown=$folder/stop.sh


#=== FUNCTION ================================================================
#
NAME: start
# DESCRIPTION: Start the service <service-name>
# PARAMETER 1: ---
#===============================================================================
start() {

  #----------------------------------------------------------------------
  # logging the start
  #----------------------------------------------------------------------
  initlog -c "echo -n Starting $service:"

  #----------------------------------------------------------------------
  # getting the process PID
  #----------------------------------------------------------------------    
  pid_process=`ps -ef | grep "$folder/<jar>.jar" | grep -v grep |awk -F' ' '{ print $2 }'`;

  if [ $pid_process ]; then
    echo "<service-name> is running!"
    echo "Stop then first!"
  else
    action $"Starting <service-name> service: " su - <user_deployer> -c $startup
    RETVAL=$?
  fi
  #----------------------------------------------------------------------
  # create the lock file
  #----------------------------------------------------------------------
  touch /var/lock/subsys/$service
  success $"Sucess $service startup"
  echo
}

#=== FUNCTION ================================================================
#
NAME: stop
# DESCRIPTION: Stop the service <service-name>
# PARAMETER 1: ---
#===============================================================================
stop() {
  #----------------------------------------------------------------------
  # logging the stop
  #----------------------------------------------------------------------
  initlog -c "echo -n Stopping $service: "
  killproc $service
  #----------------------------------------------------------------------
  # now, delete the lock file
  #----------------------------------------------------------------------
  rm -f /var/lock/subsys/$service
  echo
}

#----------------------------------------------------------------------
# Main Logic
#----------------------------------------------------------------------
case "$1" in
  start)
        start
        ;;
  stop)
        stop
        ;;
  status)
        status $service
        ;;
  restart|reload|condrestart)
        stop
        start
        ;;
  *)
        echo $"Usage: $0 {start|stop|restart|reload|status}"
        exit 1
esac 
exit 0

Answer 1

$?给出了上一次执行的命令的状态。在您的示例中，最后执行的命令是action....。此命令的退出状态将显示在稍后在RETVAL变量中捕获的$?中。如果命令成功，$?将包含0，否则为非零值。

Answer 2

RETVAL是一个变量。$？正在将上次执行的命令的状态赋给RETVAL变量。

Answer 3

正如其他人所说，$?是最后一个命令的退出状态。

现在，关于你的问题...

RETVAL不会在脚本中的其他地方使用，但请记住，在bash中，常规变量是全局变量，因此它们可以被其他函数使用。如您所见，可能会有一个success调用使用它。在我检查过的发行版中，/etc/init.d/functions没有使用这个变量，所以这行代码只是噪声，可以删除。检查你的发行版，看看它是做什么的。