sendmail启动脚本注释

hb_sz

断断续续看了几天unixshell编程，我终于能大概看懂这个脚本了。
-eq大概是等于的意思，-n不知道是什么意思。-z大概是为0的意思。


#!/bin/bash
#
# sendmail      This shell script takes care of starting and stopping
#               sendmail.
#
# chkconfig: 2345 80 30
# description: Sendmail is a Mail Transport Agent, which is the program \
#              that moves mail from one machine to another.
# processname: sendmail
# config: /etc/mail/sendmail.cf
# pidfile: /var/run/sendmail.pid

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
#/etc/sysconfig/network内容如下
#NETWORKING=yes
#HOSTNAME=localhost.localdomain

[ -f /etc/sysconfig/network ] && . /etc/sysconfig/network

# Source sendmail configureation.
#/etc/sysconfig/sendmail内容如下
#DAEMON=yes
#QUEUE=1h，表示轮询待发邮件队列每小时一次

if [ -f /etc/sysconfig/sendmail ] ; then
    . /etc/sysconfig/sendmail
else
    DAEMON=no
    QUEUE=1h
fi
#如果$SMQUEUE为0，则SMQUEUE=$QUEUE
#如果$SMQUEUE还是0，则$SMQUEUE=1h,1小时
[ -z "$SMQUEUE" ] && SMQUEUE="$QUEUE"
[ -z "$SMQUEUE" ] && SMQUEUE=1h


# Check that networking is up.
#如果NETWORKING被禁用，退出。
[ "${NETWORKING}" = "no" ] && exit 0

#如果文件/usr/sbin/sendmail不存在，则退出
[ -f /usr/sbin/sendmail ] || exit 0

#退出状态码初始为0
RETVAL=0
#设置进程名为sendmail
prog="sendmail"

#启动过程
start() {
    # Start daemons.

    echo -n $"Starting $prog: "
    if test -x /usr/bin/make -a -f /etc/mail/Makefile ; then
      make all -C /etc/mail -s
    else
      for i in virtusertable access domaintable mailertable ; do
        if [ -f /etc/mail/$i ] ; then
        #为sendmail(8)制作映射
        makemap hash /etc/mail/$i < /etc/mail/$i
        fi
      done
    fi
    /usr/bin/newaliases > /dev/null 2>&1
    #以守护进程方式加载sendmail
    daemon /usr/sbin/sendmail $([ "x$DAEMON" = xyes ] && echo -bd) \
            $([ -n "$QUEUE" ] && echo -q$QUEUE) $SENDMAIL_OPTARG
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch /var/lock/subsys/sendmail

    if ! test -f /var/run/sm-client.pid ; then
    echo -n $"Starting sm-client: "
    touch /var/run/sm-client.pid
    chown smmsp:smmsp /var/run/sm-client.pid
    daemon --check sm-client /usr/sbin/sendmail -L sm-msp-queue -Ac \
            -q $SMQUEUE $SENDMAIL_OPTARG
    RETVAL=$?
        echo
        [ $RETVAL -eq 0 ] && touch /var/lock/subsys/sm-client
        fi

    return $RETVAL
}

stop() {
    # Stop daemons.
    echo -n $"Shutting down $prog: "
    killproc sendmail
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sendmail
    if test -f /var/run/sm-client.pid ; then
        echo -n $"Shutting down sm-client: "
        killproc sm-client
        RETVAL=$?
        echo
        [ $RETVAL -eq 0 ] && rm -f /var/run/sm-client.pid
        [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sm-client
    fi
    return $RETVAL
}

# See how we were called.
#$1表示第一个参数
case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  restart|reload)
    stop
    start
    RETVAL=$?
    ;;
  condrestart)
    if [ -f /var/lock/subsys/sendmail ]; then
        stop
        start
        RETVAL=$?
    fi
    ;;
  status)
    status sendmail
    RETVAL=$?
    ;;
  *)
    echo $"Usage: $0 {start|stop|restart|condrestart|status}"
    exit 1
esac

exit $RETVAL