shell学习四-----特殊变量二

Love The Way You Lie 2022-06-11 08:16 294阅读 0赞

7、学习使用系统脚本  
/etc/init.d/rpcbind                  
\[root@node01 day2\]\# vi /etc/init.d/rpcbind   
\#! /bin/sh  
\#  
\# rpcbind       Start/Stop RPCbind  
\#  
\# chkconfig: 2345 13 87  
\# description: The rpcbind utility is a server that converts RPC program \\  
\#              numbers into universal addresses. It must be running on the \\  
\#              host to be able to make RPC calls on a server on that machine.  
\#  
\# processname: rpcbind  
\# probe: true  
\# config: /etc/sysconfig/rpcbind  
  
\# This is an interactive program, we need the current locale  
\[ -f /etc/profile.d/lang.sh \] && . /etc/profile.d/lang.sh  
\# We can't Japanese on normal console at boot time, so force LANG=C.  
if \[ "$LANG" = "ja" -o "$LANG" = "ja\_JP.eucJP" \]; then  
    if \[ "$TERM" = "linux" \] ; then  
        LANG=C  
    fi  
fi  
  
  
\# Source function library.  
. /etc/init.d/functions  
  
  
\# Source networking configuration.  
\[ -f /etc/sysconfig/network \] &&  . /etc/sysconfig/network  
  
  
prog="rpcbind"  
\[ -f /etc/sysconfig/$prog \] && . /etc/sysconfig/$prog  
  
  
RETVAL=0  
uid=\`id | cut -d\\( -f1 | cut -d= -f2\`  
  
  
start() \{  
        \# Check that networking is up.  
        \[ "$NETWORKING" = "yes" \] || exit 6  
  
  
        \[ -f /sbin/$prog \] || exit 5  
  
  
        \# Make sure the rpcbind is not already running.  
        if status $prog > /dev/null ; then  
                exit 0  
        fi  
  
  
        \# Only root can start the service  
        \[ $uid -ne 0 \] && exit 4  
  
  
        echo -n $"Starting $prog: "  
        daemon $prog $1 "$RPCBIND\_ARGS"  
        RETVAL=$?  
        echo  
        if \[ $RETVAL -eq 0 \] ; then       成功了，就创建一个文件，这里写脚本写个plog，启动建立，停止删掉  
                touch /var/lock/subsys/$prog  
                \[ ! -f /var/run/rpcbind.pid \] &&  
                        /sbin/pidof $prog > /var/run/rpcbind.pid  
        fi  
        return $RETVAL  
\}  
  
  
stop() \{  
        echo -n $"Stopping $prog: "  
        killproc $prog  
        RETVAL=$?  
        echo  
        \[ $RETVAL -eq 0 \] && \{  
                rm -f /var/lock/subsys/$prog   成功了，就创建一个文件，这里写脚本写个plog，启动建立，停止删掉  
                rm -f /var/run/rpcbind\*  
        \}  
        return $RETVAL  
\}  
  
  
\# See how we were called.  
case "$1" in                                  接传参，如果是以下的就执行。  
  start)  
        start  
        RETVAL=$?                             返回值给一个变量，返回给当前shell  
        ;;  
  stop)  
        stop  
        RETVAL=$?  
        ;;  
  status)  
        status $prog  
        RETVAL=$?  
        ;;  
  restart | reload| force-reload)  
        stop  
        start  
        RETVAL=$?  
        ;;  
  condrestart | try-restart)  
        if \[ -f /var/lock/subsys/$prog \]; then  
                stop  
                start -w  
                RETVAL=$?  
        fi  
        ;;  
  \*)  
        echo $"Usage: $0 \{start|stop|status|restart|reload|force-reload|condrestart|try-restart\}"   $0这里表示命令自己  
        RETVAL=2  
        ;;  
esac  
  
  
exit $RETVAL  
  
  
执行命令：  
\[root@node01 day2\]\# /etc/init.d/rpcbind start   这个start就是上面$1接收传参  
  
  
\[root@node01 day2\]\# /etc/init.d/rpcbind dddd fkdjkj  kjkjf  
Usage: /etc/init.d/rpcbind \{start|stop|status|restart|reload|force-reload|condrestart|try-restart\}  
\[root@node01 day2\]\#   
\[root@node01 day2\]\# /etc/init.d/rpcbind status  
rpcbind (pid  1292) is running...  
=======================================================================  
8、$\*和$@的区别（了解）  
$\*获取shell的所有传参，将所有的参数视为单个字符串，相当于“$1$2$3"  
$@他把所有参数显示为“$1" “1"  ”$3"  
注意：上述区别在于加双引号的时候，即“$\*" 和"$@"  
例子：  
\[root@node01 day2\]\# set -- "lao lang"  welcome to beijing  传入4个参数  
\[root@node01 day2\]\# echo $\#                                打印参数  
4  
\[root@node01 day2\]\# for i in "$\*";do echo $i;done  
lao lang welcome to beijing  
\[root@node01 day2\]\# for i in "$@";do echo $i;done  在有双引号的情况下去处理，每个单数独立输出  
lao lang  
welcome  
to  
beijing  
\[root@node01 day2\]\# for i in "$@";do echo $i;done   
lao lang  
welcome  
to  
beijing  
  
  
\[root@node01 day2\]\# for i in $\*;do echo $i;done   在没有双引号的情况下，把参数分开了，这样“$\*" 和"$@"结果一样了  
lao  
lang  
welcome  
to  
beijing  
\[root@node01 day2\]\# for i in $@;do echo $i;done    
lao  
lang  
welcome  
to  
beijing  
=====================================================================  
9、移动位置变量  内置变量  
\[root@node01 day2\]\# shift  
\[root@node01 day2\]\# for i in $@;do echo $i;done  
welcome  
to  
beijing  
\[root@node01 day2\]\# shift  
\[root@node01 day2\]\# for i in $@;do echo $i;done  
to  
beijing  
\[root@node01 day2\]\# shift  
\[root@node01 day2\]\# for i in $@;do echo $i;done  
beijing  
\[root@node01 day2\]\# shift  
\[root@node01 day2\]\# for i in $@;do echo $i;done  
  
  
\[root@node01 day2\]\# help shift  
shift: shift \[n\]  
    Shift positional parameters.  
      
    Rename the positional parameters $N+1,$N+2 ... to $1,$2 ...  If N is  
    not given, it is assumed to be 1.  
      
    Exit Status:  
    Returns success unless N is negative or greater than $\#.  
例子  
\[root@node01 day2\]\# vim \`which ssh-copy-id\`  
\#!/bin/sh  
  
  
\# Shell script to install your public key on a remote machine  
\# Takes the remote machine name as an argument.  
\# Obviously, the remote machine must accept password authentication,  
\# or one of the other keys in your ssh-agent, for this to work.  
  
  
ID\_FILE="$\{HOME\}/.ssh/id\_rsa.pub"  
  
  
if \[ "-i" = "$1" \]; then                                 如果$1是-i做shift  
  shift  
  \# check if we have 2 parameters left, if so the first is the new ID file  
  if \[ -n "$2" \]; then  
    if expr "$1" : ".\*\\.pub" > /dev/null ; then  
      ID\_FILE="$1"  
    else  
      ID\_FILE="$1.pub"  
    fi  
    shift         \# and this should leave $1 as the target name  
  fi  
else  
  if \[ x$SSH\_AUTH\_SOCK != x \] ; then  
    GET\_ID="$GET\_ID ssh-add -L"  
  fi  
fi  
if \[ -z "\`eval $GET\_ID\`" \] && \[ -r "$\{ID\_FILE\}" \] ; then  
  GET\_ID="cat $\{ID\_FILE\}"  
fi  
  
  
if \[ -z "\`eval $GET\_ID\`" \]; then  
  echo "$0: ERROR: No identities found" >&2  
  exit 1  
fi  
  
  
if \[ "$\#" -lt 1 \] || \[ "$1" = "-h" \] || \[ "$1" = "--help" \]; then  
  echo "Usage: $0 \[-i \[identity\_file\]\] \[user@\]machine" >&2  
  exit 1  
fi  
  
  
\{ eval "$GET\_ID" ; \} | ssh $1 "umask 077; test -d ~/.ssh || mkdir ~/.ssh ; cat >> ~/.ssh/authorized\_keys && (test -x /sbin/restorecon && /sbin/restorecon ~/.ssh ~/.ssh  
/authorized\_keys >/dev/null 2>&1 || true)" || exit 1  
  
  
cat <<EOF  
Now try logging into the machine, with "ssh '$1'", and check in:  
  
  
  .ssh/authorized\_keys  
  
  
to make sure we haven't added extra keys that you weren't expecting.  
  
  
EOF  
                                                                                                                                                     50,1          Bot  
  
  
if \[ -z "\`eval $GET\_ID\`" \]; then  
  echo "$0: ERROR: No identities found" >&2  
  exit 1  
fi  
  
  
if \[ "$\#" -lt 1 \] || \[ "$1" = "-h" \] || \[ "$1" = "--help" \]; then  
  echo "Usage: $0 \[-i \[identity\_file\]\] \[user@\]machine" >&2  
  exit 1  
fi  
  
  
\{ eval "$GET\_ID" ; \} | ssh $1 "umask 077; test -d ~/.ssh || mkdir ~/.ssh ; cat >> ~/.ssh/  
authorized\_keys && (test -x /sbin/restorecon && /sbin/restorecon ~/.ssh ~/.ssh/authorized  
\_keys >/dev/null 2>&1 || true)" || exit 1  
  
  
cat <<EOF  
Now try logging into the machine, with "ssh '$1'", and check in:  
  
  
  .ssh/authorized\_keys  
  
  
to make sure we haven't added extra keys that you weren't expecting.  
  
  
EOF  
  
===========================================================================  
10、其他  
$$ 获取当前shell的进程号（PID)：当系统中只能同时运行一个相同的脚本  
例子：  
\[root@node01 ~\]\# vi p.sh  
echo 1  
sleep 300  
~               
\[root@node01 day2\]\# sh pid.sh &  
\[2\] 10621  
\[root@node01 day2\]\#   
\[root@node01 day2\]\# ps -ef |grep pid.sh  
root      10621  10581  0 10:33 pts/1    00:00:00 sh pid.sh  
root      10627  10581  0 10:33 pts/1    00:00:00 grep pid.sh  
\[root@node01 day2\]\# vi pid.sh   
echo $$ >/tmp/a.pid  
sleep 300  
\[root@node01 day2\]\# sh pid.sh &  
\[3\] 10630  
\[root@node01 day2\]\# kill -USR2 \`cat /tmp/a.pid\`  
\[root@node01 day2\]\# ps -ef |grep pid.sh|grep -v grep  
\[root@node01 day2\]\# cat pid.sh   
\[root@node01 day2\]\# vi pid.sh    
\#!/bin/sh  
pidpath=/tmp/a.pid  
if \[ -f "$pidpath" \]  
  then  
      kill -USR2 \`cat $pidpath\` >/dev/null 2>&1  
      rm -f $pidpath  
fi  
echo $$ >$pidpath  
sleep 300  
~           
\[root@node01 day2\]\# ps -ef |grep pid.sh|grep -v grep  
root      10743      1  0 10:48 ?        00:00:00 sh pid.sh  
$! 执行上一个指令的PID  
$\_ 再此之前执行的命令或者脚本的最后一个参数  
=========================================================================  
以上变量重要程度

$?>$n>$\#>$0

=========================================================================

总结：                    
变量 含义   
$0 当前脚本的文件名   
$n 传递给脚本或函数的参数。n 是一个数字，表示第几个参数。例如，第一个参数是$1，第二个参数是$2。   
$\# 传递给脚本或函数的参数个数。   
$\* 传递给脚本或函数的所有参数。   
$@ 传递给脚本或函数的所有参数。被双引号(" ")包含时，与 $\* 稍有不同，下面将会讲到。   
$? 上个命令的退出状态，或函数的返回值。   
$$ 当前Shell进程ID。对于 Shell 脚本，就是这些脚本所在的进程ID。