从telnet会话中提取eth0的ip地址

Question

我需要自动化一个与远程设备一起工作的进程，

这是步骤

1. 远程登录
2. 输入用户名
3. ifconfig eth0 | grep'inet addr'| cut -d'：' - f 2 |切-d'' - f 1
4. 记下显示的ip并使用该ip地址完成剩余的进程。

已知的ip是telnet_ip，我想检索我可以进入的ip地址。

我想将这四个步骤自动化为一个名为get_ip的函数，它回显出ip地址。我想用这个函数如下

SSH_IP=$(get_ip 127.0.0.1 1000)

我环顾四周，看到有可能使用expect。我写过这个函数

function get_ip(){
expect << EOF
spawn telnet $1 $2
expect -ex "Escape character is '^]'."
send  "\r"
expect {
    -re ".*login: " {
        send "root\r"
    }
}
expect -re ".*root:~# "
send "ifconfig eth0 | grep 'inet addr' | cut -d ':' -f 2 | cut -d ' ' -f 1\r"
expect eof
send "\x1b\r"
expect "telnet>"
send "q\r"
puts "Address is $IPADDR"
EOF
}

运行此功能，我在屏幕上看到了ip地址，但它没有在变量SSH_IP中捕获。

我需要两个方面的帮助：1。我该怎么办才能让SSH_IP包含ip地址。 2.我怎样才能使expect默默地完成所有这些并返回结果？

请告诉我是否有任何其他方法可以实现相同的目标。

Answer 1

这是期望是PITA的一个领域：捕获命令输出。你会想要这样做：

function get_ip(){

    # pass the shell function params via the environment, so we can quote the expect script
    host=$1 port=$2 expect << 'EOF'

        # use `log_user` and `spawn -noecho` to stop output to stdout
        log_user 0
        spawn -noecho telnet $env(host) $env(port)

        expect -ex "Escape character is '^]'."
        send  "\r"
        expect "login: "
        send "root\r"
        expect "root:~# "

        send "ifconfig eth0\r"      # expect can parse the output, don't need a pipeline
        expect -re "(.*)root:~# "   # note the captured part
        set ip_addr [regexp -inline {inet addr:(\S+)} $expect_out(1,string)]
        puts "Address is $ip_addr"

        send "\x1b\r"
        expect "telnet>"
        send "q\r"

        # NOW you expect eof
        expect eof

EOF
}

我们甚至可以使用expect模式捕获它：

        send "ifconfig eth0\r"
        expect -re ".*inet addr:(\S+).*root:~# "
        puts "Address is $expect_out(1,string)"

Tcl命令文档：https://tcl.tk/man/tcl8.6/TclCmd/contents.htm

Answer 2

我决定和tmux一起去，而不是expect。这是我的解决方案

#! /bin/env bash
WINDOW_NAME=TELNET
DEBUG=
function dbbg(){
    [[ "$DEBUG" ]] && echo "DEBUG: $@"
}

function cleanup(){
    [[ "$DEBUG" ]] || tmux kill-window -t ${WINDOW_NAME} > /dev/null 2>&1
}

trap cleanup EXIT

if [ $# -eq 0 ]
then
    echo "Usage $(basename $0) <telnet ip> <telnet port>"
    exit 0
fi

# Start the work with sessions
tmux has-session 2>/dev/null
if [ "$?" -eq 1 ]
then
    dbbg "No Session found.  Creating and configuring."

    tmux new-session -d
else
    dbbg "Session found."
fi
tmux has-session -t :${WINDOW_NAME} 2>/dev/null
if [ "$?" -eq 1 ]
then
    dbbg "No window found. Creating a window named ${WINDOW_NAME}"

    tmux new-window -d -n ${WINDOW_NAME}
else
    dbbg "Window found."
fi

dbbg "connecting to tmux ip: $1 port: $2"
tmux send-keys -t :${WINDOW_NAME} "telnet $1 $2" Enter
sleep 2

answer="$(tmux capture-pane -t :${WINDOW_NAME} -p | sed '/^$/d' | tail -n 1)"
dbbg $answer
if [ "$answer" != "Escape character is '^]'." ] 
then
    echo "Telnet is occupied at the moment, try later"
    exit 1
fi

tmux send-keys -t :${WINDOW_NAME} Enter
sleep 2
answer="$(tmux capture-pane -t :${WINDOW_NAME} -p | sed '/^$/d' | tail -n 1)"
dbbg $answer
if [ "$answer" == "login:" ] 
then
    dbbg "Inputing user"
    tmux send-keys -t :${WINDOW_NAME} "root" Enter
    sleep 2
fi
tmux send-keys -t :${WINDOW_NAME} "ifconfig eth0 | grep 'inet addr' | cut -d ':' -f 2 | cut -d ' ' -f 1" Enter
sleep 2

ip_addr="$(tmux capture-pane -t :${WINDOW_NAME} -p | sed '/^$/d' | tail -n 2 | head -n 1)"

tmux send-keys -t :${WINDOW_NAME} C-]
sleep 2
tmux send-keys -t :${WINDOW_NAME} "q" Enter
echo $ip_addr