How can I pass a shell script variable into an Expect script?

Question

I want to pass the $SPACE variable into an Expect script and get the output and again pass into the shell script.

#!/bin/bash -x

    SPACE=$(df -h | awk '{ print $5 }' | grep -v Use |sort -n |tail -1 | cut -d % -f1)
    #set user "root"
    #set ip "192\.168\.53\.197"
    #echo $SPACE

    expect<<EOF

    spawn ssh "root\@192\.168\.53\.197"

    expect "Password:"

    send "Karvy123$\r";

    expect "prompt"

    send "$SPACE\r";

    expect "prompt"

    EOF

Answer 1

Oh, I see. You want $SPACE to hold the COMMAND, not the VALUE. This construct will execute the command and save the output in the variable: x=$(cmd arg arg). So you are finding the space used on your local host and sending that value to the remote host.

You need something like this:

#!/bin/bash
export cmd="df -h | awk '{ print \$5 }' | grep -v Use |sort -n |tail -1 | cut -d % -f1"
remote_usage=$(
    expect <<'EOF'
    log_user 0
    spawn -noecho ssh "root@192.168.53.197"
    expect "Password:"
    send "*****\r"
    expect "prompt"
    send "$env(cmd)\r"
    expect -re {(?n)^(\d+)$.*prompt}
    send_user "$expect_out(1,string)\n"
    send "exit\r"
    expect eof
EOF
)
echo "disk usage on remote host: $remote_usage"

However, you don't have to do any of that. Set up SSH keys (with ssh-keygen and ssh-copy-id) and do

remote_usage=$( ssh root@192.168.53.197 sh -c "df -h | awk '{ print \$5 }' | grep -v Use |sort -n |tail -1 | cut -d % -f1" )