Unable to check if file exists on remote server using expect

Shell Programming and Scripting
1

Hi,

I need to check if a file exists on remote server using expect.

#!/bin/bash
ip_addr=10.10.10.10
user=root
passwd=Help
filename=/root/test
expect -c "
spawn ssh -n -T -o NumberOfPasswordPrompts=3 -o StrictHostKeyChecking=no $user@$ip_addr
expect \"*?assword:*\"
send -- \"$passwd\r\"
expect {
\"ls $filename\" { exp_continue }
$filename { puts found }
timeout { puts \"timed out\" }
}
"

The above code is not working. I need to capture the output and if file does not exist, i need to perform some steps. Any other approach using expect only will be appreciated as I cannot do key sharing.
Please help.

2

I have not used expect so much, but may be you can pass in the ls command in the ssh itself, like so

spawn ssh ..... "ls $filename"

I have come across similar situations before, but in my case, I have always been able to add the public key to the remote host so i dont need password, and then I simply

ssh hostname ls $file
if [ $? -ne 0 ]; then
  echo "handle missing file here"
fi
3

Thank you linuxpenguin, but i need to do it via expect only, as my task does not allow key sharing.So i have to send the password via expect only.

4

I was able to solve the issue.Please find below the code

#/bin/bash

ip_addr=10.10.10.10.
user=root
passwd=Help
filename=test_backup.sh
path=/root/


VAR=$(expect -c "
                    spawn ssh -n -T -o NumberOfPasswordPrompts=3 -o StrictHostKeyChecking=no $user@$ip_addr \"ls $path/$filename\"
                    expect \"*?assword:*\"
                    send -- \"$passwd\r\"
                    expect {
                        \"$path/$filename\" {
                        exit 0
                        }
                        \"ls: $path/$filename: No such file or directory\" {
                        exit 1
                        }
                    }
                    expect eof
                    ")
                echo "$VAR" | grep -q -e "No such file"
                if [ $? -eq 0 ];then
                VAR=$(expect -c 2> /dev/null "
                        spawn scp -q -o NumberOfPasswordPrompts=3 -o StrictHostKeyChecking=no $path/$filename $user@$ip_addr:$path
                        expect \"*?assword:*\"
                        send -- \"$passwd\r\"
                        send -- \"\r\"
                        expect eof
                        ")
                else
                    echo "$filename already exists at ip address $ip_addr at path $path"
                fi
1 Like
5

Thanks for the update!

6

If your administrator does not allow you to use keys for security reasons, they will be livid to discover you getting around this limitation with an insecure third-party brute forcing tool.

1 Like
7

@Corona688 I understand the point you are making, but then as of now, this has to be implemented like this only. After some time, they will move to key sharing..