How to send a password with a $ symbol in Expect Script

Question

I have an expect script that I need to login to a remote system and execute commands. This script works with the exception of providing the password to the root account. The root password contains a dollar sign that I cannot seem to get to work. Here is the code

#!/usr/bin/expect
set timeout 3
set username "root"
set password "Pas$word"
set hostname [lindex $argv 0]
log_user 0

send_user "\n#####\n# $hostname\n#####\n"

spawn ssh -q -o StrictHostKeyChecking=no $username@$hostname

expect {
    timeout { send_user "\nFailed to get password prompt\n"; exit 1 }
    eof { send_user "\nSSH failure for $hostname\n"; exit 1 }
    "*assword"
}

send "$password\r"

expect {
    timeout { send_user "\nLogin failed. Password incorrect.\n"; exit 1}
    "*\$ "
}

send_user "\nPassword is correct\n"

expect "$ " { send "ls" }

I have verified this works when providing credentials whose passwords don't contain the dollar sign, but I can't get it to work with the root account. It always produces the Login failed. Password incorrect timeout error. Changing the password is not an option. I have tried to supply the \ escape character in the password definition like so:

set password "Pas\$word"

And I get the same results... any ideas on what I'm doing wrong?

Thanks

EDIT As I said. I already tried to escape the $ character. But to clarify, I added a print statement for the password when the script starts up to verify the variable contains the password correctly... Here is the change:

set password "Pas\$word"
...
send_user "\n#####\n# $hostname\n#####\n"
send_user "Using password: $password\n"
...

Here is the console output:

njozwiak@ubuntu:~$ ./ssh_ls.sh 192.168.5.93

#####
# 192.168.5.93
#####
Using password: Pas$word

Login failed. Password incorrect.

Get rid of the quotes wherever you are using set. Checkout my answer. — SSaikia_JtheRocker, Jul 29 '13 at 17:24
I would think `set password {Pas$word}` should be sufficient. Run your script with `expect -d ssh-ls.sh` to see what's happening in the background. — glenn jackman, May 14 '14 at 16:45

score 9 · Answer 1 · answered Oct 27 '15 at 09:42

9

Try escaping the backslash, that is

Pas$word

becomes

Pas\\\$word

This is a common problem with scripting (even with PHP, Python) where a string gets unescaped twice or even more times!

A full-blown example how I use expect with SFTP, inside a Bash script:

#!/bin/bash
host=mysftp.dmz
port=22
username=john

/usr/bin/expect <<EOF
set timeout -1
spawn sftp -C -oPort=$port $username@$host
expect "password:"
send "Pas\\\$word\r"
expect "sftp>"
send "get data.txt\r"
expect "sftp>"
send "bye\r"
EOF

answered Oct 27 '15 at 09:42

John Mayor

577
6
13

Why do we need three backslashes instead of one? – zyy Apr 02 '20 at 13:59
@zyy: Because the "string gets unescaped **twice**" during the process: 1. unescape("Pas\\\$word") => "Pas\$word", 2. unescape("Pas\$word") => "Pas$word" – John Mayor May 29 '20 at 15:41
Thanks, I will check. – zyy May 29 '20 at 21:14

score 8 · Answer 2 · answered Aug 18 '17 at 15:42

I've found a makeshift solution for this. I'm sure this problem solved long ago, just mentioning how I solved mine:

Actual password:
Pas$word

Assign to variable password:
set password {Pas\$word}

In TCL(or expect in your code), grouping words within double braces {} disables substitution within the braces, thus your password will be stored as: Pas\$word
Now in the end, when you send password via expect Pas\$word will be translated as Pas$word which is the actual password.

But the problem is if the password is unknown, for example, password is in an encrypted file or has to be taken as user input. I was looking for this type of cases where I don't know where and how many $ sings are in the password.

Genius! But just letting people who were trying to escape all bash symbols, you don't need to escape `@` — ba11b0y, Jul 28 '21 at 07:10

score 4 · Answer 3 · answered Jan 22 '15 at 21:42

4

I was unable to get this working by just escaping the dollar sign. I did have luck by using \x to specify the hex value for the dollar sign.

set password "Pas\x24word"

answered Jan 22 '15 at 21:42

Jonathan Crowe

41
3

score 2 · Answer 4 · answered Mar 01 '17 at 15:04

I found this question because I had the same issue, I know it's an old question but for whoever is also still looking for a quick solution:

set CorrectedPassword [ string map -nocase { "\$" "\\\$" } $MyPassword ]

The $CorrectedPassword is then accepted by the login procedure. The -nocase is not needed, but I find it safer to include by default.

score 1 · Answer 5 · answered Jul 18 '17 at 19:21

1

I had a similar issue where I wanted to pass fileName with "$" in expect script and following worked for me

filePath=$(echo -n $filePath | sed -e 's/\$/\\\$/g')

answered Jul 18 '17 at 19:21

Vaibhav Fouzdar

199
1
4

score 1 · Answer 6 · edited Dec 15 '20 at 13:42

1

I used below and it worked for me :

send \"Pas\\\$word\"

edited Dec 15 '20 at 13:42

Giacomo1968

25,759
11
71
103

answered Dec 12 '17 at 00:18

Sky

215
1
3
11

SSaikia_JtheRocker · Answer 7 · 2013-07-29T17:20:45.257

-1

This should definitely help -

set username root
set password Pas\$word

Get rid of the quotes.

Hope this helps.

edited Jul 29 '13 at 17:20

answered Jul 29 '13 at 17:09

SSaikia_JtheRocker

5,053
1
22
41

No quotes produces the same results as with quotes. `Login failed. Password incorrect.` – linsek Jul 29 '13 at 17:40
Note that without the quotes, the password is displayed the same from the console output as with quotes. "Using password: Pas$word" – linsek Jul 29 '13 at 17:41
@njozwiak - What about set username root? Did you get rid of the quotes there too? – SSaikia_JtheRocker Jul 29 '13 at 17:55
@njozwiak - I'm saying this because I have just tried that in my machine and it's working quite fine. :) – SSaikia_JtheRocker Jul 29 '13 at 17:59

score -1 · Answer 8 · answered Aug 14 '13 at 22:08

-1

I had a similar problem recently. This worked for me:

$ PASS="pa\$\$word"; somecommand --user uname --password $PASS

Notice double quotes and the semicolon.

answered Aug 14 '13 at 22:08

wnet

1

1) Your solution is for `pa$$word`, not for `pas$word`, and 2) with _expect_ you need to escape the string twice: `pas\\\$word` – John Mayor Oct 27 '15 at 13:49

How to send a password with a $ symbol in Expect Script

8 Answers8