I have an shell script which uses expect to launch a ssh session to another server and list a directory. It works fine but my question is what is the best way to handle remote prompts after logging in? For example, here is what I have so far:
# Wait for the prompt on a remote ssh server
-re "\[%|>|\$|#\] $" {
send "ls -1t /home/user/\r"
expect {
"*not found" {
puts "\nDirectory not found\n"
exp_continue
}
timeout { puts "\ntimeout happened\n" }
-re "\[%|>|\$|#\] $" {
puts "Exiting..."
send "exit\r"
return
}
}
}
So, after a successful login the expect script waits for the prompt before sending the ls -1t /home/user/ command. The prompt can be different depending how how the ssh destination is setup. So far I'm checking for
-re "\[%|>|\$|#\] $"
prompts handled so far....
%
>
$
#
I would like to make this as generic as possible so I know the destination ssh server is ready to receive the ls -1t /home/user/ command.
Is there a better way to do this or should I add more cases to the reg_ex in my expect script?
I've also tried -re ". $" but this doesn't work
Related
I wrote a bash code to send files to a sever computer from my remote laptop. I used 'scp' command and wrote it on a bash script to bypass entering a password every time I ran it.
expect <<EOF
spawn scp -P 1111 -o StrictHostKeyChecking=no -r /Users/Desktop/sync_mac user#192.111.111.101:/home/folder
expect "password:"
send "11111\r"
expect eof
EOF
However, the problem is when I ran the bash script on the terminal, it seemed like working well but suddenly failed sending files without any sign of warnings.(Especially for the case of sending a large number of files or a large size of file, it was okay for the case of a small number and a small size)
Thanks for your help
The default timeout for expect is 10 seconds so expect eof would wait for at most 10 seconds which may be not enough for many files as you mentioned.
To fix, you can set timeout -1 before expect eof or just expect -timeout -1 eof.
I had to do this a while back, but for multiple servers, the list of which would change from night to night. I discovered sometimes scp would ask to add the host to your list of known hosts first, or other messages for which I had to code handling. That could be getting buried in your script.
This is an excerpt of what ultimately worked, if that helps:
expect -c "
spawn ssh-copy-id -i /x/home/$USER/.ssh/id_rsa.pub $USER#$HOST
expect {
\"password:\" {
send \"$PASS\n\"
expect {
\"expecting.\" { }
timeout {exit 1}
\"again.\" {exit 1}
}
}
\"yes/no)?\" {
send \"yes\n\"
expect \"password:\" {
send \"$PASS\n\"
expect {
\"expecting.\" { }
timeout {exit 1}
\"again.\" {exit 1}
}
}
}
}
How do I do the following?
SSH to a machine, probably using expect since this is a script and I can't type the password for it
Wait for a prompt from the machine. The prompt is ->
Then send a bunch of commands from the original host to the machine I ssh'd to. Note that the output from these commands can contain the characters ->
Exit
Here are the contents of some-commands.txt:
first command
second command
third command
Here are the contents of the expect script:
#!/usr/bin/expect
set f [open "some-commands.txt"]
set cmds [split [read $f] "\n"]
close $f
eval spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no root#machine
interact -o -nobuffer -re "Password:" return
send "password\r"
# look for the prompt
set prompt "\n-> "
foreach cmd $cmds {
send "$cmd\r";
# The following works, except for the commands
# whose output include ->
interact -o -nobuffer -re "-> " return
}
The problem is that the interact command captures the -> from the command output instead of the prompt, which hasn't yet arrived at that point.
I'm used to accomplish the same thing by doing something like:
ssh -t -t -C user#host 'bash -s' < my_shell_script.sh param1 paramX
Where my_shell_script.sh is an simple shell script.
The trick here is use multiple -t to force pseudo-terminal over ssh and the -s option to bash witch makes it reads the commands from the standard input.
I am really new to using expect, and a bit confused regarding passing commands to an expect script, so please bear with me... I have searched numerous forums, but cannot seem to find an example of an expect script that uses the read command to get user input.
In my Korn shell script, I call an expect script (expectssh.exp) to ssh login to another host and get user input regarding that host's network configuration (network interface card number and subnet mask information). I pass four arguments to the expect script: the remote host ip address, the username, the password, and the list of commands to run. My expect script is below:
#!/usr/bin/expect
# Usage: expectssh <host> <ssh user> <ssh password> <script>
set timeout 60
set prompt "(%|#|\\$) $"
set commands [lindex $argv 3];
spawn ssh [lindex $argv 1]#[lindex $argv 0]
expect {
"*assword:" {
send -- "[lindex $argv 2]\r"
expect -re "$prompt"
send -- "$commands\r"
}
"you sure you want to continue connecting" {
send -- "yes\r"
expect "*assword:"
send -- "[lindex $argv 2]\r"
expect -re "$prompt"
send -- "$commands\r"
}
timeout {
exit }
}
The script runs well, except that when it gets to the 'read' command, the script does not continue or exit after the user presses enter. It just hangs.
The commands I pass to the expect script and its call are as follows:
SCRIPT='hostname > response.txt;netstat -rn;read net_card?"What is the network interface card number? " >> response.txt; read net_mask?"What is the subnet mask? " >> response.txt'
/usr/bin/expect ./expectssh.exp $hostip $usr $pswd "$SCRIPT"
Any suggestions on how I can pass the read command through my expect script without it hanging?
On a side note because I know it will come up - I am not allowed to do key-based automatic SSH login. I have to prompt for a username and password, which is done from the Korn shell script that calls this expect script.
Thanks for any suggestions and help you can provide!
For anyone interested, I was able to get the read command to work for user input by doing a few things:
(1) Putting it within an -re $prompt block instead of appending send -- "$commands\r" after the password entry.
(2) Hard coding the commands into the script rather than passing them in.
(3) Following the command with an interact statement so that the next send command isn't entered before the user responds.
My expect block now looks like this:
expect {
-re "(.*)assword:" {
send -s "$pswd\r"
exp_continue
}
"denied, please try again" {
send_user "Invalid password or account.\n"
exit 5
}
"incorrect" {
send_user "Invalid password or account.\n"
exit 5
}
"you sure you want to continue connecting" {
send -s "yes\r"
exp_continue
}
-re $prompt {
set timeout -1
send -- "hostname > partnerinit\r"
expect -exact "hostname > partnerinit\r"
send -s "netstat -rn\r"
expect -re "$prompt"
send -- "read n_card?'Enter the network interface card number for this server (i.e. eth0): '\r"
interact "\r" return
send -- "\r"
send -- "echo \$n_card >> partnerinit\r"
send -- "msk=\$(cat /etc/sysconfig/network-scripts/ifcfg-\$n_card | grep NETMASK)\r"
send -- "msk=\$(echo \${msk#NETMASK=})\r"
send -- "echo \$msk >> partnerinit\r"
send -- "cat partnerinit\r"
set retval 0
}
timeout {
send_user "Connection to host $host timed out.\n"
exit 10
}
eof {
send_user "Connection to host $host failed.\n"
exit 1
}
}
I also updated the script to automatically determine the subnet mask based on the network interface card number entered by the user. It was brought to my attention that finding the network interface card number would be very difficult to automate in the case of a box that has multiple interface cards. Better to start small and have the user enter it and fine-tune/automate it later once the overall script is working.
Now I'm working on modifying this to scp my partnerinit file back to my local host and to return meaningful exit statuses from each of the expect conditions.
After i use expect access ssh, and run particular command in it. How could i get the actually return value of that command and set it to the return value of expect or an env variable(better)?
I am not so familiar with expect, so a few lines to show how the capture thing works would help a lot. Many thanks.
You do it the same way you would sitting at a terminal: echo $? (I assume your remote shell is sh/ksh/bash/...)
#!/usr/bin/expect -f
set host remote_host
set user remote_username
set prompt {\$ $}
set cmd {grep not-found /etc/passwd}
log_user 0
spawn ssh -l $user $host
expect -re $prompt
send "$cmd\r"
expect -re $prompt
send -- "echo \$?\r"
expect -re "\r\n(\\d+)\r\n.*$prompt"
set rc $expect_out(1,string)
send -- "exit\r"
expect eof
puts "return code from '$cmd' on $host = $rc"
The following expect script works fine when the Linux machine asks for a password after login. But some of our Linux machines don't need a password for SSH (we can login without a password), so I need to change the expect script in order to support machines without a password. How can I do that?
$ expect_test=`cat << EOF
set timeout -1
spawn ssh $IP hostname
expect {
")?" { send "yes\r" ; exp_continue }
word: {send "pass123\r" }
}
expect eof
EOF`
$ expect -c "$expect_test"
When running on a machine that needs a password:
$ IP=10.17.18.6
$ expect -c "$expect_test"
spawn ssh 10.17.18.6 hostname
sh: /usr/local/bin/stty: not found
This computer system, including all related equipment, networks and network devices (specifically including Internet access),is pros
yes
Password:
Linux1_machine
When running on a machine that doesn't need a password:
$ IP=10.10.92.26
$ expect -c "$expect_test"
spawn ssh 10.10.92.26 hostname
sh: /usr/local/bin/stty: not found
Linux15_machine
expect: spawn id exp5 not open
while executing
"expect eof"
Use this expect command:
expect {
")?" {send "yes\r"; exp_continue}
word: {send "pass123\r"; exp_continue}
eof
}
That way, if EOF is encountered before "password:", the script will act normally.
Change you timeout from -1 to something else, this will cause expect to move on to the next line if the expected string does not show up within the given timeout.
The current value, -1 causes it to block forever if not password is prompted for.
UPDATE:
set timeout 5
spawn ssh $IP hostname
expect {
")?" { send "yes\r" ; exp_continue }
word: {send "pass123\r" }
eof {exit}
}