How to ssh from within a bash script?

Question

I am trying to create an ssh connection and do some things on the remote server from within the script.

However the terminal prompts me for a password, then opens the connection in the terminal window instead of the script. The commands don't get executed until I exit the connection.

How can I ssh from within a bash script?

halfdan · Accepted Answer · 2013-05-06T13:00:33.920

76

If you want the password prompt to go away then use key based authentication (described here).
To run commands remotely over ssh you have to give them as an argument to ssh, like the following:

root@host:~ # ssh root@www 'ps -ef | grep apache | grep -v grep | wc -l'

edited May 06 '13 at 13:00

answered Dec 13 '09 at 00:38

halfdan

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5

What if I have multiple lines (just for code clarity), how can I pass that to ssh? – blong Jan 24 '12 at 20:24
14

Use a semicolon as command seperator. `cd /var/www; cp foo bar;` – halfdan Jan 24 '12 at 23:00
2

@blong you can try a heredoc, see here: http://stackoverflow.com/a/4412338/5359531 – user5359531 Nov 03 '16 at 19:47
It's been ~4 years, so I've now come to know heredocs :) Still, thanks for sharing this @user5359531 ! – blong Nov 03 '16 at 19:53

score 21 · Answer 2 · answered Dec 13 '09 at 00:54

21

If you want to continue to use passwords and not use key exchange then you can accomplish this with 'expect' like so:

#!/usr/bin/expect -f
spawn ssh user@hostname
expect "password:"
sleep 1
send "<your password>\r"
command1
command2
commandN

answered Dec 13 '09 at 00:54

SiegeX

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-bash: ./test.sh: /usr/bin/expect: bad interpreter: No such file or directory – Hamza Saeed Aug 06 '20 at 08:05

score 5 · Answer 3 · answered Dec 13 '09 at 10:25

There's yet another way to do it using Shared Connections, ie: somebody initiates the connection, using a password, and every subsequent connection will multiplex over the same channel, negating the need for re-authentication. ( And its faster too )

# ~/.ssh/config 
ControlMaster auto
ControlPath ~/.ssh/pool/%r@%h

then you just have to log in, and as long as you are logged in, the bash script will be able to open ssh connections.

You can then stop your script from working when somebody has not already opened the channel by:

ssh ... -o KbdInteractiveAuthentication=no ....

score 2 · Answer 4 · answered Dec 13 '09 at 00:36

What you need to do is to exchange the SSH keys for the user the script runs as. Have a look at this tutorial

After doing so, your scripts will run without the need for entering a password. But, for security's sake, you don't want to do this for root users!

How to ssh from within a bash script?

4 Answers4

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