CODEWITHSUNDEEP
bashssh
William Abma
William Abma

Reputation: 495

Bash: get output of sudo command on remote using SSH

I'm getting incredibly frustrated here. I simply want to run a sudo command on a remote SSH connection and perform operations on the results I get locally in my script. I've looked around for close to an hour now and not seen anything related to that issue.

When I do:

#!/usr/bin/env bash

OUT=$(ssh username@host "command" 2>&1 )
echo $OUT

Then, I get the expected output in OUT.

Now, when I try to do a sudo command:

#!/usr/bin/env bash

OUT=$(ssh username@host "sudo command" 2>&1 )
echo $OUT

I get "sudo: no tty present and no askpass program specified". Fair enough, I'll use ssh -t.

#!/usr/bin/env bash

OUT=$(ssh -t username@host "sudo command" 2>&1 )
echo $OUT

Then, nothing happens. It hangs, never asking for the sudo password in my terminal. Note that this happens whether I send a sudo command or not, the ssh -t hangs, period.

Alright, let's forget the variable for now and just issue the ssh -t command.

#!/usr/bin/env bash

ssh -t username@host "sudo command" 2>&1

Then, well, it works no problem.

So the issue is that ssh -t inside a variable just doesn't do anything, but I can't figure out why or how to make it work for the life of me. Anyone with a suggestion?

Upvotes: 3

Views: 1258

Answers (2)

Joe Coder
Joe Coder

Reputation: 4525

In this situation, you can use tee to reveal the sudo prompt while also capturing the output of the ssh command in a temp file.

tempfile=$(mktemp)
ssh -t username@host "sudo command" | tee $tempfile

Keep in mind that this will also capture the sudo prompt and all stderr output from the remote shell in the output file, because stdout & stderr are both connected to the client shell's stdout when using ssh -t.

Upvotes: 0

alfunx
alfunx

Reputation: 3150

If your script is rather concise, you could consider this:

#!/usr/bin/env bash

ssh -t username@host "sudo command" 2>&1 \
    | ( \
        read output
        # do something with $output, e.g.
        echo "$output"
    )

For more information, consider this: https://stackoverflow.com/a/15170225/10470287

Upvotes: 3

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