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I am trying to execute a single command over ssh that contains `sub-code` or $(sub-code) (I use it all the time but I don't know the official name for that) to be executed first, but on the target server.

For the sake of argument, let's say this is the command I want to use. Ofcourse this can be done with hostname, but this is just a simplified example that contains all the formatting wizardry I want to use.

echo `uname -a | awk '{print $2}'`

No problem. But how do you escape this properly to send it over ssh in a single command? The following is wrong, because it lets the server reply your local hostname. The sub-code is executed locally:

ssh myServer echo `uname -a | awk '{print $2}'`

But any escape-ishness that comes to mind doesn't work:

$ ssh myServer echo \`uname -a | awk '{print $2}'\`
awk: cmd. line:1: {print $2}`
awk: cmd. line:1:           ^ invalid char '`' in expression
$ ssh myServer echo \$(uname -a | awk '{print $2}')
bash: syntax error near unexpected token `('
$ ssh myServer echo \$\(uname -a | awk '{print $2}')
bash: syntax error near unexpected token `)'
$ ssh myServer echo \$\(uname -a | awk '{print $2}'\)
awk: cmd. line:1: {print $2})
awk: cmd. line:1:           ^ syntax error
bash: -c: line 0: unexpected EOF while looking for matching `)'
bash: -c: line 1: syntax error: unexpected end of file

I would like an answer that includes using properly escaped ` or $() because I'd like to know if it's possible.echo` could be something more complicated.

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2
  • 1
    why echo `command`? why not command? Commented Feb 5, 2013 at 13:26
  • 1
    @anishsane because he wants to see how to pass a backtick or a $( through ssh to a remote server Commented Feb 5, 2013 at 13:32

6 Answers 6

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73

Try this

ssh myServer "uname -a | awk '{print \$2}' "

Use the double quotes " in order to group the commands you will execute remotely.

You also need to escape the $ in the $2 argument, so that it is not calculated locally, but passed on to awk remotely.

Edit:

If you want to include the $( ), you again have to escape the $ symbol, like this:

ssh myServer "echo \$(uname -a | awk '{print \$2}') "

You can also escape the backtick `, like this:

ssh myServer "echo \`uname -a | awk '{print \$2}'\` "
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3 Comments

@Redsandro I think I figured out how to escape the $( and the backtick on ssh. Just updated my answer...
If you execute in sub-command like res=`ls | awk '{print \\$2}'`, we need two escape here.
Yeah I was trying sshpass to execute /proc/loadavg on remote server and using awk to filter the result. Thanks for the answer. The escape sequence did the trick!. Thanks
10

It is better to use a heredoc with ssh to avoid escaping quotes everywhere in a more complex command:

ssh -T myServer <<-'EOF'
uname -a | awk '{print $2}'
exit
EOF
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7

Just some additional note:

In my case, the escape of the $ doesn't help:

ts1350:> ssh sysadm@node "grep feature features.txt| awk '{print $6}' "
Password: 
A  feature   -name  ue_trace_mme    | off
ts1350:> ssh sysadm@node "grep feature features.txt| awk '{print \$6}' "
Password: 
awk: cmd. line:1: {print \}
awk: cmd. line:1:        ^ backslash not last character on line
awk: cmd. line:1: {print \}
awk: cmd. line:1:        ^ syntax error
ts1350:> ssh sysadm@node "grep feature features.txt| awk '{print \\$6}' "
Password: 
awk: cmd. line:1: {print \\}
awk: cmd. line:1:        ^ backslash not last character on line
awk: cmd. line:1: {print \\}
awk: cmd. line:1:        ^ syntax error

While add a space between $ and the number works:

Fri Oct  4 14:49:28 CEST 2019
ts1350:> ssh sysadm@node "grep feature features.txt| awk '{print $ 6}' "
Password: 
off

Hope this secodnary way help someone like me.

Thanks to @dave in his answer: How to print a specific column with awk on a remote ssh session?

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1 Comment

While add a space between $ and the number works, this is amazing, thank you very much. I tried \' \$, almost everything, still does not work, frustrated.
5

What about piping the output of the command and run awk locally?

ssh yourhost uname -a | awk '{ print $2 } '
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1 Comment

Thanks, this works in certain cases. However, for more versatility, user000001's answer does exactly what I want. :)
4

The workaround is to create an sh file with the command then pass it to ssh command:

test.sh

echo `uname -a | awk '{print $2}'`

and command:

ssh myServer 'bash -s' < test.sh

UPDATE:

The command without quotes works fine as well:

ssh myServer uname -a | awk '{print $2}'
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5 Comments

@"The command without quotes works fine as well:" the awk being executed is local awk, not on the remote system.
Yes, commands from all 3 questions run the right part (after the pipe) locally. So the only solution is to save the command in the script.
Thanks, this works. Upvoted. But user000001 does exactly what I want in a single command, I've accepted that one. :)
"So the only solution is to save the command in the script" : I object the "only" word. probably you meant "easiest".
sorry, I mean answers. I've tested the last command of user000001 and it works on the remote server so I was wrong.
2

If you are trying to get the hostname, use:

ssh myServer "uname -n"

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