Ssh – Appending a string to a file from remote ssh

echosshtext processing

I want to ssh to a node (which is passwordless) and append $spool_as_final_name true to a file /var/spool/torque/mom_priv/config. Note that is mandatory to put $ in front of the string.

So, I wrote

ssh node01 "echo \"\$spool_as_final_name true\" >> /var/spool/torque/mom_priv/config"

However the file looks like

Dummy
 true

I intentionally wrote Dummy to show you that true is written in the second column.

How can I fix that?

Best Answer

Simply use,

ssh node1 'echo "\$spool_as_final_name true" >> /var/spool/torque/mom_priv/config'

Or you can use the cat command,

echo "\$spool_as_final_name true" | ssh node1 "cat >> /var/spool/torque/mom_priv/config"

Related Solutions

SSH – Remote Command in SSH Config File

There wasn't a way to do that, until OpenSSH 7.6. From manual:

RemoteCommand

Specifies a command to execute on the remote machine after successfully connecting to the server. The command string extends to the end of the line, and is executed with the user's shell. Arguments to RemoteCommand accept the tokens described in the TOKENS section.

So now you can have

RemoteCommand cd /tmp && bash

It was introduced in this commit.

Appending a line to a file if absent

The problem is that grep -v will match lines that do not match the expression, not files that do not match it...

So if your file has any lines that do not match it, grep -v will match those lines and so grep will return successful.

A better approach is to use a positive match for the keyword and then use || (instead of &&) to append the line if needed:

grep -q "keyword" /a/b/c.conf || echo "abc keyword" >> /a/b/c.conf

You probably got your test with echo "the line is absent" to say it was absent when it was indeed absent... And maybe to do nothing if that was the only line. If you test this further, I think you'll see that as long as it does have any lines that do not match keyword, you'll get a match.

I hope this clarifies it!

Best Answer

Related Solutions

SSH – Remote Command in SSH Config File

RemoteCommand

Appending a line to a file if absent

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