How to execute a remote command over ssh with arguments?

Question

In my .bashrc I define a function which I can use on the command line later:

function mycommand() {
    ssh [email protected] cd testdir;./test.sh "$1"
}

When using this command, just the cd command is executed on the remote host; the test.sh command is executed on the local host. This is because the semicolon separates two different commands: the ssh command and the test.sh command.

I tried defining the function as follows (note the single quotes):

function mycommand() {
    ssh [email protected] 'cd testdir;./test.sh "$1"'
}

I tried to keep the cd command and the test.sh command together, but the argument $1 is not resolved, independent of what I give to the function. It is always tried to execute a command

./test.sh $1

on the remote host.

How do I properly define mycommand, so the script test.sh is executed on the remote host after changing into the directory testdir, with the ability to pass on the argument given to mycommand to test.sh?

Answer 1

Do it this way instead:

function mycommand {
    ssh [email protected] "cd testdir;./test.sh \"$1\""
}

You still have to pass the whole command as a single string, yet in that single string you need to have $1 expanded before it is sent to ssh so you need to use "" for it.

Update

Another proper way to do this actually is to use printf %q to properly quote the argument. This would make the argument safe to parse even if it has spaces, single quotes, double quotes, or any other character that may have a special meaning to the shell:

function mycommand {
    printf -v __ %q "$1"
    ssh [email protected] "cd testdir;./test.sh $__"
}

• When declaring a function with function, () is not necessary.
• Don't comment back about it just because you're a POSIXist.

Starting Bash version 4.4, it can also be simplified to this:

function mycommand {
    ssh [email protected] "cd testdir;./test.sh ${1@Q}"
}

See ${parameter@operator} section in Shell Parameter Expansion.

Answer 2

I'm using the following to execute commands on the remote from my local computer:

ssh -i ~/.ssh/$GIT_PRIVKEY user@$IP "bash -s" < localpath/script.sh $arg1 $arg2

Answer 3

This is an example that works on the AWS Cloud. The scenario is that some machine that booted from autoscaling needs to perform some action on another server, passing the newly spawned instance DNS via SSH

# Get the public DNS of the current machine (AWS specific)
MY_DNS=`curl -s http://169.254.169.254/latest/meta-data/public-hostname`


ssh \
    -o StrictHostKeyChecking=no \
    -i ~/.ssh/id_rsa \
    [email protected] \
<< EOF
cd ~/
echo "Hey I was just SSHed by ${MY_DNS}"
run_other_commands
# Newline is important before final EOF!

EOF

Answer 4

Reviving an old thread, but this pretty clean approach was not listed.

function mycommand() {
    ssh [email protected] <<+
    cd testdir;./test.sh "$1"
+
}