How to pass bash's $@ over ssh accounting for spaces in arguments?

When working with the Bash shell, it is common to use the $@ variable to pass arguments to a script or command. However, when using ssh to execute a command on a remote server, passing arguments that contain spaces can be a bit tricky. In this article, we will explore how to pass $@ over ssh while accounting for spaces in arguments.

Before we dive into the solution, let's first understand the problem. When you execute a command using ssh, the remote server receives the command as a single string. This means that if you pass arguments containing spaces, the remote server will treat them as separate arguments, rather than a single argument with spaces.

For example, if you have a script called my_script.sh that takes two arguments, and you want to execute it over ssh like this:

$ ssh user@remote-server "my_script.sh arg1 arg2"

The remote server will receive the command as:

my_script.sh arg1 arg2

However, if one of the arguments contains a space, like:

$ ssh user@remote-server "my_script.sh arg1 "arg 2""

The remote server will receive the command as:

my_script.sh arg1 arg 2

This can lead to unexpected behavior, as the script may interpret arg and 2 as separate arguments.

To overcome this issue, we can enclose the entire command within single quotes (') instead of double quotes ("). This ensures that the remote server receives the command as a single string, preserving the spaces in the arguments.

Here's how you can modify the ssh command to pass $@ accounting for spaces:

$ ssh user@remote-server 'my_script.sh "$@"' -- arg1 "arg 2"

In this command, we use single quotes to enclose the entire command, including the script name and the $@ variable. The $@ variable is enclosed within double quotes to ensure that each argument is treated as a separate entity.

The -- after the command is used to separate the ssh options from the command and its arguments. This is useful when you have arguments that start with a hyphen (-), as it prevents them from being interpreted as ssh options.

By using this modified ssh command, the remote server will receive the command as:

my_script.sh "arg1" "arg 2"

Now, the script will correctly interpret arg 2 as a single argument with a space.

It's important to note that the ssh command may vary depending on the operating system and shell you are using. The example provided here assumes a Unix-like environment with the Bash shell. If you are using a different shell or operating system, you may need to adjust the command accordingly.

Conclusion

Passing $@ over ssh while accounting for spaces in arguments can be a bit tricky. By enclosing the entire command within single quotes and using double quotes around $@, we can ensure that the remote server receives the command as a single string, preserving the spaces in the arguments. Remember to separate the ssh options from the command and its arguments using -- if necessary.

References

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