The SSH command accepts a very useful argument that I think is underused by many devops folks looking to run a quick command and get on with their day.

The output of the synopsis of the SSH command man page (man ssh) ends with:

[[email protected]]hostname [command]

This [command] is the useful bit - you can pop any command you like here, and SSH will connect and authenticate to the server, run the command (directing IO to your client as normal), and then exit. This makes it great for standalone tasks that can just…run, for example:

  • ssh [email protected] df -h - to show the disk usage on a server
  • ssh [email protected] ls -lah - to list the contents of the authenticating user’s home directory
  • ssh [email protected] "cd /u/app && bundle exec rake db:migrate" - to change into a Rails app working directory and run migrations

Taking little shortcuts with common commands like this can seem kind of simple, but I’ve found that the time I save really adds up. You can also make use of the command argument for scripting - for example, to automate updates or provisioning.