When running the following command:
docker-machine ssh name-here "docker swarm init --advertise-addr $(hostname -I | awk '{print $1}')"
I get the following error:
hostname: illegal option -- I usage: hostname [-fs] [name-of-host]
This is because the command is attempting to run hostname -I on my local machine, running on MacOS, which doesn't have a -I flag.
Attempting to run without double quotes gives the same error.
I encapsulated the full command in double quotes so my expectation would be that the full contents of the double quotes is executed as a single argument to docker-machine ssh, but it seems that this is not the case.
I've tried single quotes (') but this interferes with awk's single quote requirement around the print. I even tried the crazy $$ as you would use in makefiles next to the hostname but this doesn't work either.
Why is $(hostname -I | awk '{print $1}') being executed on the host machine when the command is encapsulated in double quotes, and how can I run the above command correctly to initialise a docker swarm with the hostname within the machine?
According to man bash:
Enclosing characters in double quotes preserves the literal value of all characters within the quotes, with the exception of $,
, \, and, when history expansion is enabled, !. The characters $ andretain their special meaning within double quotes. The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or . A double quote may be quoted within double quotes by preceding it with a backslash. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using a backslash. The backslash preceding the ! is not removed.
So with this in mind, the following works:
docker-machine ssh name-here 'docker swarm init --advertise-addr $(hostname -I | awk '\'{print \$1}\'')'
Note how the $1 in print is escaped with a \, and one set of single quotes are also escaped around print.