Combining functions in Fish

Question

In Fish shell I have two functions:

function be
  bundle exec $argv
end

function rdbm
  rake db:migrate
end

I typically use them together, i.e. bundle exec rake db:migrate but not always, so I'd like to keep them separate.

The problem is that I cannot do this with the aliases I have currently defined:

To say be rdbm expands the first function (be) but passes rdbm as a literal string (non-expanded).

I have also tried abbr:

abbr be 'bundle exec'
abbr rdbm 'rake db:migrate'

But only the first expands.

I've figured out that it's possible to call functions from other functions:

function be_rdbm
  echo (be rake db:migrate)
end

but this doesn't decouple the two functions, since the second is not being used.

By the way, I'd like to know if that last example can be improved. I don't see why the echo should be necessary (or what alternatives there are), but I cannot put the parenthesis as the entire content of the function.

Answer 1

Personally I would just define another abbreviation for the combined case. However, you can define your rdbms function as follows to allow you to combine it with your be function as be (rdbm):

function rdbm
    if status --is-command-substitution
        echo rake db:migrate
    else
        rake db:migrate
    end
end

You could also modify your be function so that you can type just type be rdbm when used with the previous change:

function be
    if test "$argv" = "rdbm"
        bundle exec (rdbm)
    else
        bundle exec $argv
    end
end

Answer 2

zsh has a "global alias" feature, where the alias is substituted anywhere in the line. But fish only substitutes the first word in the command line.

You could do this:

function rdbm
  if [ (count $argv) = 1 ]; and [ $argv[1] = "-n" ]
    echo "rake db:migrate"
  else
    rake db:migrate
  end
end

Then you would have to type

be (rdbm -n)