IDisposable Thoughts

I don’t know you but I love the Fish shell. Yeah yeah I know, it is not POSIX standard and all those things, but seriously, it is awesome, go, give it a try.

Well, one of the problems you find when you move to Fish is finding good shell scripts, because for most cases Fish syntax is incompatible with ZSH or Bash. Today was one of those days. I wanted to write a simple script to give me the name of the current terminal I was working on, and I find this nice line of code in StackExchange but, well, it is not going to work in Fish:

ps -p $(ps -p $$ -o ppid=) -o args=

First, we need to understand what the script does: $$, which is pretty awesome, returns the PID of the current process (in this case, the terminal process) and well, ps is the standard process status command with arguments to return the process id of its parent. Easy, right?

Well, Fish has no notion of $$, but the equivalent is our friend %self. Another big difference is how to group operations. In Bash you use $(), but in Fish you just use a simple parenthesis. So at the end the equivalent command is just:

ps -p (ps -p %self -o ppid=) -o args=

Nice! Wait… If you run this command in Linux using something like Gnome terminal or Konsole it will work, and it is awesome but guess what, in MacOSX it doesn’t work, it will just return login -fp blah instead of the terminal name… bummer! Well, that is a feature in MacOSX, but luckily you can just query an environment variable, TERM_PROGRAM, and that will give you the answer you are looking for!

Now, we just add a few other things, like removing the application path and extension if present, and voila! there you have the full script! (You can get the script from my Github gist)

function which_term
  switch (ps -p (ps -p %self -o ppid=) -o args=)
  case 'login*'
    echo (basename $TERM_PROGRAM .app)
  case '*'
    echo (basename (ps -p (ps -p %self -o ppid=) -o args=))
  end
end

See? Fish is awesome!