Tuesday, May 04, 2010

Linux: fish: The Friendly, Interactive Shell

I'm trying out a new shell called fish. Here are some screen shots and here is a great article to help you get started.

Usually, I'm a zsh user. fish aims to be as powerful as, say, zsh, but a heck of a lot easier to use and a lot easier to learn. So far, that's proven true. The shell provides intelligent tab completion, syntax highlighting, helpful error reporting, integrated documentation, etc.

Fish is inspired by Bourne shell syntax, but is not compatible with it. Specifically, a lot of ugly things have been cleaned up and made more regular. I do think that the syntax is nicer, although it takes a while to get the hang of if you're already a shell expert. About the only inconvenient part of switching to fish is that I can no longer copy and paste complicated bash one-liners from various places online.

The documentation is excellent. However, you might find this cheat sheet helpful for getting started:
: Get help with using fish.
Searching through history:
: Type in the search string, and press the up arrow.
: Open a file using the proper application.
if true; echo hello; end
for i in a b c; echo $i; end
switch $you; case '*'; echo hi; end
function hi; echo hello; end
rm $file:
: You don't have to quote $file, even if it has spaces.
: Double quotes do variable substitution. Single quotes don't.
: Nesting doubles in singles or singles in doubles doesn't hurt
: anything. Both forms allow a minimal escaping, such as \', \\,
: or \$.
set smurf blue
: This is variable assignment. They didn't use the "=" syntax
: because in fish, *everything* is a command. Use -e to erase a
: variable, -l to set a variable locally, -g to set a variable
: globally, and -u to set a variable universally. Setting a
: variable universally applies to all fish sessions and will
: even survive a reboot. Use -x when setting a variable to export
: the value of that variable. It is convention that exported
: variables are in uppercase and unexported variables are in
: lowercase.
echo (ls)
: Use parenthesis for subshells.
f1; and f2
: This is like f1 && f2 in bash.
ls **.as
: Find all the .as files recursively.
: Redirect standard error to a file. ^^ is used for appending to
: a file.
function ll; ls -l $argv; end
: This is the replacement for aliasing and "$@".
: This is $! in bash.
: This is the directory for all your functions. They must use a
: .fish extension.
echo input.{c,h,txt}
: Echoes: input.c input.h input.txt
echo {$USER}meister
for i in (seq 10); echo $i; end
: Counts to 10. Actually, so does "seq 10" ;)
set my_array a b c; echo $my_array[1]
: Prints "a". Note, arrays are 1-based, just like seq.
count $my_array
: Returns the number of items in the array.
for i in (seq (count $my_array)); echo $my_array[$i]; end
: Here's how to loop over an array.
for i in $PATH; echo $i; end
: This is the easier way to loop over an array.
The startup file is ~/.config/fish/config.fish.
: Quickly lists the current directory, or the directory your
: cursor is over.
: Adds "| less". Think "pager".
Fish supports even more Emacs-like commands--even a killring.


Kenny said...

Thanks, mate.

I really think Bash is ugly. It's even uglier to write scripts longer than 50 lines. I'd rather use something Python, Perl or Ruby for such scripts.

Now Fish looks really... delicious. :-)

Thanks, for writing about it.

Shannon -jj Behrens said...

I still prefer Python or Ruby for long scripts, but sometimes, a short shell script really hits the spot ;)

Yes, Fish's syntax does look and feel nice.

Yassen said...

I toyed with it a bit. Very nice ideas went into that one but there are a few things that make it clumsier than BASH in places where it really matters:
- typing expr, test -lt, -ge and so on like crazy is no fun at all. BASH addressed this with $(( )) and [[ ]]
- getting the return code of the last command in BASH is as easy as $?. Here I have to type $status and subtract 128 if needed
- I write a cool script and send it to a friend "oh yeah, by the way install fish to run it"

The last point could be addressed by writing a program to do the translation but the other two make me not like it so much as to invest that time.