LWN: Comments on "Go fish! (developerWorks)"

Some bash enhancements...

Richard_J_Neill — Mon, 08 Dec 2008 13:53:53 +0000

It would be nice to see a few changes in bash for version 4. I'd like to see at least the following:
- syntax highlighting at the bash prompt (not just in editors). This idea is one we should take from fish.
- some sensible string functions with aliases defined so that we can use more familiar constructs eg strlen, rather than ${#string}
- trim() or chomp().
- more array functions, eg array_keys(), and multi-dimensional arrays
- a builtin to do path canonicalisation (like /usr/bin/readlink)
- a way to get variables back from subshells (the converse of EXPORT)[1]
- some hybrid of nullglob and failglob so that a mismatched glob results in null. [2]

I still do a *lot* of programming in bash, and it's pretty good. Just not perfect.

[1] Yes, I know this is really an OS feature. But still, why shouldn't a parent be allowed to explicitly access variables set in a subshell? This wouldn't be such a problem, except that subshells can only return a 1-byte integer exit value; rather than an array or a string.

[2] This needs some more explanation - here is an example:
mkdir test
cd test
touch a b c d

ls *z
ls: cannot access *z: No such file or directory
#Normally, bash will fail to expand the *z, and will then pass it to
#ls as a literal '*z'.

shopt -s nullglob
ls *z
a b c d
#Bash now treats '*z' as empty, and runs ls with no parameters.

shopt -s failglob
ls *z
bash: no match: *z
#Here, we get no match, but we get an error instead.

What I want is for "ls *z" to be like listing an empty directory. i.e. bash gives ls an explicit argument of NUL.

Go fish! (developerWorks)

dmag — Sat, 06 Dec 2008 16:02:44 +0000

That's exactly why fish is neat. The existing shells are ONLY used because they are ubiquitous. Nobody says "bash is an awesome programming language."

If you use Fish as your shell, then you can also use it to write Fish shell scripts. The "language" around the shell is a lot less arcane and has more conceptual integrity.

That said, I've tried to use fish as my main shell, and failed because it takes a while to learn. I couldn't figure out how to do "(sleep 1h; xmessage time to go) &".

Go fish! (developerWorks)

njs — Fri, 05 Dec 2008 09:42:22 +0000

Very slick indeed, thanks for sharing!

Go fish! (developerWorks)

sitaram — Fri, 05 Dec 2008 03:11:47 +0000

thanks!

I'm a perl guy normally, but I wrote this to show (show off?) a bunch of perl/python/java type kids what plain bash could do...

Go fish! (developerWorks)

nix — Fri, 05 Dec 2008 00:41:39 +0000

Oh, that's very neat. I can think of half a dozen times I've done things
in deeply ugly ways that could have been done like that.

The code's not even contorted to fit: the 'one line at the end where
control sits forever' just falls out of it.

Go fish! (developerWorks)

sitaram — Thu, 04 Dec 2008 16:49:26 +0000

I'll admit exception handling is a little over the top for a shell, but bash has a few tricks up its sleeve too.

What would you say to a job-queuing program whose main "loop" is essentially the single statement "wait", and which did everything else by trapping SIGCHLD? Take a look at http://sitaramc.googlepages.com/queue.sh (but note: I wrote it for a lark and it seemed to work fine in testing but I never actually used it "in production")

not really a name conflict

jengelh — Thu, 04 Dec 2008 11:41:59 +0000

I seem to remember Midnight Commander once upon a time built upon a fish binary to establish its "Shell link" feature.

Go fish! (developerWorks)

JoeBuck — Wed, 03 Dec 2008 23:52:19 +0000

"Stagnation" just means that 10-year-old code still runs. Better to write a new scripting language than to incompatibly change an old one.

Go fish! (developerWorks)

nix — Wed, 03 Dec 2008 23:48:00 +0000

zsh certainly isn't stagnant either. It doesn't roar along with huge
numbers of new features, but it already has so *many* that if it adds many
more the manual will collapse into a black hole.

(Recentish features include UTF-8 support, which now seems to have enough
of the bugs worked out of it to be useful, and exception handling, which
in any shell but zsh would have me spluttering in amazement. This being
zsh, though, it's not surprising: I fully expect I've just overlooked the
strong AI that can write your code for you, if you can figure out the
incredibly baroque syntax for telling it what to do.)

Go fish! (developerWorks)

drag — Wed, 03 Dec 2008 23:16:42 +0000

I don't see mature and useful software as stagnating. Instead it just gets incorporated into larger and more complex hunks of software.

It's nice to see some change going on though.

not really a name conflict

JoeBuck — Wed, 03 Dec 2008 22:57:14 +0000

... since fish in the context of FTP over SSH is not typed as a command, rather it is used in URLs, always followed by a colon.

Go fish! (developerWorks)

tyhik — Wed, 03 Dec 2008 22:24:47 +0000

> Unix shells have stagnated in recent years.

Like much of that basic unix and internet stuff. The rfc793 dates back to almost thirty years

Go fish! (developerWorks)

tzafrir — Wed, 03 Dec 2008 21:42:46 +0000

On a zsh:

% gpg --l[tab][tab]
--list-keys                                -- list all keys
--list-options                             -- modify what the various --list-*
--list-packets                             -- list only the sequence of packets
--list-public-keys                         -- list all public keys
--list-secret-keys                         -- list all secret keys
--list-sigs                                -- lists keys and signatures
--local-user                               -- use name as the user ID to sign
--lsign-key                                -- sign a key but mark as non-export
--list-only      --lock-never     --logger-fd
--lock-multiple  --lock-once

Go fish! (developerWorks)

emk — Wed, 03 Dec 2008 21:02:26 +0000

Overall, it looks rather nice. There are two things which I would definitely miss, though:

1) "Here documents".
2) The "VAR=value" notation. I've never really loved "set VAR value", personally.

But all in all, it's a good idea. Unix shells have stagnated in recent years.

Go fish! (developerWorks)

jengelh — Wed, 03 Dec 2008 19:09:57 +0000

Hooray again for name conflicts file over ssh (fish) greets.