9 Jul
2018
9 Jul
'18
5:27 a.m.
On Jul 8, 2018, at 1:50 PM, Perry E. Metzger <perry(a)piermont.com> wrote:
On Thu, 5 Jul 2018 15:56:50 +1000 Warren Toomey <wkt(a)tuhs.org> wrote:
I believe autocompletion has been available for 20+ years. IIRC, I
switched to zsh in 1995 and it has had autocompletion then. But you
do have to teach zsh/bash how to autocomplete for a given program.
For instance
compctl -K listsysctls sysctl
listsysctls() { set -A reply $(sysctl -AN ${1%.*}) }
The compctl tells the shell what keyword list to use (lowercase k)
or command to use to generate such a list (uppercase K). Then the
command has to figure out how to generate such a list given a prefix.
This sort of magic incantation is needed because no one has bothered
to create a simple library for autocompletion & no standard convention
has sprung up that a program can use. It is not entirely trivial but
not difficult either. Cisco's CLI is a great model for this. It would
even prompt you with a help string for non-keyword args such as ip
address or host! With Ciscso CLI ^D to list choices, ^I to try auto
complete and ? to provide context sensitive help. It was even better
in that you can get away with just typing a unique prefix. No need to
hit <tab>. Very handy for interactive use.
OK, I guess I'll be the one to start things
going on the COFF list.
What other features, ideas etc. were available in other operating
systems which Unix should have picked up but didn't?
[ Yes, I know, it's on-topic for TUHS but I doubt it will be for
long! ]
A minor feature that I might mention: TOPS-20 CMND JSYS style command
completion. TL;DR, this feature could now be implemented, as after
decades of wanting it I finally know how to do it in a unixy way.
In TOPS-20, any time you were at the EXEC (the equivalent of the
shell), you could hit "?" and the thing would tell you what options
there were for the next thing you could type, and you could hit ESC to
complete the current thing. This was Very Very Nice, as flags and
options to programs were all easily discoverable and you had a handy
reminder mechanism when you forgot what you wanted.
bash has some vague lame equivalents of this (it will complete
filenames if you hit tab etc.), and if you write special scripts you
can add domain knowledge into bash of particular programs to allow for
special application-specific completion, but overall it's kind of lame.
Here's the Correct Way to implement this: have programs implement a
special flag that allows them to tell the shell how to do completion
for them! I got this idea from this feature being hacked in, in an ad
hoc way, into clang:
http://blog.llvm.org/2017/09/clang-bash-better-auto-completion-is.html
but it is apparent that with a bit of work, one could standardize such
a feature and allow nearly any program to provide the shell with such
information, which would be very cool. Best of all, it's still unixy
in spirit (IMHO).