I like the idea of only having commands, environment variables, pipes,
and conditions (with && and ||). This has some purity, not using the
shell as a programming language, but as a tool to compose other
programs.
I was worried about a few things not being possible at all, like:
find . -type f | xargs md5sum | while read -r hash path
do
cp "$path" "obj/$hash"
done
But then with ...
... | xargs -n 2 cp
... it could work with the odd lines as the sources and even lines as
the destinations:
find . -type f | xargs md5sum |
sed -r 's|([^ ]*) (.*)|\2\nobj/\1|' |
# ./obj/f73696e15dc73e463be705e132df9416
# ./etc/bin/mb-filter
# ./obj/08e1b3a3ff3a4690d651fbbe31b90289
# ./etc/bin/mb-all
# ./obj/4da6918e25e2010cb2612f3378678307
# ./etc/bin/ii-filter
# ...
xargs -n 2 cp
This is still sh(1)-compatible.
Now what if I want to add a condition in-between?
find . -type f | xargs md5sum | while read -r hash path
do
[ -f "obj/$path" ] || cp "$path" "obj/$hash"
done
I could play hard with find:
xargs -I % -n 1 find % -exec test -f {} \; -print
Or I could use non-portable cp -n option which make the test, but
stest(1) is a better approach.
But I have to pipe only the odd lines through it, and keeping the even
lines only if the odd lines did not match.
I could also call s(1) again with xargs, and use another script with
positionnal parameter if s(1) support them (or a -c flag as in sh(1)):
test -f obj/$2 || cp $1 obj/$2
Finally: can it redirect stout to stderr? A stand alone program could
do this:
errout CMD ARGS
So this seems to work. It is possible to reduce shell scripts to mostly
a single pipe for most things. s(1) it then "Just enough". Moreover,
in command-line, I quite never do anything else, so s(1) is perfect for
interactive use for me.
I would still prefer that linenoise was not required, using rlwrap
instead:
rlwrap dash # bonus: rlwrap sic
behaves mostly like bash or other bloated shell.
Thank you for s, it is for me an interesting direction to follow.
rlwrap(1): http://github.com/hanslub42/rlwrap
