Plan 9: A variant of the Look command of acme, reverse/case-insensitive/etc options

Looki

#!/bin/rc
# A variant of the Look command of acme.
# Usage: Looki [-r] [-s] [-w] [-x] [SEARCH]
#	-r: search backwards
#	-s: case sensitive
#	-w: whole words
#	-x: regex mode, only makes sense when giving explicit param
# Flags may be combined, as in: -rws
#
# This is not an acme builtin: if invoked with an explicit
# param (as opposed to using the selection or 2-1 chording) it is 
# necessary to quote characters that may be interpreted by rc, eg
# instead of `Looki ^` do `Looki '^'`. 
#
# Bugs:
# - Spaces at beginning/end are ignored; cant' have more than 1
#   consecutive spaces.
#
# test: blah Blah blahx Blahx
# test: x $y^$* ab("cd\n") \n t..t:
# test: x $y^$* ab("cd\n") \n t..t:
# Test: X $Y^$* AB("cd\N") \N T..T:

rfork e
flag e +

fn log{
	echo $* >[1=2] >/dev/null
}

fn decase{
	echo $* | awk '{
		res = ""
		n = split($0, chars, "");
		for(i=1; i <= n; i++) {
			c = chars[i]
			if(match(c, /[A-Za-z]/))
				res = res "[" toupper(c) tolower(c) "]"
			else
				res = res c
		}
		printf("%s\n", res)
	}'
}

fn escape{
	echo $* | sed 's/[.\?\*\+\|\^\$\[\]\(\)\\]/\\&/g'
}

reverse=n
sensitive=n
word=n
regex=n
while(~ $1 -*){
	if(~ $1 *r*) reverse=y
	if(~ $1 *s*) sensitive=y
	if(~ $1 *w*) word=y
	if(~ $1 *x*) regex=y
	shift
}

w=/mnt/acme/$winid
<$w/addr >$w/ctl {
	if(~ $#* 0){
		echo 'addr=dot'
		sel=`{cat $w/xdata}
	}
	if not sel=$"*
	if(~ $sel '') exit ''

	if(~ $regex n) sel=`{escape $sel}
	if(~ $sensitive y) rx=$sel
	if not rx=`{decase $"sel}
	rx=$"rx
	oldrx=$rx
	if(~ $word y) rx='(^|[^A-Za-z_])' ^ $rx ^ '($|[^A-Za-z_])'
	deslashed=`{echo $rx | sed 's,/,\\/,g'}
	cmd='/' ^ $"deslashed ^ '/'
	if(~ $reverse y) cmd='-' ^ $cmd

	log cmd: $cmd
	echo 'addr=dot'
	if(echo -n $cmd >$w/addr >[2]/dev/null){
		if(~ $word y)
			# shrink selection back to original
			echo -n '.-#0/' ^ $oldrx >$w/addr
		echo 'dot=addr'
		echo show
	}
}
exit ''