#!/bin/rc
# watch
#   -c: don't clear between updates
#   -e: exit on command error
#   -t: don't show title date and time
#   -m: set maximum number of lines to show
#   -n: set interval in seconds (may be floating point)
rfork e

flagfmt='c,e,t,m maxlines,n interval'
args='cmd [arg ...]'

fn usage{
	aux/usage
	exit usage
}
fn isfloat{
	echo $1 | grep -s '^[0-9\.]+$'
}
fn isnum{
	echo $1 | grep -s '^[0-9]+$'
}
fn clear{
	awk 'END { for(i = 0; i < '$len'; i++) printf "\x08" }' </dev/null
}
fn output{
	if(~ $#flagt 0)
		echo $title
	echo -n $out
}

if(! ifs=() eval `{aux/getflags $*} || ~ $#* 0)
	usage
cmd=$*
int=2
if(~ $#flagn 1){
	if(! isfloat $flagn)
		usage
	int=$flagn
}
if(~ $#flagm 1){
	if(! isnum $flagm)
		usage
	cmd=($cmd '|' sed $flagm^q)
}
out=()
len=()
stat=''
oifs=$ifs

while(){
	if(~ $#flagt 0)
		title=`{date}
	ifs=()
	out=`{eval $cmd >[2=1]}
	stat=$status
	ifs=$oifs
	if(~ $#flagc 0 && ~ $#len 1)
		clear
	len=`{output | wc -r}
	output
	if(~ $flage 1 && ! ~ $stat ''){
		echo status'='$"stat
		exit $"stat
	}
	sleep $int
}