fix issues with track_anything.sh

args were broken due to shift and other problems
-1 didn't work because of the subshell
output filtering didn't work with uniq.  this was resolved by adding an
unbuf function which uses stdbuf to fix buffering.

scripts/track_anything.sh

@@ -1,11 +1,12 @@
+# shellcheck shell=bash
+
 export ZERO="$0"
 HELP="$ZERO: tracker [-1] [-v [-v ...]] [q [-q ...]]
   -1     run once and exit
   -v     increase verbosity (default >= warn)
   -q     decrease verbosity
 "
-EXITING=0
+trap 'kill -15 $$' INT
-trap 'EXITING=1' INT
 
 trace() { (( LOG_LEVEL > 2 ))  && (exec 1>&2; builtin echo "$@"|grep .||true); }
 debug() { (( LOG_LEVEL > 1 ))  && (exec 1>&2; builtin echo "$@"|grep .||true); }
@@ -15,6 +16,8 @@ error() { (( LOG_LEVEL > -2 )) && (exec 1>&2; builtin echo "$@"|grep .||true); }
 fatal() {                         (exec 1>&2; builtin echo "$@"|grep .||true); exit 4; }
 log()   { info "$@"; }
 
+unbuf() { SCRIPT="$1"; shift ; stdbuf -oL -eL bash -c "$SCRIPT" - "$@" ; }
+
 start() {
   if ! options="$(getopt vq1 -- "$@")";then
     fatal "$HELP"
@@ -24,17 +27,18 @@ start() {
 
   while [ $# -gt 0 ];do                            
     case "$1" in                                  
-      -1) shift;ONCE=1 ;;
+      -1) ONCE=1 ;;
-      -h) echo "requesting help" ; help; exit 0 ;;
+      -h) info "$HELP"; exit 0 ;;
-      -v) LOG_LEVEL=$(( LOG_LEVEL + 1 )) ;echo increased log level ;;
+      -v) LOG_LEVEL=$(( LOG_LEVEL + 1 )) ;;
       -q) LOG_LEVEL=$(( LOG_LEVEL - 1 )) ;;
       --) shift;break;;  # we're _explicitly_ done with options
+      -*) error "invalid option $1"; fatal "$HELP" ;;
       *) break;;  # we're done with options.   
     esac                                                                       
     shift                                              
   done
 
-  if [ $VALIDATION ];then
+  if [ "$VALIDATION" ];then
     # fix up the validation regex to not search.
     VALIDATION="${VALIDATION#^}"
     VALIDATION="${VALIDATION%'$'}"
@@ -48,36 +52,33 @@ start() {
   debug "POLL_INTERVAL: $POLL_INTERVAL"
   debug "    watch_cmd: $watch_cmd"
 
-  if [ $(echo "$POLL_INTERVAL < $RATE_LIMIT"|bc) -eq 1 ];then
+  if [ "$(echo "$POLL_INTERVAL < $RATE_LIMIT"|bc)" = 1 ];then
     warn "POLL_INTERVAL cannot be less than RATE_LIMIT."
     info "increasing POLL_INTERVAL to $RATE_LIMIT."
     POLL_INTERVAL=$RATE_LIMIT
   fi
 
-  while ! (( EXITING ));do
+  while true;do
-    (
+    _poll || exit $?
-      _poll || exit $?
+    (( ONCE )) && exit 0
-      (( ONCE )) && EXITING=1
 
-      $watch_cmd | while ! (( EXITING ));do
+    $watch_cmd | while sleep $RATE_LIMIT;do
-        sleep $RATE_LIMIT
+      # read with a maximum of the poll interval minus the previous rate limit.
-
+      # rounding _up_ to the nearest second.  (bc floors when scale is unset.)
-        # read with a maximum of the poll interval minus the previous rate limit.
+      if read -r -t "$( echo "$POLL_INTERVAL - $RATE_LIMIT + .5 " | bc )";then
-        # rounding _up_ to the nearest second.  (bc floors when scale is unset.)
+        debug "received poll.  removing other poll requests."
-        if read -t $( echo "$POLL_INTERVAL - $RATE_LIMIT + .5 " | bc );then
+      else
-          debug "received poll.  removing other poll requests."
+        debug "reached the polling interval.  forcing poll."
-        else
+      fi
-          debug "reached the polling interval.  forcing poll."
+      N=0
-        fi
+      while read -t 0;do read -r; N=$((N + 1));done
-        N=0
+      debug "removed $N extra events"
-        while read -t 0;do read; N=$((N + 1));done
+      _poll
-        debug "removed $N extra events"
+      debug "sleeping for $RATE_LIMIT"
-        _poll
+    done
-        debug "sleeping for $RATE_LIMIT"
+    warn "tracker died.  restarting after $RATE_LIMIT seconds."
-      done
+    sleep $RATE_LIMIT
-    ) | eval "$_filter"
+    done | unbuf "$_filter"
-    (( EXITING == 0 )) && (warn "tracker died.  restarting after $RATE_LIMIT seconds.";sleep $RATE_LIMIT)
-  done
   info "bye"
 }
 
@@ -90,10 +91,10 @@ _poll() {
   done
 
   local failed=0
-  if [ $JQ_VALIDATION ];then
+  if [ "$JQ_VALIDATION" ];then
     echo "$NEWVAL" | jq -e "$JQ_VALIDATION" > /dev/null || failed=1
   fi
-  if [ $VALIDATION ];then
+  if [ "$VALIDATION" ];then
     echo "$NEWVAL" | grep -qE "$VALIDATION" || failed=1
   fi
   if (( failed ));then
@@ -115,7 +116,7 @@ poll_interval() {
   POLL_INTERVAL=$1
 }
 
-_filter=uniq
+_filter="uniq"
 filter() {
   _filter="$(printf " %q" "$@")"
 }