monitor_nchan: fix incorrect PID reference in pkill / pgrep

sbin/monitor_nchan

@@ -5,6 +5,7 @@ disk_load=/var/local/emhttp/diskload.ini             # disk load statistics
 nginx=/var/run/nginx.socket                          # nginx local access
 status=http://localhost/pub/session?buffer_length=1  # nchan information about GUI subscribers
 nchan_list=/tmp/nchan_list.tmp
+pid_file=/var/run/monitor_nchan.pid
 nchan_id=$(basename "$0")
 
 nchan_subs(){
@@ -24,17 +25,19 @@ nchan_idle(){
 
 nchan_stop() {
   echo -n >$nchan_list
+  pid=$(cat $pid_file)
   while IFS=$'\n' read -r nchan; do
     [[ ${nchan##*/} == '.*' ]] && continue
     echo $nchan >>$nchan_list
-    pkill --ns $$ -f $nchan
+    pkill --ns $pid -f $nchan
   done <<< $(ps -eo cmd | grep -Po '/usr/local/emhttp/.*/nchan/.*')
 }
 
 nchan_start() {
   [[ -e $nchan_list ]] || return
+  pid=$(cat $pid_file)
   while IFS=$'\n' read -r nchan; do
-    if ! pgrep --ns $$ -f $nchan >/dev/null; then
+    if ! pgrep --ns $pid -f $nchan >/dev/null; then
       $nchan &>/dev/null &
     fi
   done < $nchan_list
@@ -78,4 +81,5 @@ while :; do
   fi
   # check every 30 seconds
   sleep 30
-done &
+done & echo $! >$pid_file
+