Question

does anyone know how to lock on a function in bash script?
I wanted to do something like in java (like synchronize), ensuring that each file saved in monitored folder is on hold ever tries to use submit function.

an excerpt from my script:

(...)


ON_EVENT () {
   local date = $1
   local time = $2
   local file = $3
   sleep 5
   echo "$date $time New file created: $file"
   submit $file
}

submit () {
   local file = $1 
   python avsubmit.py -f $file -v
   python dbmgr.py -a $file 
}

if [ ! -e "$FIFO" ]; then 
  mkfifo "$FIFO"
fi

inotifywait -m -e "$EVENTS" --timefmt '%Y-%m-%d %H:%M:%S' --format '%T %f' "$DIR" > "$FIFO" &
INOTIFY_PID=$!

trap "on_exit" 2 3 15

while read date time file
do
  on_event $date $time $file &
done < "$FIFO"

on_exit

I'm using inotify to monitor a folder when a new file is saved. For each file saved (received), submit to VirusTotal service (avsubmit.py) and TreathExpert (dbmgr.py).
Concurrent access would be ideal to avoid blocking every new file created in monitored folder, but lock submit function should be sufficient.

Thank you guys!

Answer 1

Something like this should work:

if (set -o noclobber; echo "$$" > "$lockfile") 2> /dev/null; then
   trap 'rm -f "$lockfile"; exit $?' INT TERM EXIT
   # Your code here
   rm -f "$lockfile"
   trap - INT TERM EXIT
else
   echo "Failed to acquire $lockfile. Held by $(cat $lockfile)"
fi