Inotifywait for doing batch file processing

script.sh

#!/bin/bash

# This script is supposed to show the usage of inotifywait when you want process
# files in a directory in batches once the files have been created.
# 
#
# Test this script with:
#
#      $ this-script.sh
#      $ for i in a b c ; do echo $i > /tmp/$i.profraw; done \
#          && sleep 2 \
#          && for i in d e f g; do echo $i > /tmp/$i.profraw; done \
#          && sleep 2 \
#          && echo "" > /tmp/shutdown
#
# You should see an output like this:
#
#     Processing batch (size: 3) in 5 seconds: 
#     a.profraw
#     b.profraw
#     c.profraw
#     DONE
#     Processing batch (size: 4) in 5 seconds: 
#     d.profraw
#     e.profraw
#     f.profraw
#     g.profraw
#     DONE
#
# Notice that the first batch has the minimal size (3) and that the second batch
# has size (4) because the /tmp/g.profraw file is created while the main script
# is still processing the first batch. This proofs that queing up events like
# this does work.

# The directory in which to search for files
directory=/tmp
# Regex for the files to look out for
files_regex='.*\.profraw$'
# Number of files that have to exist before we're processing them.
min_batch_size=3
# This file acts as to queue up file paths that we want to work on.
batch_file=/tmp/batch.txt
# Once the number of lines in the batch_file reach the min_batch_size we move
# the content of batch_file over to this file and then processing can happen
# while batch_file can collect more files.
batch_file_in_process=/tmp/batch_in_process.txt
# Once there's a write event to this file, the program exits gracefully.
shutdown_file=/tmp/shutdown

# Empty batch_file (if exists) or create batch file.
function empty_batch_file() {
    truncate -s 0 $batch_file
}

empty_batch_file

# On every *.profraw file written to in the /tmp directory,
# write an event line to list of files to process in a batch.
nohup inotifywait -q -m -o $batch_file -e close_write \
    --format '%f' \
    --include $files_regex \
    $directory > /dev/null 2>&1 &
background_monitor_pid=$!
trap 'kill -s KILL $background_monitor_pid' EXIT

# Observe if a new profile was added to the list of the current batch.
# If the shutdown file was modified, gracefully shutdown.
inotifywait -q -m -e modify \
    --include "($(basename $batch_file)|$(basename $shutdown_file))" \
    $directory \
| while read -r directory event filename
do
    if [ "$filename" = "$(basename $shutdown_file)" ]; then
        echo "Exiting gracefully..."
        exit 0
    fi
    batch_size=$(wc -l < $batch_file)
    if [ $batch_size -le 0 ]; then
        # This event happens when we empty the batch file
        continue
    fi
    if [ $batch_size -lt $min_batch_size ]; then
        echo "Batch is still too small: $batch_size must be at least $min_batch_size"
        continue
    fi
    cat $batch_file > $batch_file_in_process
    empty_batch_file
    echo "Processing batch (size: $batch_size) in 5 seconds: "
    cat $batch_file_in_process
    sleep 5 # <----- Do your actual work here
    echo "DONE"
    rm -fv $(cat $batch_file_in_process)
done