Simple script for checking time interval when MacOS' display has turned on and off. This is intended to be used for tracking work hours.

get-work-hours.bash

#!/usr/bin/env bash

# A script for checking when MacOS has been in use.
# This script is meant for tracking work hours.
# Script checks when display has been turned on and off and calculates time difference.
# Result is given in format HH:MM:SS, that's the time difference between first display on
# and last display off log messages.
#
# The script is using only one log file (one day) at a time, so working overnight and then checking
# hours won't probably give meaningful result.

# Show parameter (which log file has been read) or instructions how to run the script.
if [ "$1" != "" ]; then
    echo "Parameter is:"
    echo $1
else
    echo "Parameter is empty. Run the script by:"
    echo "    script_name logfile"
    echo "For example:"
    echo "    $0 /var/log/powermanagement/2019.10.16.asl all"
    exit 1
fi

# If parameter all has been given, print all display on/off entries.
if [ "$2" = "all" ]; then
    echo "Parameter all was given, printing all display on/off log entries:"
    syslog -f $1 2>/dev/null | grep -i display
fi

# 2>/dev/null is for supperssing "NOTE:  Most system logs have moved to a new logging system.  See log(1) for more information."
time_stamps=$(syslog -f $1 2>/dev/null | grep -i display | sed -e 1b -e '$!d')

# If no display on/off time stamps has been found from the log file, print "no work",
# else calculate working hours.
if [ -z "$time_stamps" ]
then
    echo "No work done on $1"
else
    echo "Time stamps when laptop display has been turned on and off:"
    syslog -f $1 2>/dev/null | grep -i display | sed -e 1b -e '$!d'
    
    start_secs=$(date -j -f '%H:%M:%S' $(syslog -f $1 2>/dev/null | grep -i display | head -1 | tr -s ' ' | cut -d' ' -f 3) '+%s')
    stop_secs=$(date -j -f '%H:%M:%S' $(syslog -f $1 2>/dev/null | grep -i display | tail -1 | tr -s ' ' | cut -d' ' -f 3) '+%s')
    working_hours=$(($stop_secs-$start_secs))
        
    date -u -r $working_hours '+%H:%M:%S'
fi