Efficient Logging Mechanism in Shell ( log4sh ) [https://www.cubicrace.com/2016/03/efficient-logging-mechnism-in-shell.html]

gistfile1.txt

#!/bin/sh
SCRIPT_LOG=logfile.log

# https://serverfault.com/questions/103501/how-can-i-fully-log-all-bash-scripts-actions
exec 3>&1 4>&2
trap 'exec 2>&4 1>&3' 0 1 2 3
exec 1>$SCRIPT_LOG 2>&1

source ./logger.sh
SCRIPTENTRY
updateUserDetails(){
    ENTRY
    DEBUG "Username: $1, Key: $2"
    INFO "User details updated for $1"
    EXIT
}

INFO "Updating user details..."
updateUserDetails "cubicrace" "3445"

rc=2

if [ ! "$rc" = "0" ]
then
    ERROR "Failed to update user details. RC=$rc"
fi
SCRIPTEXIT

logger.sh

#!/bin/sh

touch $SCRIPT_LOG

function SCRIPTENTRY(){
 timeAndDate=`date`
 script_name=`basename "$0"`
 script_name="${script_name%.*}"
 echo "[$timeAndDate] [DEBUG]  > $script_name $FUNCNAME" >> $SCRIPT_LOG
}

function SCRIPTEXIT(){
 script_name=`basename "$0"`
 script_name="${script_name%.*}"
 echo "[$timeAndDate] [DEBUG]  < $script_name $FUNCNAME" >> $SCRIPT_LOG
}

function ENTRY(){
 local cfn="${FUNCNAME[1]}"
 timeAndDate=`date`
 echo "[$timeAndDate] [DEBUG]  > $cfn $FUNCNAME" >> $SCRIPT_LOG
}

function EXIT(){
 local cfn="${FUNCNAME[1]}"
 timeAndDate=`date`
 echo "[$timeAndDate] [DEBUG]  < $cfn $FUNCNAME" >> $SCRIPT_LOG
}


function INFO(){
 local function_name="${FUNCNAME[1]}"
    local msg="$1"
    timeAndDate=`date`
    echo "[$timeAndDate] [INFO]  $msg" >> $SCRIPT_LOG
}


function DEBUG(){
 local function_name="${FUNCNAME[1]}"
    local msg="$1"
    timeAndDate=`date`
 echo "[$timeAndDate] [DEBUG]  $msg" >> $SCRIPT_LOG
}

function ERROR(){
 local function_name="${FUNCNAME[1]}"
    local msg="$1"
    timeAndDate=`date`
    echo "[$timeAndDate] [ERROR]  $msg" >> $SCRIPT_LOG
}