Default bash script in strict mode

strict_bash.sh

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

# Run this script with bash -x (script name) to execute commands one a time
# while IFS=' ', read -r col1 col2 col3 col4 col5; do echo "I got: $col1 | $col2"; done < authors.csv
# while IFS=' ', read LINE; do echo $LINE | cut -f 2; done < authors.csv
#/ Usage: ./process_authors.sh -p migration-support/authors.tsv -s '' 
#/ 
#/ Description: Transform authors.xml into TSV and then 
#/      import into a WordPress installation. This scripts expects to be
#/      run from the root of a WordPress installation and requires all
#/      supporting scripts be located in a folder called 
#/      "migration-support" in the same directory. All parameters are
#/      required even though they may be empty strings ('').
#/ Examples: (same as usage above)
#/ Options:
#/   --help: Display this help message
#/   -p|--path_to_input_xml: path to the TSV file 
#/   -s|--site: the URL of the multisite being updated, empty string if
#/          not a multisite installation
usage() { grep '^#/' "$0" | cut -c4- ; exit 0 ; }
expr "$*" : ".*--help" > /dev/null && usage

# get the named parameters
while [ "${1:-}" != "" ]; do
    case $1 in
        -p | --path_to_a_file)      shift
                                    path_to_input_xml=${1:-}
                                    ;;
        -s | --additional_input)    shift
                                    additional_input=${1:-}
                                    ;;
        -h | --help )               usage
                                    exit
                                    ;;
        * )                         usage
                                    exit 1
    esac
    shift
done

# tiny logging framework, logs have datetime stamps
DATEFILE='%Y%m%d%H%M%S'
DATESTAMP='%Y-%m-%d %H:%M:%S'
mkdir -p 'logs'
readonly LOG_FILE="logs/$(basename "$0")-$(basename "$path_to_input_xml").log"
echo '' > "$LOG_FILE"
info()    { echo "[INFO]    $$ $*" | tee -a "$LOG_FILE" >&2 ; }
warning() { echo "[WARNING] $$ $*" | tee -a "$LOG_FILE" >&2 ; }
error()   { echo "[ERROR]   $$ $*" | tee -a "$LOG_FILE" >&2 ; }
fatal()   { echo "[FATAL]   $$ $*" | tee -a "$LOG_FILE" >&2 ; exit 1 ; }

# what to do when the script is interrupted, Ctrl+C, for example
function cleanup() { 
    # Restart services
    echo "Cleaning up $$"
    exit 0
}

# traps commands that exit with an error status
function onerror_handler() {
    MYLINE=$1
    error "An error occurred on line $MYLINE."
    exit 127
}

# and finally, the actual script
if [[ "${BASH_SOURCE[0]}" = "$0" ]]; then

    # Trap Ctrl+C and respond accordingly
    trap 'cleanup $LINENO' INT

    # Trap an error in the code and respond accordingly
    trap 'onerror_handler $LINENO' ERR

    # Rest of script goes here

fi
exit 0