Bash script to list opened files when lsof command not available

lsof.sh

#!/usr/bin/env bash

declare -a SEARCH_PATHS
SEARCH_PATHS[1]=/proc/*
PROC_INDEX=1

while [[ $# -gt 1 ]]; do
    case "${1}" in
        -p | --pid) SEARCH_PATHS[$PROC_INDEX]="/proc/${2}"; PROC_INDEX=$((PROC_INDEX + 1)); shift 2 ;;
        *) ;;
    esac
done

# function dirname() { echo "${1%/*}" }
# function basename() { echo "${1##*/}" }


function lsof_main() {
    # /proc/2277/fd/8
    printf "%6s %-50s %8s %s\n" PID EXECUTABLE FD FILE
    for fd_path in $(find ${SEARCH_PATHS[@]} -path '*/fd/*' -maxdepth 2 2>/dev/null |sort -V); do
        fd_num="${fd_path##*/}"
        proc_dir="${fd_path%/*/*}"
        if [[ "${proc_dir}" != "${last_proc_dir}" ]]; then
            proc_pid="${proc_dir##*/}"
            proc_exe="$(readlink ${proc_dir}/exe)"

            last_proc_dir="${proc_dir}"
        fi

        fd_link="$(readlink ${fd_path} 2>/dev/null)"

        if [[ -n "${fd_link}" ]]; then
            printf "%6s %-50s %8s %s\n" "${proc_pid}" "${proc_exe}" "${fd_num}" "${fd_link}"
        fi
    done
}

2>/dev/null lsof_main