https://www.reddit.com/r/bash/comments/65yyom/a_prolog_for_shell_scripts_that_need_to_be_more/

# Reset IFS. Even though ksh doesn't import IFS from the environment,
# $ENV could set it. This uses special bash and ksh93 notation,
# not in POSIX.
IFS=$' \t\n'

# Make sure unalias is not a function, since it's a regular built-in.
# unset is a special built-in, so it will be found before functions.
unset -f unalias

# Unset all aliases and quote unalias so it's not alias-expanded.
\unalias -a

# Make sure command is not a function, since it's a regular built-in.
# unset is a special built-in, so it will be found before functions.
unset -f command

# Get a reliable path prefix, handling case where getconf is not
# available.
SYSPATH="$(command -p getconf PATH 2>/dev/null)"
if [[ -z "$SYSPATH" ]]; then
        SYSPATH="/usr/bin:/bin"                 # pick your poison
fi
PATH="$SYSPATH:$PATH"