command-help

#!/usr/bin/env bash
# catch uninitialized variables
set -u

extract_text ()
{
    awk -v cmd="$cmd" -v regex="^\\\s*$1\\\>" '
        $0 ~ regex{f=2; print; next}
        f==2 && /^\s*--/{f=1; print; next}
        f==2 && cmd=="sed" && /^\s*$/{f=1; print; next}
        (/^\s*$/  || /^\s*-/) && f{exit}
        f' "$file"
}

cmd="$1"
shift
file='/tmp/command_help.txt'

cmd_type=$(type -t "$cmd")
if [[ "$cmd_type" == 'builtin' ]]; then
    help -m "$cmd" > "$file"
elif [[ "$cmd_type" == 'file' ]]; then
    man "$cmd" | col -bx > "$file"
else
    echo "Error: $cmd is not a valid command" 1>&2 && exit 1
fi

awk '/^NAME$/{f=1; next} /^\s*$/ && f{exit} f' "$file"
echo

for arg in "$@" ; do
    if [[ $arg =~ ^-- ]] ; then
        arg_mod="(-[a-zA-Z](\\\s*[^,]*)?,\\\s*)?${arg%%=*}"
        extract_text "$arg_mod"
    elif grep -q "^\s*$arg\b" "$file" ; then
        extract_text "$arg"
    elif grep -q "^\s*-[a-zA-Z],\s*$arg\b" "$file" ; then
        arg_mod="-[a-zA-Z],\\\s*${arg%%=*}"
        extract_text "$arg_mod"
    elif [[ $arg =~ ^-[^-] ]] ; then
        while read -n1 char; do
            extract_text "-$char"
            echo
        done < <(echo -n "${arg:1}")
    else
        grep -iw -C3 "$arg" "$file"
    fi
done

rm "$file"