# Created on savesnippets.com · https://savesnippets.com/ALOOF5iTxpc5Rj
trim() {
    local s="$*"
    # Strip leading whitespace
    s="${s#"${s%%[![:space:]]*}"}"
    # Strip trailing whitespace
    s="${s%"${s##*[![:space:]]}"}"
    printf '%s' "$s"
}

trim "   hello world   "          # "hello world"
trim $'\t\n  spaces  \n\t'         # "spaces"