url_encode() {
  sed '
    s/%/%25/g
    s/ /%20/g
    s/!/%21/g
    s/"/%22/g
    s/#/%23/g
    s/\$/%24/g
    s/\&/%26/g
    s/'\''/%27/g
    s/(/%28/g
    s/)/%29/g
    s/\*/%2a/g
    s/+/%2b/g
    s/,/%2c/g
    s/-/%2d/g
    s/\./%2e/g
    s/\//%2f/g
    s/:/%3a/g
    s/;/%3b/g
    s//%3e/g
    s/?/%3f/g
    s/@/%40/g
    s/\[/%5b/g
    s/\\/%5c/g
    s/\]/%5d/g
    s/\^/%5e/g
    s/_/%5f/g
    s/`/%60/g
    s/{/%7b/g
    s/|/%7c/g
    s/}/%7d/g
    s/~/%7e/g
  '
}