But seriously, although echo is typically a shell built-in and distinctly faster than /usr/bin/echo, it’s still much slower than <<<, presumably because it still has to set up a pipe and an extra… shall we say pseudoprocess.

Comparing behaviours for feeding text into `true` (typically a shell built-in, so that process spawn times doesn’t drown the signal):

  try() {
      echo -e "\e[32;1m$1\e[m"
      for (( run = 0; run < 5; run++ )); do
          time (for (( i = 0; i < 1000; i++ )); do
              $2
          done)
      done
  }

  a() { /usr/bin/echo .dump | true; }; try /usr/bin/echo a
  b() {          echo .dump | true; }; try echo          b
  c() {            <<<.dump   true; }; try '<<<'         c
  d() {                       true; }; try "no piping"   d

• /usr/bin/echo: 750μs/845μs

• echo: 469μs/371μs

• <<<: 11μs/31μs

• No piping: 3μs/10μs

So… yeah, on a very slightly older or slower machine than mine, using <<< may save you more than half a millisecond. That’s a much bigger difference than I expected—I was expecting it to be well under 200μs, maybe under 100μs, though the more I think about it the more I realise my expectation may have been unreasonable.