3 ms·

So, I found this very interesting to read. I created an empty file, a la the original true, named truth and placed it at the beginning of my $PATH. $ time

by greggyb 12y ago

So, I found this very interesting to read. I created an empty file, a la the original true, named truth and placed it at the beginning of my $PATH. $ time truth real 0m0.002s user 0m0.000s sys 0m0.003s I then realized that since true is a builtin, I'd need to call the true binary with its full path. I'd hate to give one an unfair advantage by having to search the path vs being called by name. So.... $ time /usr/bin/true real 0m0.001s user 0m0.000s sys 0m0.000s $ time /usr/local/sbin/truth real 0m0.003s user 0m0.000s sys 0m0.000s $ time true # The builtin real 0m0.000s user 0m0.000s sys 0m0.000s Clearly my 2KB true binary is superior to an empty file. The builtin (obviously) outperforms both, by at least one order of magnitude (estimated). This post is not intended to be a serious performance comparison.

function_seven 12y ago
I just repeated your test, but got opposite results: $ time /usr/bin/true real 0m0.003s user 0m0.001s sys 0m0.002s $ time /usr/bin/truth real 0m0.001s user 0m0.000s sys 0m0.001s I can't imagine for the life of me how an empty file could perform worse than an actual binary, but there's gotta be a reason.
- cpwright 12y ago
  If you're relying on an empty binary, or exit 0; instead of an actual binary you have to execute a shell process to evaluate it. The binary doesn't need to load a shell, it can just do a bit of setup, then make a single exit 0 system call.
  - function_seven 12y ago
    Thank you. That makes sense. So basically the empty file is seen by the shell as a "script" that has to be evaluated, so a separate shell process is spun up to handle it? And the difference between my output and the parent's has to do with some difference in our environments?
- logicallee 12y ago
  this is what happens when we aren't allowed to use p values anymore :) https://www.sciencebasedmedicine.org/psychology-journal-bans-significance-testing/ https://www.sciencebasedmedicine.org/psychology-journal-bans... The default p is p = 0.5, so I have no trouble accepting both your conclusion and your parent's :) seriously though, this is why we use significance testing in real fields, like computer science...
  - greggyb 12y ago
    Exactly. I did the most naive thing possible and only once for each version of true/truth. I was just bored/curious.

by greggyb 12y ago

function_seven 12y ago

I just repeated your test, but got opposite results: $ time /usr/bin/true real 0m0.003s user 0m0.001s sys 0m0.002s $ time /usr/bin/truth real 0m0.001s user 0m0.000s sys 0m0.001s I can't imagine for the life of me how an empty file could perform worse than an actual binary, but there's gotta be a reason.

cpwright 12y ago
If you're relying on an empty binary, or exit 0; instead of an actual binary you have to execute a shell process to evaluate it. The binary doesn't need to load a shell, it can just do a bit of setup, then make a single exit 0 system call.
- function_seven 12y ago
  Thank you. That makes sense. So basically the empty file is seen by the shell as a "script" that has to be evaluated, so a separate shell process is spun up to handle it? And the difference between my output and the parent's has to do with some difference in our environments?
logicallee 12y ago
this is what happens when we aren't allowed to use p values anymore :) https://www.sciencebasedmedicine.org/psychology-journal-bans-significance-testing/ https://www.sciencebasedmedicine.org/psychology-journal-bans... The default p is p = 0.5, so I have no trouble accepting both your conclusion and your parent's :) seriously though, this is why we use significance testing in real fields, like computer science...
- greggyb 12y ago
  Exactly. I did the most naive thing possible and only once for each version of true/truth. I was just bored/curious.