Hacker News

While sometimes a plausible explanation for huge differences in search time, there are at least two other possible explanations.

First is parallelism. If you do `grep -r`, most greps (like GNU grep and BSD grep and the one found on macOS) will not use parallelism. ripgrep will. This could easily account for a large perceived difference in search time.

Second is the grep implementation. While GNU grep is generally considered to be quite fast on its own (especially in the POSIX locale), many other grep implementations are not. And indeed, they may be extraordinarily slow. For example, consider this comparison between FreeBSD grep (on macOS) and ripgrep (I clipped the `time` output for the `wc -l` command, which I just used to make the output smaller):

    $ time rg -j1 -uuu -w -g '*.c' '[A-Z]{2}_RESUME' | wc -l
          22

    real    0.769
    user    0.105
    sys     0.662
    maxmem  5104 MB
    faults  0


    $ time LC_ALL=C grep -E -w -r --include '*.c' '[A-Z]{2}_RESUME' | wc -l
          22

    real    15.830
    user    14.576
    sys     1.253
    maxmem  2224 MB
    faults  1

    $ time LC_ALL=C ggrep -E -w -r --include '*.c' '[A-Z]{2}_RESUME' | wc -l
          22

    real    1.148
    user    0.206
    sys     0.767
    maxmem  2784 MB
    faults  1

This is just a straight up comparison that removes things like parallelism and filtering completely. This is purely algorithms. And the difference is an order of magnitude.

Any one of these explanations, on its own, can account for huge differences in perceived performance. It's not really possible to know which one (perhaps even all 3) is relevant from pithy descriptions of ripgrep being so much faster than other tools.

Version info for above commands:

    $ rg --version
    ripgrep 14.1.1 (rev bb88a1ac45)

    features:+pcre2
    simd(compile):+NEON
    simd(runtime):+NEON

    PCRE2 10.45 is available (JIT is available)

    $ grep -V
    grep (BSD grep, GNU compatible) 2.6.0-FreeBSD

    $ ggrep -V
    ggrep (GNU grep) 3.12
    Packaged by Homebrew
    Copyright (C) 2025 Free Software Foundation, Inc.
    [.. snip ..]