5 ms·

It would actually be interesting to see how much faster dash is than everything else.

by chasil 2y ago

throwaway2037 2y ago
Why is Dash frequently touted as so much faster than Bash? What is different?
- tzot 2y ago
  It is much simpler (and therefore less resource-hungry) than bash.
- chasil 2y ago
  On rhel9, this is a list of my installed shells. You might notice that dash is smaller than ls (and the rest of the shells). $ ll /bin/bash /bin/dash /bin/ksh93 /bin/ls /bin/mksh -rwxr-xr-x. 1 root root 1389064 May 1 00:59 /bin/bash -rwxr-xr-x. 1 root root 128608 May 9 2023 /bin/dash -rwxr-xr-x. 1 root root 1414912 Apr 9 07:26 /bin/ksh93 -rwxr-xr-x. 1 root root 140920 Apr 8 08:20 /bin/ls -rwxr-xr-x. 1 root root 325208 Jan 9 2022 /bin/mksh $ rpm -qi dash | tail -4 Description : DASH is a POSIX-compliant implementation of /bin/sh that aims to be as small as possible. It does this without sacrificing speed where possible. In fact, it is significantly faster than bash (the GNU Bourne-Again SHell) for most tasks.
laurenth 2y ago
From our experience, ksh is generally faster, and dash sits between ksh and bash. One reason is that dash stores variables using a very small hash table with only 37 entries[0] meaning variable access quickly becomes linear as memory usage grows. But even with that, dash is still surprisingly fast -- when compiling `pnut.c` with `pnut.sh`, dash comes in second place: ksh93: 31s dash: 1m06s bash: 1m19s zsh: >15m [0]: https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/var.c#n66 https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/... EDIT: ksh93, not ksh
- AdmiralAsshat 2y ago
  People still use KornShell?
  - chasil 2y ago
    All of Android is still based on a pdksh-derivative known as mksh, which is an enormous install base. http://www.mirbsd.org/mksh.htm http://www.mirbsd.org/mksh.htm OpenBSD switched their default shell to their own pdksh-derivative known as oksh. https://github.com/ibara/oksh https://github.com/ibara/oksh There was an effort to (re)start ksh93 development, but AT&T halted this effort. The bugfixes from the failed effort have moved back into Korn's last release. https://github.com/ksh93/ksh/tree/dev https://github.com/ksh93/ksh/tree/dev
- cb321 2y ago
  For me `dash` compiles in just a few seconds. If you link to a 1-line problem (here, #define VTABSIZE 39), then why not boost that to 79 or 113, say, re-compile the shell and re-run your benchmark? Might lead to a change in upstream that could benefit everyone.
  - chasil 2y ago
    Or rework the array so realloc() can expand its size?
    - cb321 2y ago
      Yes.. Another fine idea, just more work than a 2 character edit. :-)

It would actually be interesting to see how much faster dash is than everything else.

by chasil 2y ago

It would actually be interesting to see how much faster dash is than everything else.

throwaway2037 2y ago

Why is Dash frequently touted as so much faster than Bash? What is different?

tzot 2y ago
It is much simpler (and therefore less resource-hungry) than bash.
chasil 2y ago
On rhel9, this is a list of my installed shells. You might notice that dash is smaller than ls (and the rest of the shells). $ ll /bin/bash /bin/dash /bin/ksh93 /bin/ls /bin/mksh -rwxr-xr-x. 1 root root 1389064 May 1 00:59 /bin/bash -rwxr-xr-x. 1 root root 128608 May 9 2023 /bin/dash -rwxr-xr-x. 1 root root 1414912 Apr 9 07:26 /bin/ksh93 -rwxr-xr-x. 1 root root 140920 Apr 8 08:20 /bin/ls -rwxr-xr-x. 1 root root 325208 Jan 9 2022 /bin/mksh $ rpm -qi dash | tail -4 Description : DASH is a POSIX-compliant implementation of /bin/sh that aims to be as small as possible. It does this without sacrificing speed where possible. In fact, it is significantly faster than bash (the GNU Bourne-Again SHell) for most tasks.

laurenth 2y ago

From our experience, ksh is generally faster, and dash sits between ksh and bash. One reason is that dash stores variables using a very small hash table with only 37 entries[0] meaning variable access quickly becomes linear as memory usage grows. But even with that, dash is still surprisingly fast -- when compiling `pnut.c` with `pnut.sh`, dash comes in second place: ksh93: 31s dash: 1m06s bash: 1m19s zsh: >15m [0]: https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/var.c#n66 https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/... EDIT: ksh93, not ksh

AdmiralAsshat 2y ago
People still use KornShell?
- chasil 2y ago
  All of Android is still based on a pdksh-derivative known as mksh, which is an enormous install base. http://www.mirbsd.org/mksh.htm http://www.mirbsd.org/mksh.htm OpenBSD switched their default shell to their own pdksh-derivative known as oksh. https://github.com/ibara/oksh https://github.com/ibara/oksh There was an effort to (re)start ksh93 development, but AT&T halted this effort. The bugfixes from the failed effort have moved back into Korn's last release. https://github.com/ksh93/ksh/tree/dev https://github.com/ksh93/ksh/tree/dev
cb321 2y ago
For me `dash` compiles in just a few seconds. If you link to a 1-line problem (here, #define VTABSIZE 39), then why not boost that to 79 or 113, say, re-compile the shell and re-run your benchmark? Might lead to a change in upstream that could benefit everyone.
- chasil 2y ago
  Or rework the array so realloc() can expand its size?
  - cb321 2y ago
    Yes.. Another fine idea, just more work than a 2 character edit. :-)