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by chasil 698 days ago
It would actually be interesting to see how much faster dash is than everything else.
2 comments
laurenth 698 days 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/...

EDIT: ksh93, not ksh

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cb321 698 days 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.
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chasil 698 days ago
Or rework the array so realloc() can expand its size?
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cb321 698 days ago
Yes.. Another fine idea, just more work than a 2 character edit. :-)
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AdmiralAsshat 698 days ago
People still use KornShell?
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chasil 698 days 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

OpenBSD switched their default shell to their own pdksh-derivative known as 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

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throwaway2037 698 days ago
Why is Dash frequently touted as so much faster than Bash? What is different?
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chasil 698 days 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.
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tzot 698 days ago
It is much simpler (and therefore less resource-hungry) than bash.
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