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Comment by dTal | Hacker News Reader

You might also add that it's actually impossible to implement cd as a standalone tool - processes cannot change their parent's working directory.

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It's not pretty, but you can: https://rudd-o.com/linux-and-free-software/the-shell-challen...

Well how about that. Serve me right calling something "impossible".

Now what do I say? "Impossible without awful hackery"?

Are other commands also different from shell to shell? It seems like an interesting point, if true.

Here's a couple of pages listing the builtins in bash: https://www.gnu.org/software/bash/manual/html_node/Shell-Bui...

And zsh: http://zsh.sourceforge.net/Doc/Release/Shell-Builtin-Command...

Powershell doesn't really have "builtins" per-se, every cmdlet is executed in the process of the shell itself but they're all contained within loadable modules (though 2-3 modules are loaded with the shell startup by default), Invoke-WebRequest is contained within Microsoft.PowerShell.Utility for example.

Lots of simple shell functionality is provided as builtins. See the bash manual for a list of builtins inherited from the Bourne Shell[1] and that are bash-specific[2].

Note that some of these are part of the POSIX standard, so there's not a huge amount of variance allowed between shells which are being compliant. Obviously, PowerShell doesn't adhere to this.

[1] https://www.gnu.org/software/bash/manual/html_node/Bourne-Sh...

[2]: https://www.gnu.org/software/bash/manual/html_node/Bash-Buil...

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