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A comment on Sherver: Bash lightweight web server. Parent comment

Re:Sherver: Bash lightweight web server by rascul on Wednesday December 22, 2021 @08:13AM (#29648841)
You had:

    $ strace bash -c 'echo hi' | grep 'exec'
    execve("/usr/bin/bash", ["bash", "-c", "echo hi"], 0x7fffe264aad0 /\* 24 vars */) = 0
Something seems off. strace(1) prints the trace to stderr not stdout, so you should need |& not | to catch it with grep. At least, that's how it works here.

Also, cat does not appear to be inlined for me:

    rascul@smarts:~> strace bash -c 'cat /etc/os-release' |& grep 'exec'
    execve("/usr/bin/bash", ["bash", "-c", "cat /etc/os-release"], 0x7ffe7b5334e0 /* 88 vars */) = 0
    execve("/usr/bin/cat", ["cat", "/etc/os-release"], 0x562c447076f0 /* 88 vars */) = 0*
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Re:Sherver: Bash lightweight web server by junon on Wednesday December 22, 2021 @08:15AM (#29648863)
Yeah good catch, I forgot it since I didn't copy 1:1 the command line into vim when I formatted it for HN. I use fish + powerline so the command line doesn't copy correctly. In fish, it's `&|`, which would look weird anyway. I just forgot to add the `&` after the `|`.

The output was copied 1:1 though.

The inlining is an implementation detail and I've seen it happen differently across different platforms.

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Re:Sherver: Bash lightweight web server by rascul on Wednesday December 22, 2021 @08:21AM (#29648947)
> The inlining is an implementation detail and I've seen it happen differently across different platforms.

Do you have more information on this? I would be interested to read more about it. As far as I was aware (and my knowledge is certainly not exhaustive), the only thing kinda related is as noted in the bash man page:

> The command substitution $(cat file) can be replaced by the equivalent but faster $(< file).

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Re:Sherver: Bash lightweight web server by junon on Wednesday December 22, 2021 @08:26AM (#29648987)
I don't, sorry. I just know it's something some implementations opt-in to (especially drop-in replacements to bash). It's behavior I've observed quite a bit and have leveraged it in some cases to improve the performance of some critical bash scripts over the years. I'd also be interested in some prose about it.
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