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Pnut: A C to POSIX shell compiler you can trust

pnut.sh

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Re: Pnut: A C to POSIX shell compiler you can trust

#11

Post by marcodiego »

forrestthewoods wrote: post #7

Hrmmm. But why? Quite frankly I think Bash scripting is awful and frequently wish shell scripts were written in a real and debuggable language. For anything non-trivial that is. I feel like I’d rather write C and compile it with Cosmopolitan C to give me a cross-platform binary than this. Neat project. Definitely clever. But it’s headed in the opposite direction from what I’d prefer...

Master Foo once said to a visiting programmer: “There is more Unix-nature in one line of shell script than there is in ten thousand lines of C.”

The programmer, who was very proud of his mastery of C, said: “How can this be? C is the language in which the very kernel of Unix is implemented!”

Master Foo replied: “That is so. Nevertheless, there is more Unix-nature in one line of shell script than there is in ten thousand lines of C.”

The programmer grew distressed. “But through the C language we experience the enlightenment of the Patriarch Ritchie! We become as one with the operating system and the machine, reaping matchless performance!”

Master Foo replied: “All that you say is true. But there is still more Unix-nature in one line of shell script than there is in ten thousand lines of C.”

The programmer scoffed at Master Foo and rose to depart. But Master Foo nodded to his student Nubi, who wrote a line of shell script on a nearby whiteboard, and said: “Master programmer, consider this pipeline. Implemented in pure C, would it not span ten thousand lines?”

The programmer muttered through his beard, contemplating what Nubi had written. Finally he agreed that it was so.

“And how many hours would you require to implement and debug that C program?” asked Nubi.

“Many,” admitted the visiting programmer. “But only a fool would spend the time to do that when so many more worthy tasks await him.”

“And who better understands the Unix-nature?” Master Foo asked. “Is it he who writes the ten thousand lines, or he who, perceiving the emptiness of the task, gains merit by not coding?”

Upon hearing this, the programmer was enlightened.

Re: Pnut: A C to POSIX shell compiler you can trust

#12

Post by luism6n »

forrestthewoods wrote: post #7

Hrmmm. But why? Quite frankly I think Bash scripting is awful and frequently wish shell scripts were written in a real and debuggable language. For anything non-trivial that is. I feel like I’d rather write C and compile it with Cosmopolitan C to give me a cross-platform binary than this. Neat project. Definitely clever. But it’s headed in the opposite direction from what I’d prefer...

I'm not the OP, but I think the goal is to make it cross architecture. Cross platform C compiler would give you cross OS compatibility, but chip architecture would still be fixed, I think.

I.e., you can take your compiled.sh and run in an obscure processor with an obscure OS, as long as it's POSIX, it should work...

Re: Pnut: A C to POSIX shell compiler you can trust

#13

Post by forrestthewoods »

marcodiego wrote: post #11
forrestthewoods wrote: post #7

Hrmmm. But why? Quite frankly I think Bash scripting is awful and frequently wish shell scripts were written in a real and debuggable language. For anything non-trivial that is. I feel like I’d rather write C and compile it with Cosmopolitan C to give me a cross-platform binary than this. Neat project. Definitely clever. But it’s headed in the opposite direction from what I’d prefer...

Master Foo once said to a visiting programmer: “There is more Unix-nature in one line of shell script than there is in ten thousand lines of C.” The programmer, who was very proud of his mastery of C, said: “How can this be? C is the language in which the very kernel of Unix is implemented!” Master Foo replied: “That is so. Nevertheless, there is more Unix-nature in one line of shell script than there is in ten thous…

And then the programmer had to debug a hundred line shell script and they realized it should have all been written in Python or Rust instead.

Master Foo is shorthand for Fool.

Re: Pnut: A C to POSIX shell compiler you can trust

#14

Post by wahern »

This is very cool, regardless of how serious it was intended to be taken. Before base-64 encoders/decoders became more common as preinstalled commands in the environments I found myself on, I wrote a base64 utility in mostly pure POSIX shell:

  https://25thandClement.com/~william/2023/base64.sh
If this project had existed I might have opted to compile my C-based base-64 encoder and decoder routines, suitably tweaked for pnut's limitations.

I say base64.sh is mostly pure not because it relies on shell extensions, but because the only non-builtins it depends on are od(1) or, alternatively, dd(1) to assist with binary I/O. And preferably od(1), as reading certain control characters, like NUL, into a shell variable is especially dubious. The encoder is designed to operate on a stream of decimal encoded bytes. (See decimals_fast for using od to encode stdin to decimals, and decimals_slow for using dd for the same.)

It looks like pnut uses `read -r` for reading input. In addition to NULs and related raw byte issues, I was worried about chunking issues (e.g. truncation or errors) on binary data, e.g. no newlines within LINE_BUF bytes. Have you tested binary I/O much? Relatedly, how many different shell implementations have you tested your core scheme with? In addition to bash, dash, and various incarnations of /bin/sh on the BSDs, I also tested base64.sh with Solaris' system shells (ksh88 and ksh93 derivatives), as well as AIX's (ksh88 derivative). AIX had some odd quirks with pipelines even with plain text I/O. (Unfortunately Polar Home is gone, now, so I have no easy way to play with AIX; maybe that's for the better.)

Re: Pnut: A C to POSIX shell compiler you can trust

#15

Post by jcranmer »

andrewf wrote: post #8

Looking forward to the point where this can build autoconf. It's great that the generated ./configure script is portable but if I want to make substantial changes to the project I need to find a binary for my machine (and version differences can be quite substantial)

> Looking forward to the point where this can build autoconf.

Autoconf is a perl program that turns (heavily customized) m4 files into shell scripts. How does a C compiler help there?

Re: Pnut: A C to POSIX shell compiler you can trust

#16

Post by donatj »

marcodiego wrote: post #11
forrestthewoods wrote: post #7

Hrmmm. But why? Quite frankly I think Bash scripting is awful and frequently wish shell scripts were written in a real and debuggable language. For anything non-trivial that is. I feel like I’d rather write C and compile it with Cosmopolitan C to give me a cross-platform binary than this. Neat project. Definitely clever. But it’s headed in the opposite direction from what I’d prefer...

Master Foo once said to a visiting programmer: “There is more Unix-nature in one line of shell script than there is in ten thousand lines of C.” The programmer, who was very proud of his mastery of C, said: “How can this be? C is the language in which the very kernel of Unix is implemented!” Master Foo replied: “That is so. Nevertheless, there is more Unix-nature in one line of shell script than there is in ten thous…

I was going to cite this on reading the parent comment after reading it. Was very glad to see you beat me to it!

Re: Pnut: A C to POSIX shell compiler you can trust

#17

Post by VitoVan »

marcodiego wrote: post #11
forrestthewoods wrote: post #7

Hrmmm. But why? Quite frankly I think Bash scripting is awful and frequently wish shell scripts were written in a real and debuggable language. For anything non-trivial that is. I feel like I’d rather write C and compile it with Cosmopolitan C to give me a cross-platform binary than this. Neat project. Definitely clever. But it’s headed in the opposite direction from what I’d prefer...

Master Foo once said to a visiting programmer: “There is more Unix-nature in one line of shell script than there is in ten thousand lines of C.” The programmer, who was very proud of his mastery of C, said: “How can this be? C is the language in which the very kernel of Unix is implemented!” Master Foo replied: “That is so. Nevertheless, there is more Unix-nature in one line of shell script than there is in ten thous…

http://catb.org/~esr/writings/unix-koans/ten-thousand.html

Re: Pnut: A C to POSIX shell compiler you can trust

#19

Post by theamk »

If you are wondering how it handles C-only functions.. it does not.

open(..., O_RDWR | O_EXCL) -> runtime error, "echo "Unknow file mode" ; exit 1"

lseek(fd, 1, SEEK_HOLE); -> invalid code (uses undefined _lseek)

socket(AF_UNIX, SOCK_STREAM, 0); -> same (uses undefined _socket)

looking closer at "cp" and "cat" examples, write() call does not handle errors at all. Forget about partial writes, it does not even return -1 on failures.

"Compiler you can Trust", indeed... maybe you can trust it to get all the details wrong?

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