An Awk Implementation in C99

https://www.raygard.net/awkdoc/

by asicsp • 2 years ago

107 17 2 years ago

riedel• 2 years ago

Always good to see some love for the awk language. I, however l,went down the rabbit hole to find out about toybox and some background. Came back just puzzled (260 slides of slidedeck only for the message that it has a more permissive licence).

mananaysiempre2• 2 years ago

It’s also less of a grab-bag of random imported software than busybox, the tools are mostly written in a single style with some care taken to use the common library. (Making one utility smaller and making the whole multicall binary smaller are different goals.) The advantage is there’s much less redundant or disproportinately oversized stuff. The disadvantage is that most things need to be written anew, so there’s less stuff in general. (In particular, the author has spent a lot of time writing a shell and it’s still not ready).

throw0101b• 2 years ago

The second edition of The AWK Programming Language by Aho, Kernighan, and Weinberger was just released in February:

* https://awk.dev

ToC and preface of the new edition:

* https://awk.dev/pp1-13.pdf

elvis702• 2 years ago

It was in October or November, I think. The book doesn't add much to the first edition, I was quite deceived.

benhoyt2• 2 years ago

It's a second edition, not a new book -- why did you feel deceived? There's a fair bit of restructuring of the first few chapters, and a whole new chapter on exploratory data analysis (which uses the new CSV support) and a bunch of new stuff about the new Unicode-character support.

Brian_K_White• 2 years ago

2nd Edition != Volume 2

pjungwir• 2 years ago

I just finished reading Kernighan & Pike's The Unix Programming Environment this weekend, and it has a lot of awk. I read it more as a history book (it was published 40 years ago!), but the awk parts were a highlight, second only to the long penultimate chapter building your own calculator/programming language. It kind of made we want to learn more than just the basics I've been using for almost 25 years. But it also recalled Larry Wall's intro in Learning Perl, and how Perl started as a "better awk". That intro is really a direct response to K&P's book I think. So I don't know. I loved Perl in those days, and I agree about how not everything is doable as a shell pipeline. But a second edition makes me want to read it anyway. :-)

abathur• 2 years ago

Oblique, but since this topic might be catnip for people who'd know:

Anyone aware of a Python parser for the Awk language?

I found a number of Awk-alikes implemented in Python, but they all sounded like they took enough liberties that I wouldn't expect them to have a parser worth trying to lean on to parse wild Awk scripts.

nerdponx• 2 years ago

Is there a Tree Sitter grammar for AWK? That could be a good way to go, via the Python bindings for Tree Sitter.

mananaysiempre2• 2 years ago

You would probably get reasonable results from simply feeding the POSIX grammar to lrparsing[1], but unfortunately it doesn’t look like there’s much support in it for lexer feedback (aka the “lexer hack”), which you’ll need for the regular expression syntax. It’s likely possible to hack that in, but I don’t know how much work it’d be.

[1] https://lrparsing.sourceforge.net/

dwheeler• 2 years ago

Cool. Awk is a nice tool for semi-simple record-at-a-time processing.

As far as I can tell, this implementation is much slower than other awks. Most awk implementations use a non-backtracking regex implementation (as do Rust and Go). By contrast, this seems to be using a backtracking implementation (e.g., like Perl and Python). For simplicity that makes sense, but for some regexes this kind of implementation can be many orders of magnitude slower.

My guess is that this slowdown doesn't matter for a typical toybox user, where small code size is valued. Thanks for the link!

shawn_w• 2 years ago

Looks like it uses the standard POSIX regular expression functions - regcomp() and regexec().

UncleEntity• 2 years ago

Do you mean for the parser or the engine that does the awking?

I was looking over the POSIX spec to see what's so difficult about parsing it and just kind of wondering.

anthk2• 2 years ago

You can write a Z-Machine interpreter in awk, a Tetris and with Gawk, even a gopher client.

anthk2• 2 years ago

I have a mirror of an awk-related gopher hole from an awk fan as sadly the former domain it's offline. Here's the github repo, but the author has nice addons such as a universal awk library with missing functions for awk (tan, bitwise ops...) https://git.sr.ht/~luxferre/

Luckly, the AWK library it's used for a project:

https://git.sr.ht/~luxferre/DALE-8A/blob/master/tgl.awk

Also, there's a solitaire written in POSIX AWK:

git://git.luxferre.top/nnfc.git

His homepage:

https://luxferre.top

benhoyt2• 2 years ago

I've chatted with Ray (the author of wak -- love the name) a few times about our respective AWK implementations. He's a nice guy and a really thoughtful programmer, and he even found several edge-case bugs in my GoAWK implementation: https://github.com/search?q=repo%3Abenhoyt%2Fgoawk+raygard&t...

An Awk Implementation in C99

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