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Comment by steveklabnik | Hacker News Reader

> Why is reading lines from a file so hard?

It's not so much that it's hard, as is there's lots of options. Can you afford to read it all into memory as a String? Do you need to only read it bit by bit?

> Why is it my job to tell it how to buffer?

Systems langauges need to expose these kinds of details and levels of control.

> Nobody is going to know how to do this

I googled "rust open a file and read by lines" and got these results:

https://users.rust-lang.org/t/read-a-file-line-by-line/1585

https://doc.rust-lang.org/std/io/

https://doc.rust-lang.org/std/fs/struct.File.html

The first two show you directly how, though the first one is dealing with the error message. The last one shows reading it all in. I have some more work to do :)

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It would be silly and wasteful to read the whole file into memory just so I can iterate its lines. I'm not sure why that's an option you'd need to accomodate.

However, many languages make a reasonable assumption that you can afford to fit each line in memory, and provide an obvious way to do this.

> I'm not sure why that's an option you'd need to accomodate.

Again, it's about control. Maybe you're only loading a small configuration file, and so fetching it all in one go is better than dealing with a buffer.

> an obvious way to do this.

If you search for 'line' or 'lines' in rustdoc, the correct thing is right near the top, which will show you how to use it with BufRead.

> Maybe you're only loading a small configuration file, and so fetching it all in one go is better than dealing with a buffer.

If it's small, it can't be that much worse to buffer. What's wrong with reasonable defaults?

Can you tell me what it means to search for 'line' or 'lines' in rustdoc? Is this a command-line tool? I'm aware of the 'rustdoc' that generates documentation, but not of anything by that name that searches documentation, and Googling isn't turning up much of anything except the Rust book here.

It would be great to have an offline way to search Rust documentation and examples, as things like this make it very hard to write Rust on a plane, for example.

Googling often gives answers that are wrong or pre-1.0. You seem to have better luck at searching for the right things, perhaps because you are an expert in the language and know exactly what to search for.

(Amusing related anecdote: I googled for "how to return self in rust" and got a suicide prevention website. Jeez, Google, it's not that bad.)

> Can you tell me what it means to search for 'line' or 'lines' in rustdoc?

Rustdoc has a search bar at the top. with 'line' it's the third result, 'lines' is the first https://doc.rust-lang.org/stable/std/?search=lines

and the short description makes it clear that the first two results are irrelevant in this case.

> It would be great to have an offline way to search Rust documentation and examples,

It all works offline. These docs are pre-installed for you when you install Rust, and 'cargo doc' will generate them for your whole project.

> perhaps because you are an expert in the language and know exactly what to search for.

I copy-pasted my search term exactly in the previous post.

> Rustdoc has a search bar at the top.

Let me assure you that I mean only the best for this language and I appreciate your persistent willingness to help, but I want to help debug your use of internal terminology that doesn't help beginners.

"rustdoc" is not how you should be telling beginners to look for documentation. As far as I can tell, "rustdoc" is the tool for generating documentation, not searching it. I assume you use rustdoc a lot and that's why the name comes to mind.

Maybe the term is overloaded, but I cannot find anything called "rustdoc" that involves a search bar. Googling for "rustdoc" gives many forms of Rust documentation, none of which have a search bar. DuckDuckGo-ing for "rustdoc" (as some documentation suggests instead of Googling) gets me some of the same things, plus rustdoc.com, which is a big honking security warning on top of someone's broken personal blog.

I know that exact link you gave me includes a search bar, but that's an example of finding the answer because you already know it.

And if you know to go to doc.rust-lang.org and go to the Standard Library API Reference, you get a search bar, but that's not where I would think of going to answer the question "how do I iterate lines".

That's why I end up Googling and getting to Stack Overflow, full of wrong answers and someone named Shepmaster yelling at newbies.

As I said in the other thread, I truly appreciate it. :)

Sorry, as I mentioned elsewhere I was in a meeting; I should have just waited to apply to you. It's true that "rustdoc" is overloaded, people use it to mean "rustdoc's output" which would mean the standard library docs in this case. My bad!

o/ waves

Please make sure to leave a comment and/or downvote any answers that are wrong to help people coming after you. I also apologize for whichever specific way I harmed you.

> It would be great to have an offline way to search Rust documentation and examples,

>> It all works offline. These docs are pre-installed for you when you install Rust, and 'cargo doc' will generate them for your whole project.

Not by default, anymore[0], as I found out when I wanted to read the book offline.

To set up offline documentation, do:

  rustup component add rust-docs # One-time thing

Now to open the docs in a browser, do one of:

  rustup doc
  rustup doc --api
  rustup doc --book

The second and third forms open up the API documentation and the book, respectively. Bookmark for one-click access.

[0] https://users.rust-lang.org/t/psa-rust-documentation-is-now-...

Gah, I always forget. I want that switched back.

> I copy-pasted my search term exactly in the previous post.

I'm bringing up a problem with how the language presents itself to beginners, not asking you to solve a specific problem for me. If searching is the answer to everything, then there needs to be a concerted effort to take Google-juice away from bad or deprecated answers.

Incidentally, the search result you're describing for "lines" says "An iterator over the lines of an instance of BufRead.", which only appears to be the answer to "how do I iterate lines of a file?" if you already know what the answer is.

No no, I very much appreciate it!

I think we have two searches confused. When I meant "my exact query, when we were taking about Google, here: https://news.ycombinator.com/item?id=13585902

I find it interesting that we got different results.

I thought "an iterator over lines" would be enough; maybe not.

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