Help with regex matching syntax

[thivmcthiv]

Hello, I'm new to this crate entirely, and I'm trying to figure out how to use the grep crate to find matches of words like this (with * representing any number of characters):
with a slice like this:

 const WORDLIST: &'static [u8] = b"\n word\n book\n sphinx\n someotherword\n"; ```

and then a search function like this:
```rust
fn search(pattern: &str, wordlist: &'static [u8]) -> Result<(), Box<Error>> {
    let matcher = RegexMatcher::new_line_matcher(pattern)?;
    let mut matches: Vec<(u64, String)> = vec![];
    Searcher::new().search_slice(&matcher, wordlist, UTF8(|lnum, line| {
        // We are guaranteed to find a match, so the unwrap is OK.
        let mymatch = matcher.find(line.as_bytes())?.unwrap();
        matches.push((lnum, line[mymatch].to_string()));
        Ok(true)
    }))?;
    println!("matches:{:?}", matches);
    Ok(())
}

And I want to be able to use a pattern like this s*nx where the * would represent any number of characters, so one of the matches with search( *s*nx, WORDLIST) would be the word sphinx.
I'm not sure how to do this with regex syntax, and I took a look at https://docs.rs/regex/1.4.2/regex/#syntax but I am a huge beginner and couldn't figure it out. Any help would be greatly appreciated.

[BurntSushi]

Note: I edited your comment to use backticks instead of double quotes around your regexes. Without those, the * characters are usually interpreted as Markdown, which means it's rendered in a way you don't expect.

Note: I converted this to a discussion question since it seems more like a support question rather than a bug report or a feature request.

As for your question, it looks like you're asking for help with constructing the regex itself? And not the actual code? If so, you're pretty close. The * itself is a unary operator, meaning that it takes a single argument. In regex syntax, the * applies to the "thing" preceding it. In your case, s*nx, the * applies to the s, which modifies it to mean, "match the letter s zero or more times." Here are some other examples:

• ab*c, the * applies to b only.
• (ab)*c, the * applies to ab, and says, "match zero or more occurrences of of ab."

If you're used to globs, then this syntax is different. In globs, * is not an operator but a wildcard itself. The regex equivalent of it is more like, .*, which says, "match any character zero or more times." In regex syntax, the . is a wildcard meaning, "match any character."

So in your case, it sounds like you want s.*nx instead of s*nx.

[thivmcthiv]

Ah, ok. That makes sense. So potentially I could also do something like this: [a-z]* if I wanted to match one or more of any character between a and z.

…

On Sun, Dec 6, 2020 at 5:30 AM Andrew Gallant ***@***.***> wrote: Note: I edited your comment to use backticks instead of double quotes around your regexes. Without those, the * characters are usually interpreted as Markdown, which means it's rendered in a way you don't expect. Note: I converted this to a discussion question since it seems more like a support question rather than a bug report or a feature request. As for your question, it looks like you're asking for help with constructing the regex itself? And not the actual code? If so, you're pretty close. The * itself is a *unary operator*, meaning that it takes a single argument. In regex syntax, the * applies to the "thing" preceding it. In your case, s*nx, the * applies to the s, which modifies it to mean, "match the letter s zero or more times." Here are some other examples: - ab*c, the * applies to b only. - (ab)*c, the * applies to ab, and says, "match zero or more occurrences of of ab." If you're used to globs, then this syntax is different. In globs, * is not an operator but a wildcard itself. The regex equivalent of it is more like, .*, which says, "match any character zero or more times." In regex syntax, the . is a wildcard meaning, "match any character." So in your case, it *sounds* like you want s.*nx instead of s*nx. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1753 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ALTRKROT65JCZ7UDVMO2KKTSTN2OTANCNFSM4UPJD4FA> .

[BurntSushi]

Yes. I might suggest looking at a few regex tutorials to get your bearings. I don't have any particular one to recommend though unfortunately.

[thivmcthiv]

Alrighty, thanks for the help.

…

On Mon, Dec 7, 2020 at 11:37 AM Andrew Gallant ***@***.***> wrote: Yes. I might suggest looking at a few regex tutorials to get your bearings. I don't have any particular one to recommend though unfortunately. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1753 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ALTRKRKB23QPGKXJD6A7NC3STUOHFANCNFSM4UPJD4FA> .