first working try, takes 6 seconds for 10e7 entries

.gitignore

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+measurements
+
+# Added by cargo
+
+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "onebrc-rust"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "onebrc-rust"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

bench.ps1

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+cargo build
+Measure-Command {start-process target/debug/onebrc-rust.exe measurements/measurements-10e7.txt -Wait}

src/main.rs

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+use std::env;
+use std::fs::File;
+use std::io::BufReader;
+use std::io::prelude::*;
+use std::collections::HashMap;
+
+struct Station {
+    values: Vec<f64>
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let filename = &args[1];
+    println!("{filename}");
+
+    let file = File::open(filename).unwrap();
+
+    let mut buffered_reader = BufReader::with_capacity(1024, file);
+    let mut line = String::new();
+
+    let mut stations = HashMap::<String, Station>::new();
+    stations.reserve(10_000);
+    loop {
+        line.clear();
+        let n = buffered_reader.read_line(&mut line).unwrap();
+        if n == 0 {
+            break;
+        }
+
+        // in a worst case, the last 6 chars in a line are taken up by the temp
+        // ...name;-14.4\n
+        // in a best case, the last 4 chars in a line are taken up by the temp
+        // ...name;9.2\n
+        for i in 5..7 {
+            if line.chars().nth_back(i) == Some(';') {
+                let temp: f64 = line[n - i..n - 1].parse().unwrap();
+                let name = String::from(&line[..n - i - 1]);
+
+                if let Some(station) = stations.get_mut(&name) {
+                    station.values.push(temp);
+                } else {
+                    stations.insert(name, Station { values: vec![temp] });
+                }
+                break;
+            }
+        }
+    }
+
+    let mut stations: Vec<_> = stations.iter().collect();
+    stations.sort_unstable_by(|(n1, _), (n2, _)| n1.cmp(n2));
+    for (name, station) in stations {
+        assert!(!station.values.is_empty());
+        println!("{};{:1};{:1};{:1}", name,
+            station.values.iter().cloned().fold(100., f64::min),
+            station.values.iter().sum::<f64>() / station.values.len() as f64,
+            station.values.iter().cloned().fold(-100., f64::max))
+    }
+}