Rust dasturlash tili

Environment(atrof-muhit) o'zgaruvchilari bilan ishlash

Biz minigrepni qo‘shimcha xususiyatni qo‘shish orqali yaxshilaymiz: foydalanuvchi environment orqali yoqishi mumkin bo‘lgan katta-kichik harflarni hisobga olmay qidirish imkoniyati.Biz bu xususiyatni buyruq qatori opsiyasiga aylantirishimiz va foydalanuvchilar uni har safar qo‘llashni xohlaganlarida kiritishlarini talab qilishimiz mumkin, lekin buning oʻrniga uni environment qilib, biz foydalanuvchilarga environmentni bir marta oʻrnatish va barcha qidiruvlarini terminal sessiyasida katta-kichik harflarga sezgir boʻlmasligiga ruxsat beramiz.

Katta-kichik harflarni sezmaydigan qidiruv funksiyasi uchun muvaffaqiyatsiz test yozish

Biz birinchi navbatda yangi harflarga_etiborsiz_qidirish funksiyasini qo'shamiz, u muhit o'zgaruvchisi qiymatga ega bo'lganda chaqiriladi. Biz TDD jarayonini kuzatishda davom etamiz, shuning uchun birinchi qadam yana muvaffaqiyatsiz testni yozishdir. Biz yangi harflarga_etiborsiz_qidirish funksiyasi uchun yangi test qo‘shamiz va 12-20 ro‘yxatda ko‘rsatilganidek, ikkita test o‘rtasidagi farqlarni aniqlashtirish uchun eski testimiz nomini birinchi_natija harflarga_etiborliga o‘zgartiramiz.

Fayl nomi: src/lib.rs

use std::error::Error;
use std::fs;

pub struct Config {
    pub sorov : String,
    pub fayl_yoli: String,
}

impl Config {
    pub fn build(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("argumentlar yetarli emas");
        }

        let sorov  = args[1].clone();
        let fayl_yoli = args[2].clone();

        Ok(Config { sorov , fayl_yoli })
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let tarkib = fs::read_to_string(config.fayl_yoli)?;

    for line in qidiruv(&config.sorov , &tarkib) {
        println!("{line}");
    }

    Ok(())
}

pub fn qidiruv<'a>(sorov : &str, tarkib: &'a str) -> Vec<&'a str> {
    let mut natijalar = Vec::new();

    for line in tarkib.lines() {
        if line.contains(sorov ) {
            natijalar.push(line);
        }
    }

    natijalar
}


#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn harflarga_etiborli() {
        let sorov  = "marali";
        let tarkib = "\
Rust:
xavfsiz, tez, samarali.
Uchtasini tanlang.
Duct tape.";

        assert_eq!(vec!["xavfsiz, tez, samarali."], qidiruv(sorov , tarkib));
    }

    #[test]
    fn harflarga_etiborsiz() {
        let sorov  = "rUsT";
        let tarkib = "\
Rust:
xavfsiz, tez, samarali.
Uchtasini tanlang.
Menga ishoning.";

        assert_eq!(
            vec!["Rust:", "Menga ishoning."],
            harflarga_etiborsiz_qidirish(sorov , tarkib)
        );
    }
}

Ro'yxat 12-20: Biz qo'shmoqchi bo'lgan katta-kichik harflarni sezgir bo'lmagan funksiya uchun yangi muvaffaqiyatsiz test qo'shish

Note that we’ve edited the old test’s contents too. We’ve added a new line with the text "Duct tape." using a capital D that shouldn’t match the query "duct" when we’re searching in a case-sensitive manner. Changing the old test in this way helps ensure that we don’t accidentally break the case-sensitive search functionality that we’ve already implemented. This test should pass now and should continue to pass as we work on the case-insensitive search.

The new test for the case-insensitive search uses "rUsT" as its query. In the search_case_insensitive function we’re about to add, the query "rUsT" should match the line containing "Rust:" with a capital R and match the line "Trust me." even though both have different casing from the query. This is our failing test, and it will fail to compile because we haven’t yet defined the search_case_insensitive function. Feel free to add a skeleton implementation that always returns an empty vector, similar to the way we did for the search function in Listing 12-16 to see the test compile and fail.

Implementing the search_case_insensitive Function

The search_case_insensitive function, shown in Listing 12-21, will be almost the same as the search function. The only difference is that we’ll lowercase the query and each line so whatever the case of the input arguments, they’ll be the same case when we check whether the line contains the query.

Filename: src/lib.rs

use std::error::Error;
use std::fs;

pub struct Config {
    pub query: String,
    pub file_path: String,
}

impl Config {
    pub fn build(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let file_path = args[2].clone();

        Ok(Config { query, file_path })
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.file_path)?;

    for line in search(&config.query, &contents) {
        println!("{line}");
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(
    query: &str,
    contents: &'a str,
) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }

    results
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

        assert_eq!(
            vec!["Rust:", "Trust me."],
            search_case_insensitive(query, contents)
        );
    }
}

Listing 12-21: Defining the search_case_insensitive function to lowercase the query and the line before comparing them

First, we lowercase the query string and store it in a shadowed variable with the same name. Calling to_lowercase on the query is necessary so no matter whether the user’s query is "rust", "RUST", "Rust", or "rUsT", we’ll treat the query as if it were "rust" and be insensitive to the case. While to_lowercase will handle basic Unicode, it won’t be 100% accurate. If we were writing a real application, we’d want to do a bit more work here, but this section is about environment variables, not Unicode, so we’ll leave it at that here.

Note that query is now a String rather than a string slice, because calling to_lowercase creates new data rather than referencing existing data. Say the query is "rUsT", as an example: that string slice doesn’t contain a lowercase u or t for us to use, so we have to allocate a new String containing "rust". When we pass query as an argument to the contains method now, we need to add an ampersand because the signature of contains is defined to take a string slice.

Next, we add a call to to_lowercase on each line to lowercase all characters. Now that we’ve converted line and query to lowercase, we’ll find matches no matter what the case of the query is.

Let’s see if this implementation passes the tests:

$ cargo test
   Compiling minigrep v0.1.0 (file:///projects/minigrep)
    Finished test [unoptimized + debuginfo] target(s) in 1.33s
     Running unittests src/lib.rs (target/debug/deps/minigrep-9cd200e5fac0fc94)

running 2 tests
test tests::case_insensitive ... ok
test tests::case_sensitive ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

     Running unittests src/main.rs (target/debug/deps/minigrep-9cd200e5fac0fc94)

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests minigrep

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Great! They passed. Now, let’s call the new search_case_insensitive function from the run function. First, we’ll add a configuration option to the Config struct to switch between case-sensitive and case-insensitive search. Adding this field will cause compiler errors because we aren’t initializing this field anywhere yet:

Filename: src/lib.rs

use std::error::Error;
use std::fs;

pub struct Config {
    pub query: String,
    pub file_path: String,
    pub ignore_case: bool,
}

impl Config {
    pub fn build(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let file_path = args[2].clone();

        Ok(Config { query, file_path })
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.file_path)?;

    let results = if config.ignore_case {
        search_case_insensitive(&config.query, &contents)
    } else {
        search(&config.query, &contents)
    };

    for line in results {
        println!("{line}");
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(
    query: &str,
    contents: &'a str,
) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }

    results
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

        assert_eq!(
            vec!["Rust:", "Trust me."],
            search_case_insensitive(query, contents)
        );
    }
}

We added the ignore_case field that holds a Boolean. Next, we need the run function to check the ignore_case field’s value and use that to decide whether to call the search function or the search_case_insensitive function, as shown in Listing 12-22. This still won’t compile yet.

Filename: src/lib.rs

use std::error::Error;
use std::fs;

pub struct Config {
    pub query: String,
    pub file_path: String,
    pub ignore_case: bool,
}

impl Config {
    pub fn build(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let file_path = args[2].clone();

        Ok(Config { query, file_path })
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.file_path)?;

    let results = if config.ignore_case {
        search_case_insensitive(&config.query, &contents)
    } else {
        search(&config.query, &contents)
    };

    for line in results {
        println!("{line}");
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(
    query: &str,
    contents: &'a str,
) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }

    results
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

        assert_eq!(
            vec!["Rust:", "Trust me."],
            search_case_insensitive(query, contents)
        );
    }
}

Listing 12-22: Calling either search or search_case_insensitive based on the value in config.ignore_case

Finally, we need to check for the environment variable. The functions for working with environment variables are in the env module in the standard library, so we bring that module into scope at the top of src/lib.rs. Then we’ll use the var function from the env module to check to see if any value has been set for an environment variable named IGNORE_CASE, as shown in Listing 12-23.

Filename: src/lib.rs

use std::env;
// --snip--

use std::error::Error;
use std::fs;

pub struct Config {
    pub query: String,
    pub file_path: String,
    pub ignore_case: bool,
}

impl Config {
    pub fn build(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let file_path = args[2].clone();

        let ignore_case = env::var("IGNORE_CASE").is_ok();

        Ok(Config {
            query,
            file_path,
            ignore_case,
        })
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.file_path)?;

    let results = if config.ignore_case {
        search_case_insensitive(&config.query, &contents)
    } else {
        search(&config.query, &contents)
    };

    for line in results {
        println!("{line}");
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(
    query: &str,
    contents: &'a str,
) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }

    results
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

        assert_eq!(
            vec!["Rust:", "Trust me."],
            search_case_insensitive(query, contents)
        );
    }
}

Listing 12-23: Checking for any value in an environment variable named IGNORE_CASE

Here, we create a new variable ignore_case. To set its value, we call the env::var function and pass it the name of the IGNORE_CASE environment variable. The env::var function returns a Result that will be the successful Ok variant that contains the value of the environment variable if the environment variable is set to any value. It will return the Err variant if the environment variable is not set.

We’re using the is_ok method on the Result to check whether the environment variable is set, which means the program should do a case-insensitive search. If the IGNORE_CASE environment variable isn’t set to anything, is_ok will return false and the program will perform a case-sensitive search. We don’t care about the value of the environment variable, just whether it’s set or unset, so we’re checking is_ok rather than using unwrap, expect, or any of the other methods we’ve seen on Result.

We pass the value in the ignore_case variable to the Config instance so the run function can read that value and decide whether to call search_case_insensitive or search, as we implemented in Listing 12-22.

Let’s give it a try! First, we’ll run our program without the environment variable set and with the query to, which should match any line that contains the word “to” in all lowercase:

$ cargo run -- to poem.txt
   Compiling minigrep v0.1.0 (file:///projects/minigrep)
    Finished dev [unoptimized + debuginfo] target(s) in 0.0s
     Running `target/debug/minigrep to poem.txt`
Are you nobody, too?
How dreary to be somebody!

Looks like that still works! Now, let’s run the program with IGNORE_CASE set to 1 but with the same query to.

$ IGNORE_CASE=1 cargo run -- to poem.txt

If you’re using PowerShell, you will need to set the environment variable and run the program as separate commands:

PS> $Env:IGNORE_CASE=1; cargo run -- to poem.txt

This will make IGNORE_CASE persist for the remainder of your shell session. It can be unset with the Remove-Item cmdlet:

PS> Remove-Item Env:IGNORE_CASE

We should get lines that contain “to” that might have uppercase letters:

Are you nobody, too?
How dreary to be somebody!
To tell your name the livelong day
To an admiring bog!

Excellent, we also got lines containing “To”! Our minigrep program can now do case-insensitive searching controlled by an environment variable. Now you know how to manage options set using either command line arguments or environment variables.

Some programs allow arguments and environment variables for the same configuration. In those cases, the programs decide that one or the other takes precedence. For another exercise on your own, try controlling case sensitivity through either a command line argument or an environment variable. Decide whether the command line argument or the environment variable should take precedence if the program is run with one set to case sensitive and one set to ignore case.

The std::env module contains many more useful features for dealing with environment variables: check out its documentation to see what is available.