[learn rust together] a preliminary understanding of rust package management tool cargo

Tips ： It is suggested to study this chapter after learning the previous section , Please subscribe to this column for details .

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Preface

In the last article we learned Rust Of Hello World, And it is analyzed in detail , I believe you have learned , In this section we will use Cargo Create a Hello World, And analyze it in detail .

We wrote last time Hello World Is the simplest program , There is no dependence . Think , If you are developing a large project , It will definitely reference other libraries , Or manage some files , Build , At this time, compilation becomes a complex problem .Rust The authorities provided it to us Cargo To manage these projects , It can do everything mentioned above , Use Cargo Managing will make your development easier , All we use in our future development are Cargo 了 .

Cargo yes Rust Build system and package manager . majority Rustacean We use it Cargo To manage their Rust project , Because it can handle many tasks for you , Like building code 、 Download dependent libraries and compile them .

Rustacean It refers to the big guy who studies in front of the computer .

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One 、 Use Cargo Create project

First, you need to check whether your computer is installed Cargo, Of course , If you install it normally, it must have been installed .

cargo --version

Go back to , It means there is no problem with the installation , Otherwise, it is recommended that you reinstall Rust.

1. New projects

The following command is used to create a new project

cargo new hello_cargo

among hello_cargo Is the name of the new project , After running, the following figure indicates that the creation is successful .

Next, enter the project directory just created , You can see the directory structure as follows ,

│  .gitignore
│  Cargo.toml
│
└─src
        main.rs

• .gitignore It's a git Ignore file list , Upload to git when , Not all files should be uploaded to github Of . It also reminds us ,cargo For us to create a github Warehouse .
• Cargo.toml It is the configuration file of a project , This includes the project name , Dependency and other contents , Detailed introduction later .
• src/main.rs It comes with the creation of the project Hello World file .

2. Specify the version management system

cargo Created by default for us git Warehouse , because git Is a commonly used management system , in addition to ,cargo You can also specify a version management system , Use --vcs Specify parameters or switch the version management system , If the folder already has a warehouse , Then the warehouse will not be created by default .

cargo new --vcs=git

--vcs The options are

optional
git, hg, pijul, fossil, none

3. Cargo.toml The configuration file

Cargo.toml The file USES TOML Configuration format , stay TOML In the format

• [section] Called a segment Title
• name = value Configuration items under the form configuration Title

The configuration file for the project , You can open... With a text editor , The contents are as follows

[package]
name = "hello_cargo"
version = "0.1.0"
edition = "2021"

[dependencies]

1. [package] It is used to manage the information of the current project package
   – name Indicates that the project name is hello_cargo
   – version Indicates that the project version number is 0.1.0
   – edition Indicates the Rust Version number
2. [dependencies] It is used to manage the dependency information of the current project package . stay Rust in , The code package is called crates. This project doesn't need anything else crate, However, dependency will be used in later projects , This clip will be used at that time .

Two 、 Build and run Cargo project

Use cargo Running the program is different from running the program manually , To run the program manually, you need to compile , And then it runs again , stay cargo We can complete this operation in one step ,cargo This process is automatically managed for us .

1. Build the project

Build the project using the following commands ,

cargo build

After operation , The compilation is successful, as shown in the figure below ,

here cargo Just compile the project for us , find hello_cargo\target\debug Directory, you can see our compiled executable , This is the same as the file we execute on the command line

The executable program runs the same as before

Cargo.lock file

If the project compiles normally , Will generate a Cargo.lock file , This file records the actual version the project depends on . Just you yourself? forever You don't need to touch this file , Give Way Cargo Just deal with it .

2. Run the project

Use cargo To run the project , Use the following command

cargo run

The operation effect is the same as that of our manual operation ,run The compilation and running steps will be automatically executed , We have compiled above , Therefore, the runtime does not need to compile again ,cargo Become very intelligent .

After being modified again, there will be a compilation process

3. Check code

Cargo It also provides a tool for code checking , This command quickly checks the code to ensure that it can be compiled , But it does not produce executable files ：

cargo check

When we do it , There is no wrong report , There is no problem with the code .

3、 ... and 、 Release Cargo project

When publishing a project , We use the following commands to optimize the compilation project , In order to let Rust Code runs faster , However, enabling these optimizations also takes longer compilation time .

cargo build --release 

1. Debug It's for development , You need to rebuild frequently and quickly ;
2. Release Is to build the final program for users , They don't often rebuild , And I hope the program can run as fast as possible .

Finally, you can target/release Find the final executable file under .

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summary

Let's review what we have learned Cargo Content ：

1. have access to cargo new Create project .
2. have access to cargo build Build the project .
3. have access to cargo run Build and run the project in one step .
4. have access to cargo check Build the project to check for errors without generating binaries .
5. It is different from putting the build results in the same directory as the source code ,Cargo Will put it in target/debug Catalog .