rust标准库std::env环境相关的常量

ARCH	
DLL_EXTENSION
DLL_PREFIX	
DLL_SUFFIX	
EXE_EXTENSION
EXE_SUFFIX	
FAMILY
OS

    use std::env;
    println!("ARCH = {}", env::consts::ARCH);
    println!("DLL_EXTENSION = {}", env::consts::DLL_EXTENSION);
    println!("DLL_PREFIX = {}", env::consts::DLL_PREFIX);
    println!("DLL_SUFFIX = {}", env::consts::DLL_SUFFIX);
    println!("EXE_EXTENSION = {}", env::consts::EXE_EXTENSION);
    println!("EXE_SUFFIX = {}", env::consts::EXE_SUFFIX);
    println!("FAMILY = {}", env::consts::FAMILY);
    println!("OS = {}", env::consts::OS);
// 显示结果：
ARCH = x86_64
DLL_EXTENSION = so
DLL_PREFIX = lib
DLL_SUFFIX = .so
EXE_EXTENSION = 
EXE_SUFFIX = 
FAMILY = unix
OS = linux

args	返回命令行传递的参数
args_os	返回当前进程的参数
current_dir	返回当前的工作目录，该目录保存在PathBuf中
current_exe	返回当前可执行程序的全路径
home_dir	返回当前用户目录的路径
join_paths	添加一些环境变量到PATH这个变量中
remove_var	删除当前运行进程的环境变量（系统中的环境变量不会改变，只改变当前进程的环境变量）
set_current_dir	指定当前可执行程序的工作目录
set_var	将当前进程的环境变量修改为新的值
split_paths	Parses input according to platform conventions for the PATH environment variable.
temp_dir	返回临时文件所存放的目录
var	从当前进程获取环境变量，通过环境变量的key值获取value值
var_os	Fetches the environment variable key from the current process, returning None if the variable isn't set.
vars	Returns an iterator of (variable, value) pairs of strings, for all the environment variables of the current process.
vars_os	Returns an iterator of (variable, value) pairs of OS strings, for all the environment variables of the current process.

use std::env;
​
fn main() {
    let args: Vec<String> = env::args().collect();
    dbg!(args);
}

cargo run -- search filename.txt

use std::env;
​
fn main() {
    let args: Vec<String> = env::args().collect();
    let param_name = &args[1];
    let file_name = &args[2];
    println!("第一个参数名:{}", param_name);
    println!("第二个参数名:{}", file_name);
}

use std::env;
​
fn main() {
    for (key, value) in env::vars() {
        println!("{} => {}", key, value);
    }
}

use std::env;
​
fn main() {
    let search_key = "PATH";
    match env::var(search_key) {
        Ok(val) => {
            println!("PATH变量保存的内容为:{}", val);
        },
        Err(e) => println!("无法找到key:{}, 错误为:{}", search_key, e)
    }
}