blocks|key|350366|text|barjak+said适用于字符串，但如果需要将参数转换为数字(在本例中为uint)，则需要进行如下转换：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|350367|fn+main()+{
++++let+arg+:+~[~str]+=+os::args();
++++match+uint::from_str(arg[1]){
+++++++++Some(x)=>io::println(fmt!("%25u",someFunction(x))),
+++++++++None=>io::println("I+need+a+real+number")
++++}
}|code-block|syntax|javascript|350368|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/15619320/how-can-i-access-command-line-parameters/15621897#15621897^0|0|B|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

What <a href="https://stackoverflow.com/questions/15619320/how-can-i-access-command-line-parameters/15621897#15621897">barjak said</a> works for strings, but if you need the argument as a number (in this case a uint) you need to convert like this:
<pre><code>fn main() {
 let arg : ~[~str] = os::args();
 match uint::from_str(arg[1]){
 Some(x)=&gt;io::println(fmt!(&quot;%u&quot;,someFunction(x))),
 None=&gt;io::println(&quot;I need a real number&quot;)
 }
}
</code></pre>

blocks|key|350392|text|Rust在getopts+crate中具有getopt-style命令行界面参数解析功能。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|350393|entityMap|0|LINK|mutability|MUTABLE|url|https://crates.io/crates/getopts^0|L|6|5|D|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

Rust has <code>getopt</code>-style CLI argument parsing in the <a href="https://crates.io/crates/getopts" rel="nofollow noreferrer">getopts crate</a>.

blocks|key|132471|text|从0.8/0.9版本开始，函数args()的正确路径为::std::os::args，即：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|132472|fn+main()+{
++let+args:+~[~str]+=+::std::os::args();
++println(args[0]);
}|code-block|syntax|javascript|132473|看起来Rust现在仍然是非常不稳定的，即使是标准的I/O，所以这可能很快就会过时。|132474|entityMap^0|R|F|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

As of version 0.8/0.9, the correct path to the function args() would be <code>::std::os::args</code>, i.e.:
<pre><code>fn main() {
 let args: ~[~str] = ::std::os::args();
 println(args[0]);
}
</code></pre>
It seems that Rust is still pretty volatile right now with even standard I/O, so this may become out of date fairly quickly.

blocks|key|132486|text|Rust自2013年5月的Calvin's+answer以来一直在进化。现在可以使用as_slice()解析命令行参数|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|132487|use+std::os;

fn+seen_arg(x:+uint)
{+++++++
++++println!("you+passed+me+{}",+x);
}
fn+main()+{
++++let+args+=+os::args();
++++let+args+=+args.as_slice();
++++let+nitems+=+{
++++++++++++if+args.len()+==+2+{
++++++++++++++++++++from_str::<uint>(args[1].as_slice()).unwrap()
++++++++++++}+else+{
++++++++++++++++++++10000
++++++++++++}
++++};

++++seen_arg(nitems);
}|code-block|syntax|javascript|132488|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/15619320/how-can-i-access-command-line-parameters/16500034#16500034^0|16|A|D|F|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Rust has evolved since <a href="https://stackoverflow.com/questions/15619320/how-can-i-access-command-line-parameters/16500034#16500034">Calvin's answer</a> from May 2013. Now one would parse command line arguments with <code>as_slice()</code>:
<pre><code>use std::os;

fn seen_arg(x: uint)
{ 
 println!(&quot;you passed me {}&quot;, x);
}
fn main() {
 let args = os::args();
 let args = args.as_slice();
 let nitems = {
 if args.len() == 2 {
 from_str::&lt;uint&gt;(args[1].as_slice()).unwrap()
 } else {
 10000
 }
 };

 seen_arg(nitems);
}
</code></pre>

blocks|key|132517|text|Docopt也可用于Rust，它从用法字符串为您生成解析器。在Rust中的一个额外好处是，宏可以用于自动生成结构并进行基于类型的解码：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|132518|docopt!(Args,+"
Usage:+cp+[-a]+SOURCE+DEST
+++++++cp+[-a]+SOURCE...+DIR

Options:
++++-a,+--archive++Copy+everything.
")|code-block|syntax|javascript|132519|您可以使用以下命令获取参数：|132520|let+args:+Args+=+Args::docopt().decode().unwrap_or_else(%7Ce%7C+e.exit());|132521|自述文件和documentation有大量完整的工作示例。|132522|免责声明:我是这个库的作者之一。|132523|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/docopt/docopt.rs|1|https://docs.rs/docopt^0|0|6|0|0|0|0|0|5|D|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|O|3|P|5|6|7|1B|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

<a href="https://github.com/docopt/docopt.rs" rel="nofollow noreferrer">Docopt</a> is also available for Rust, which generates a parser for you from a usage string. As a bonus in Rust, a macro can be used to automatically generate the struct and do type based decoding:
<pre><code>docopt!(Args, &quot;
Usage: cp [-a] SOURCE DEST
 cp [-a] SOURCE... DIR

Options:
 -a, --archive Copy everything.
&quot;)
</code></pre>
And you can get the arguments with:
<pre><code>let args: Args = Args::docopt().decode().unwrap_or_else(|e| e.exit());
</code></pre>
The README and <a href="https://docs.rs/docopt" rel="nofollow noreferrer">documentation</a> have plenty of full working examples.
Disclaimer: I am one of the authors of this library.

blocks|key|132566|text|对我来说，getopts总是感觉太低级，而docopt.rs太神奇了。我想要一些明确和直接的东西，仍然提供所有的功能，如果我需要他们。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|132567|这就是clap-rs派上用场的地方。|offset|length|132568|感觉有点像Python中的argparse。下面是一个示例，展示了它的外观：|132569|let+matches+=+App::new("myapp")
++++++++++++++++++++++.version("1.0")
++++++++++++++++++++++.author("Kevin+K.+<kbknapp@gmail.com>")
++++++++++++++++++++++.about("Does+awesome+things")
++++++++++++++++++++++.arg(Arg::with_name("CONFIG")
+++++++++++++++++++++++++++.short("c")
+++++++++++++++++++++++++++.long("config")
+++++++++++++++++++++++++++.help("Sets+a+custom+config+file")
+++++++++++++++++++++++++++.takes_value(true))
++++++++++++++++++++++.arg(Arg::with_name("INPUT")
+++++++++++++++++++++++++++.help("Sets+the+input+file+to+use")
+++++++++++++++++++++++++++.required(true)
+++++++++++++++++++++++++++.index(1))
++++++++++++++++++++++.arg(Arg::with_name("debug")
+++++++++++++++++++++++++++.short("d")
+++++++++++++++++++++++++++.multiple(true)
+++++++++++++++++++++++++++.help("Sets+the+level+of+debugging+information"))
++++++++++++++++++++++.get_matches();|code-block|syntax|javascript|132570|你可以像这样访问你的参数：|132571|println!("Using+input+file:+{}",+matches.value_of("INPUT").unwrap());

//+Gets+a+value+for+config+if+supplied+by+user,+or+defaults+to+"default.conf"
let+config+=+matches.value_of("CONFIG").unwrap_or("default.conf");
println!("Value+for+config:+{}",+config);|132572|(从official+documentation复制)|132573|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/kbknapp/clap-rs|1|https://github.com/kbknapp/clap-rs#quick-example^0|0|3|7|0|0|0|0|0|0|2|M|1|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@$D|14|E|15|1|16]]|A|$]]|$1|F|3|G|5|6|7|17|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|18|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|1A|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@$D|1C|E|1D|1|1E]]|A|$]]|$1|S|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]|10|$5|V|W|X|A|$Y|11]]]]

For me, getopts always felt too low-level and docopt.rs was too much magic.
I want something explicit and straightforward that still provides all the features if I need them.

This is where <a href="https://github.com/kbknapp/clap-rs" rel="noreferrer">clap-rs</a> comes in handy. 
It feels a bit like argparse from Python.
Here is an example of how it looks like:

<pre><code>let matches = App::new("myapp")
 .version("1.0")
 .author("Kevin K. &lt;kbknapp@gmail.com&gt;")
 .about("Does awesome things")
 .arg(Arg::with_name("CONFIG")
 .short("c")
 .long("config")
 .help("Sets a custom config file")
 .takes_value(true))
 .arg(Arg::with_name("INPUT")
 .help("Sets the input file to use")
 .required(true)
 .index(1))
 .arg(Arg::with_name("debug")
 .short("d")
 .multiple(true)
 .help("Sets the level of debugging information"))
 .get_matches();
</code></pre>

You can access your parameters like so:

<pre><code>println!("Using input file: {}", matches.value_of("INPUT").unwrap());

// Gets a value for config if supplied by user, or defaults to "default.conf"
let config = matches.value_of("CONFIG").unwrap_or("default.conf");
println!("Value for config: {}", config);
</code></pre>

(Copied from the <a href="https://github.com/kbknapp/clap-rs#quick-example" rel="noreferrer">official documentation</a>)

blocks|key|350530|text|也可以查看structopt：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|350531|extern+crate+structopt;
#[macro_use]
extern+crate+structopt_derive;

use+structopt::StructOpt;

#[derive(StructOpt,+Debug)]
#[structopt(name+=+"example",+about+=+"An+example+of+StructOpt+usage.")]
struct+Opt+{
++++///+A+flag,+true+if+used+in+the+command+line.
++++#[structopt(short+=+"d",+long+=+"debug",+help+=+"Activate+debug+mode")]
++++debug:+bool,

++++///+An+argument+of+type+float,+with+a+default+value.
++++#[structopt(short+=+"s",+long+=+"speed",+help+=+"Set+speed",+default_value+=+"42")]
++++speed:+f64,

++++///+Needed+parameter,+the+first+on+the+command+line.
++++#[structopt(help+=+"Input+file")]
++++input:+String,

++++///+An+optional+parameter,+will+be+`None`+if+not+present+on+the
++++///+command+line.
++++#[structopt(help+=+"Output+file,+stdout+if+not+present")]
++++output:+Option<String>,
}

fn+main()+{
++++let+opt+=+Opt::from_args();
++++println!("{:?}",+opt);
}|code-block|syntax|javascript|350532|https://github.com/TeXitoi/structopt|offset|length|350533|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|10|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

Also check out structopt:

<pre><code>extern crate structopt;
#[macro_use]
extern crate structopt_derive;

use structopt::StructOpt;

#[derive(StructOpt, Debug)]
#[structopt(name = "example", about = "An example of StructOpt usage.")]
struct Opt {
 /// A flag, true if used in the command line.
 #[structopt(short = "d", long = "debug", help = "Activate debug mode")]
 debug: bool,

 /// An argument of type float, with a default value.
 #[structopt(short = "s", long = "speed", help = "Set speed", default_value = "42")]
 speed: f64,

 /// Needed parameter, the first on the command line.
 #[structopt(help = "Input file")]
 input: String,

 /// An optional parameter, will be `None` if not present on the
 /// command line.
 #[structopt(help = "Output file, stdout if not present")]
 output: Option&lt;String&gt;,
}

fn main() {
 let opt = Opt::from_args();
 println!("{:?}", opt);
}
</code></pre>

<a href="https://github.com/TeXitoi/structopt" rel="nofollow noreferrer">https://github.com/TeXitoi/structopt</a>

blocks|key|350556|text|如果您想遍历命令行参数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|350557|use+std::env::{args,Args};

fn+main()+{
++++let+mut+args:Args=args();
++++//+args.nth(0)+cannot+borrow+as+mutable.+that+is+why++let+mut+args
++++//+nth+return+an+element+of+iterator
++++let+first=args.nth(1).unwrap();
++++//+iterator+has+next+method.+we+want+to+get+the+first+element+of+next+iterator.+NOT+args.nth(2)
++++//+chars+returns+an+iterator
++++let+operator=args.nth(0).unwrap().chars().next().unwrap();
++++let+second=args.nth(0).unwrap();
}|code-block|syntax|javascript|350558|如果您想要直接访问第n个参数：|350559|fn+get_nth_arg(n:usize)->String{
++++std::env::args().nth(n).unwrap()
}|350560|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you want to iterate over command-line arguments:
<pre><code>use std::env::{args,Args};

fn main() {
 let mut args:Args=args();
 // args.nth(0) cannot borrow as mutable. that is why let mut args
 // nth return an element of iterator
 let first=args.nth(1).unwrap();
 // iterator has next method. we want to get the first element of next iterator. NOT args.nth(2)
 // chars returns an iterator
 let operator=args.nth(0).unwrap().chars().next().unwrap();
 let second=args.nth(0).unwrap();
}
</code></pre>
If you want to access the n'th argument directly:
<pre><code>fn get_nth_arg(n:usize)-&gt;String{
 std::env::args().nth(n).unwrap()
}
</code></pre>

The <a href="https://doc.rust-lang.org/book/guessing-game.html" rel="nofollow noreferrer">Rust tutorial</a> does not explain how to take parameters from the command line. <code>fn main()</code> is only shown with an empty parameter list in all examples.
What is the correct way of accessing command line parameters from <code>main</code>?

How can I access command line parameters?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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没有解释如何从命令行获取参数。在所有示例中，fn main()都只显示空的参数列表。从main访问命令行参数的正确方法是什么

问如何访问命令行参数？
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