Command-line argument parsing: Difference between revisions

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{{short description|Programming languages parsing of command-line arguments}}

Different '''Commandcommand-line argument parsing''' methods are used by different [[programming languages]] to [[parse]] [[command-line argument]]s.

==Programming languages==

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An example of [[C (programming language)|C]] argument parsing would be:

<sourcesyntaxhighlight lang="Cc">

#include <stdio.h>

int main (int argc, char *argv[])

{

int count;

for (count = 0; count < argc; count++)

puts (argv[count]);

}

</syntaxhighlight>

</source>

C also has functions called [[getopt]] and getopt_long.

===C#===

An example of [[C Sharp (programming language)|C#]] argument parsing would be:

<syntaxhighlight lang="csharp">

class Program

{

static void Main(string[] args)

{

foreach (var arg in args)

Console.WriteLine(arg);

}

}

</syntaxhighlight>

===Java===

An example of [[Java (programming language)|Java]] argument parsing would be:

<sourcesyntaxhighlight lang="java">

public class Echo {

public static void main (String[] args) {

Line 27 ⟶ 42:

}

}

</syntaxhighlight>

</source>

===Kotlin===

Here are some possible ways to print arguments in [[Kotlin (programming language)|Kotlin]]:<ref>{{cite web|url=https://kotlinlang.org/docs/basic-syntax.html#program-entry-point |title=Kotlin: Basic syntax |date= |accessdate=2022-05-13}}</ref>

<syntaxhighlight lang="kotlin">

fun main(args: Array<String>) = println(args.joinToString())

</syntaxhighlight>

<syntaxhighlight lang="kotlin">

fun main(args: Array<String>) = println(args.contentToString())

</syntaxhighlight>

<syntaxhighlight lang="kotlin">

fun main(args: Array<String>) {

for (arg in args)

println(arg)

}

</syntaxhighlight>

===Perl===

[[Perl]] uses <code>$@ARGV</code>.

<sourcesyntaxhighlight lang="perl">

foreach $arg (@ARGV)

{

print $arg;

}

</syntaxhighlight>

</source>

or

<sourcesyntaxhighlight lang="perl">

foreach $argnum (0 .. $#ARGV)

{

print $ARGV[$argnum];

}

</syntaxhighlight>

</source>

===AWK===

[[AWK]] uses <code>ARGV</code> also.

<sourcesyntaxhighlight lang="awk">

BEGIN {

for ( i = 0; i < ARGC; i++ )

Line 56 ⟶ 89:

}

}

</syntaxhighlight>

</source>

===PHP===

[[PHP]] uses <code>argc</code> as a count of arguments and <code>argv</code> as an [[array data structure|array]] containing the values of the arguments.<ref>{{cite web|url=http://php.net/manual/en/reserved.variables.argv.php |title=PHP Manual |publisher=PHP |date= |accessdate=2010-05-31}}</ref><ref>[[wikibooks:PHP Programming/CLI]]</ref> To create an array from command-line arguments in the <code>-foo:bar</code> format, the following might be used:

<sourcesyntaxhighlight lang="php">

$args = parseArgs($argv);

echo getArg($args, '"foo'");

function parseArgs(array $args)

{

foreach ($args as $arg) {

$tmp = explode('":'", $arg, 2);

if ($arg[0] === '"-'") {

$args[substr($tmp[0], 1)] = $tmp[1];

}

Line 83 ⟶ 116:

return false;

}

</syntaxhighlight>

</source>

PHP can also use <code>getopt()</code>.<ref>{{Cite web|url=https://php.net/getopt|title = PHP: Getopt - Manual}}</ref>

===Python===

[[Python (programming language)|Python]] uses <code>sys.argv</code>, e.g.:

<sourcesyntaxhighlight lang="python">

import sys

for arg in sys.argv:

print arg

</syntaxhighlight>

</source>

Python also has a module called <code>argparse</code> in the standard library for parsing command-line arguments.<ref>{{cite web|title=argparse — Parser for command-line options, arguments and sub-commands|url=https://docs.python.org/3/library/argparse.html|url-status=live|work=Python v2v3.710.20 documentation|accessdate=715 MarchOctober 2021|archive-url=https://web.archive.org/web/20121101061815/http://docs.python.org:80/3/library/argparse.html |archive-date=2012-11-01 }}</ref>

===Racket===

[[Racket (programming language)|Racket]] uses a <code>current-command-line-arguments</code> parameter, and provides a <code>racket/cmdline</code><ref>[http://docs.racket-lang.org/reference/Command-Line_Parsing.html The Racket reference manual, Command-Line Parsing]</ref> library for parsing these arguments. Example:

<sourcesyntaxhighlight lang="racket">

#lang racket

Line 122 ⟶ 155:

(if (nose?) "-" "")

(if (smile?) ")" "("))

</syntaxhighlight>

</source>

The library parses long and short flags, handles arguments, allows combining short flags, and handles <code>-h</code> and <code>--help</code> automatically:

<sourcesyntaxhighlight lang="console">

$ racket /tmp/c -nfe 8

8-(

</syntaxhighlight>

</source>

===Node.jsRexx===

[[Rexx]] uses <code>arg</code>, e.g.:

<syntaxhighlight lang="rexx">

do i=1 to words(arg(1))

say word(arg(1), i)

end

</syntaxhighlight>

===Rust===

The args are in <code>env::args()</code>.<ref>{{cite web |title=Accepting Command Line Arguments - The Rust Programming Language |url=https://doc.rust-lang.org/book/ch12-01-accepting-command-line-arguments.html |website=doc.rust-lang.org |access-date=22 December 2022}}</ref>

<syntaxhighlight lang="rust">

use std::env;

fn main() {

let args: Vec<String> = env::args().collect();

let query = &args[1];

let file_path = &args[2];

println!("Searching for {}", query);

println!("In file {}", file_path);

}

</syntaxhighlight>

===JavaScript===

====Node.js====

[[JavaScript]] programs written for [[Node.js]] use the <code>process.argv</code> global variable.<ref>{{cite web|title=process.argv|work=Node.js v10.16.3 Documentation|url=https://nodejs.org/docs/latest-v10.x/api/process.html#process_process_argv|accessdate=3 October 2019}}</ref>

<sourcesyntaxhighlight lang="javascript">

// argv.js

console.log(process.argv);

</syntaxhighlight>

</source>

<sourcesyntaxhighlight lang="bash">

$ node argv.js one two three four five

[ 'node',

Line 146 ⟶ 204:

'four',

'five' ]

</syntaxhighlight>

</source>

[[Node.js]] programs are invoked by running the interpreter node interpreter with a given file, so the first two arguments will be <code>node</code> and the name of the JavaScript source file. It is often useful to extract the rest of the arguments by slicing a sub-array from <code>process.argv</code>.<ref>{{cite web|title=How to parse command line arguments|work=Node.js Foundation Documentation|accessdate=3 October 2019|url=https://nodejs.org/en/knowledge/command-line/how-to-parse-command-line-arguments/}}</ref>

<sourcesyntaxhighlight lang="javascript">

// process-args.js

console.log(process.argv.slice(2));

</syntaxhighlight>

</source>

<sourcesyntaxhighlight lang="bash">

$ node process-args.js one two=three four

[

Line 161 ⟶ 219:

'two=three',

'four' ]

</syntaxhighlight>

</source>

====Bun====

JavaScript written for [[Bun (software)|Bun]] use <code>Bun.argv</code> and the <code>util.parseArgs</code> function.<ref>{{cite web |title=Parse command-line arguments {{!}} Bun Examples |url=https://bun.sh/guides/process/argv |website=Bun |language=en}}</ref>

<syntaxhighlight lang="javascript">

console.log(Bun.argv);

</syntaxhighlight>

====Deno====

JavaScript written for [[Deno (software)|Deno]] use <code>Deno.args</code><ref>{{cite web |title=Deno.args |url=https://docs.deno.com/api/deno/~/Deno.args |website=docs.deno.com}}</ref> and the <code>parseArgs</code> function.<ref>{{cite web |title=parseArgs from parse-args - @std/cli - JSR |url=https://jsr.io/@std/cli/doc/parse-args/~/parseArgs |website=jsr.io |language=en}}</ref>

<syntaxhighlight lang="javascript">

console.log(Deno.args);

</syntaxhighlight>

==References==

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[[Category:Articles with example Java code]]

[[Category:Articles with example PHP code]]

[[Category:Articles with example Python (programming language) code]]

[[Category:Articles with example Racket code]]