Every language
10 lenguajes, copy-ready. One at a time with syntax highlighting, or all inline.
JSJavaScript
// greet.js — node greet.js --name Ada
const args = process.argv.slice(2);
const i = args.indexOf('--name');
const name = i !== -1 ? args[i + 1] : 'world';
console.log(`Hello, ${name}!`);argv[0] is the node binary and argv[1] the script — slice(2) is the user's part.
TSTypeScript
const args: string[] = process.argv.slice(2);
const name = args.find((_, i) => args[i - 1] === '--name') ?? 'world';
console.log(`Hello, ${name}!`);Same slice(2) offset as Node. For real flag parsing use util.parseArgs (built in since Node 18.3).
GoGo
package main
import "flag"
func main() {
name := flag.String("name", "world", "who to greet")
flag.Parse()
println("Hello, " + *name + "!")
}The stdlib flag package handles --name Ada and --name=Ada. Positional args follow flag.Args().
RsRust
fn main() {
let name = std::env::args()
.skip(1)
.find(|a| !a.starts_with('-'))
.unwrap_or_else(|| "world".into());
println!("Hello, {name}!");
}args() panics on non-UTF8; args_os() keeps raw OsStrings. clap is the crate for real CLIs.
PHPPHP
<?php
// greet.php — php greet.php Ada
$name = $argv[1] ?? 'world';
echo "Hello, $name!", PHP_EOL;$argv[0] is the script name. Use getopt() for flags: getopt('', ['name:'])['name'].
PyPython
import argparse
parser = argparse.ArgumentParser(description='Greet someone.')
parser.add_argument('--name', default='world', help='who to greet')
args = parser.parse_args()
print(f'Hello, {args.name}!')argparse builds --help for free and exits non-zero on bad input.
CC
#include <stdio.h>
int main(int argc, char *argv[]) {
const char *name = argc > 1 ? argv[1] : "world";
printf("Hello, %s!\n", name);
return 0;
}argv[0] is the program path and argv[argc] is NULL — always guard before indexing.
C#C#
var name = args.Length > 0 ? args[0] : "world";
Console.WriteLine($"Hello, {name}!");Top-level statements (C# 9+): args arrives in Main for free. System.CommandLine is the flag parser.
SwSwift
let args = Array(CommandLine.arguments.dropFirst())
let name = args.first ?? "world"
print("Hello, \(name)!")arguments[0] is the executable path. SwiftArgumentParser is Apple's flag-parser package.
RbRuby
name = ARGV[0] || 'world'
puts "Hello, #{name}!"ARGV holds only the arguments. For flags use the built-in optparse: require 'optparse'.