Command-line argument parsing

Different Command-line argument parsing methods are used by different programming languages to parse command-line arguments.

Programming languages

C

Main article: C_syntax#Command-line_arguments

C uses argv to process command-line arguments.^[1]

Java

An example of Java argument parsing would be:

public class Echo {
    public static void main (String[] args) {
        for (String s: args) {
            System.out.println(s);
        }
    }
}

Perl

Perl uses $ARGV.

PHP

PHP uses argc as a count of arguments and argv as an array containing the values of the arguments.^[2][3] To create an array from command-line arguments in the -foo:bar format, the following might be used:

$args = parseArgs( $argv );
echo getArg( $args, 'foo' );
 
function parseArgs( $args ) {
        foreach( $args as $arg ) {
                $tmp = explode( ':', $arg, 2 );
                if( $arg[0] == "-" ) {
                        $args[ substr( $tmp[0], 1 ) ] = $tmp[1];
                }
        }
        return $args;
}
 
function getArg( $args, $arg ) {
        if( isset( $args[$arg] ) ) {
                return $args[$arg];
        }
        return false;
}

PHP can also use getopt()^[4]

Python

Python uses sys.argv, e.g.:

import sys
for arg in sys.argv:
  print arg

Racket

Racket uses a current-command-line-arguments parameter, and provides a racket/cmdline^[5] library for parsing these arguments. Example:

#lang racket
(require racket/cmdline)
(define smile? #true)
(define nose?  #false)
(define eyes   ":")
(command-line
 #:program "emoticon"
 #:once-any ; the following two are mutually exclusive
 [("-s" "--smile") "smile mode" (set! smile? #true)]
 [("-f" "--frown") "frown mode" (set! smile? #false)]
 #:once-each
 [("-n" "--nose") "add a nose"  (set! nose? #true)]
 [("-e" "--eyes") char "use <char> for the eyes" (set! eyes char)])
(printf "~a~a~a\n" eyes (if nose? "-" "") (if smile? ")" "("))

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

$ racket /tmp/c -nfe 8
8-(

References

1. ^ "The C Book — Arguments to main". Publications.gbdirect.co.uk. http://publications.gbdirect.co.uk/c_book/chapter10/arguments_to_main.html. Retrieved 2010-05-31. 
2. ^ "PHP Manual". PHP. http://php.net/manual/en/reserved.variables.argv.php. Retrieved 2010-05-31. 
3. ^ wikibooks:PHP Programming/CLI
4. ^ http://php.net/getopt
5. ^ The Racket reference manual, Command-Line Parsing