Command-line argument parsing
Different Command-line argument parsing methods are used by different programming languages to parse command-line arguments.
Programming languages
C
C uses argv to process command-line arguments.[1][2]
An example of C argument parsing would be:
#include <stdio.h>
int main (int argc, char *argv[])
{
int count;
for (count=0; count<argc; count++)
puts (argv[count]);
}
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);
}
}
}
Bash
Bash uses $1 $2 ... ($0 is the script filename).
echo $1
echo $2
...
or
for p in "$@"
do
echo $p
done
Perl
Perl uses $ARGV.
foreach $arg (@ARGV)
{
print $arg;
}
or
foreach $argnum (0 .. $#ARGV)
{
print $ARGV[$argnum];
}
AWK
AWK uses ARGV also.
BEGIN {
for ( i = 0; i < ARGC; i++ )
{
print ARGV[i]
}
}
PHP
PHP uses argc as a count of arguments and argv as an array containing the values of the arguments.[3][4] 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().[5]
Python
Python uses sys.argv, e.g.:
import sys
for arg in sys.argv:
print arg
Python also has a module called argparse in the standard library for parsing command-line arguments.[6]
Racket
Racket uses a current-command-line-arguments parameter, and provides a racket/cmdline[7] library for parsing these arguments. Example:
#lang racket
(require racket/cmdline)
(define smile? (make-parameter #t))
(define nose? (make-parameter #false))
(define eyes (make-parameter ":"))
(command-line #:program "emoticon"
#:once-any ; the following two are mutually exclusive
[("-s" "--smile") "smile mode" (smile? #true)]
[("-f" "--frown") "frown mode" (smile? #false)]
#:once-each
[("-n" "--nose") "add a nose" (nose? #true)]
[("-e" "--eyes") char "use <char> for the eyes" (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
- ↑ "The C Book — Arguments to main". Publications.gbdirect.co.uk. Retrieved 2010-05-31.
- ↑ An example of parsing C arguments and options
- ↑ "PHP Manual". PHP. Retrieved 2010-05-31.
- ↑ wikibooks:PHP Programming/CLI
- ↑ https://php.net/getopt
- ↑ "argparse — Parser for command-line options, arguments and sub-commands". Python v2.7.2 documentation. Retrieved 7 March 2012.
- ↑ The Racket reference manual, Command-Line Parsing