Command-line arguments

Command-line arguments
You are encouraged to solve this task according to the task description, using any language you may know.

Retrieve the list of command-line arguments given to the program.

Example command line:

myprogram -c "alpha beta" -h "gamma"

Ada

Command line arguments are available through the pre-defined package Ada.Command_Line.

with Ada.Command_line; use Ada.Command_Line;
with Ada.Text_IO; use Ada.Text_IO

procedure Print_Commands is
begin
   -- The number of command line arguments is retrieved from the function Argument_Count
   -- The actual arguments are retrieved from the function Argument
   -- The program name is retrieved from the function Command_Name
   Put(Command_Name & " ");
   for Arg in 1..Argument_Count loop
      Put(Argument(Arg) & " ");
   end loop;
   New_Line;
end Print_Commands;

C

Command line arguments are passed to main. Since the program name is also passed as "argument", the provided count is actually one more than the number of program arguments. Traditionally the argument count is named argc and the array of argument strings is called argv, but that's not mandatory; any (non-reserved) name will work just as well. It is, however, a good idea to stick to the conventional names.

Be careful on systems that use Unicode or other multibyte character sets. You may need to use a type of _wchar* and multi-byte-character-set-aware versions of printf.

 #include <stdio.h>
 
 int main(int argc, char* argv[])
 {
   int i;
   printf("This program is named %s.\n", argv[0]);
   for (i = 1; i < argc; ++i)
     printf("the argument #%d is %s\n", i, argv[i]);
 }

C++

Command line arguments are passed the same was as in C.

This example uses iostream. Traditional C I/O also works.

#include <iostream>

int main(int argc, char* argv[])
{
  std::cout << "This program is named " << argv[0] << "\n";
  std::cout << "There are " << argc-1 << " arguments given.\n";
  for (int i = 1; i < argc; ++i)
    std::cout << "the argument #" << i << " is " << argv[i] << "\n";
}

Clean

getCommandLine from the module ArgEnv returns an array of command-line arguments (the first element is the name of the program).

import ArgEnv

Start = getCommandLine

E

interp.getArgs()

Java

public class arguments {
  public static void main(String[] args) {
     System.out.println("There are " + args.length + " arguments given.");
     for(int i = 0;i<args.length;i++) 
        System.out.println("The argument #" + (i+1) + " is " + args[i]);
  }
}

Perl

Interpreter: Perl v5.x

@ARGV is the array containing all command line parameters

my @params = @ARGV;
my $second = $ARGV[1];
my $fifth = $ARGV[4];

Python

argv in the sys module is a list containing all command line parameters, including the program name.

import sys
program_name = sys.argv[0] # gets the program name
all_arguments = sys.argv[1:] # arguments, excluding the program name

Tcl

The pre-defined variable argc contains the number of arguments passed to the routine, argv contains the arguments as a list. Retrieving the second argument might look something like this:

 if { $argc > 1 } { puts [lindex $argv 1] }

(Tcl counts from zero, thus [lindex $list 1] retrieves the second item in the list)

UNIX Shell

Bourne Shell

To retrieve the entire list of arguments:

WHOLELIST="$@"

To retrieve the second and fifth arguments:

SECOND=$2
FIFTH=$5