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 predefined package Ada.Command_Line.
<lang ada>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;</lang>
BASIC
<lang freebasic>DIM i AS Integer
PRINT "This program is named "; Command$(0) i = 1 DO WHILE(LEN(Command$(i)))
PRINT "The argument "; i; " is "; Command$(i) i = i+1
LOOP</lang>
See also: RapidQ
C
Command line arguments are passed to main. Since the program name is also passed as "argument", the provided count is actually one more than the number of program arguments. Traditionally the argument count is named argc and the array of argument strings is called argv, but that's not mandatory; any (non-reserved) name will work just as well. It is, however, a good idea to stick to the conventional names.
Be careful on systems that use Unicode or other multibyte character sets. You may need to use a type of _wchar* and multi-byte-character-set-aware versions of printf.
<lang c>#include <stdio.h>
int main(int argc, char* argv[]) {
int i;
printf("This program is named %s.\n", argv[0]);
for (i = 1; i < argc; ++i)
printf("the argument #%d is %s\n", i, argv[i]);
}</lang>
C++
Command line arguments are passed the same way as in C.
This example uses iostream. Traditional C I/O also works.
<lang cpp>#include <iostream>
int main(int argc, char* argv[]) {
std::cout << "This program is named " << argv[0] << std::endl; std::cout << "There are " << argc-1 << " arguments given." << std::endl; for (int i = 1; i < argc; ++i) std::cout << "the argument #" << i << " is " << argv[i] << std::endl;
}</lang>
Clean
getCommandLine from the module ArgEnv returns an array of command-line arguments (the first element is the name of the program).
import ArgEnv Start = getCommandLine
D
<lang d>import std.stdio ;
void main(string[] args) {
foreach(i, e ; args[1..$])
writefln("#%2d : %s", i + 1, e) ;
}</lang>
DOS Batch File
@if not [%1]==[] echo %~1 & call %0 %2 %3 %4 %5 %6 %7 %8 %9
E
interp.getArgs()
Erlang
3> init:get_arguments().
result
[{root,["/usr/erlang/erl5.5"]},
{progname,["erl"]},
{home,["/home/me"]},
{c,["alpha beta"]},
{h,["gamma"]}]
init:get_argument(name) can be used to fetch value of a particular flag
4> init:get_argument(h).
{ok,"gamma"}
5> init:get_argument(c).
{ok,"alpha beta"}
Forth
Access to command line arguments is not a standard feature of Forth, since it is designed to be used without an operating system. The popular GNU implementation gforth runs from a shell and can access command line arguments similar to C: variable argc contains the count (including the command itself) and arg is a function that returns the nth argument as a string.
\ args.f: print each command line argument on a separate line : main argc @ 0 do i arg type cr loop ; main bye
Here is output from a sample run.
$ gforth args.f alpha "beta gamma" delta gforth args.f alpha beta gamma delta $
Haskell
Defined by the System module, getArgs :: IO [String] provides the command-line arguments in a list.
myprog.hs:
import System main = getArgs >>= print
myprog a -h b c => ["a","-h","b","c"]
J
The global ARGV holds the command line arguments.
Java
<lang 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] + "and is at index " + i);
}
}</lang>
LSE64
argc , nl # number of arguments (including command itself) 0 # argument dup arg dup 0 = || ,t 1 + repeat drop
Modula-3
Command line parameters are accessed using the Params module.
MODULE Args EXPORTS Main;
IMPORT IO, Params;
BEGIN
IO.Put(Params.Get(0) & "\n");
IF Params.Count > 1 THEN
FOR i := 1 TO Params.Count - 1 DO
IO.Put(Params.Get(i) & "\n");
END;
END;
END Args.
Output:
martin@thinkpad:~$ ./prog ./prog martin@thinkpad:~$ ./prog 10 ./prog 10 martin@thinkpad:~$ ./prog 10 20 ./prog 10 20
OCaml
The program name is also passed as "argument", so the array length is actually one more than the number of program arguments.
<lang ocaml>let () =
Printf.printf "This program is named %s.\n" Sys.argv.(0); for i = 1 to Array.length Sys.argv - 1 do Printf.printf "the argument #%d is %s\n" i Sys.argv.(i) done</lang>
Using the Arg module
<lang ocaml>(* default values *) let somebool = ref false let somestr = ref "" let someint = ref 0
let usage = "usage: " ^ Sys.argv.(0) ^ " [-b] [-s string] [-d int]"
let speclist = [
("-b", Arg.Unit (fun () -> somebool := true), ": set somebool to true");
("-s", Arg.String (fun s -> somestr := s), ": what follows -s sets some string");
("-d", Arg.Int (fun d -> someint := d), ": some int parameter");
]
let () =
(* Read the arguments *)
Arg.parse
speclist
(fun x -> raise (Arg.Bad ("Bad argument : " ^ x)))
usage;
Printf.printf " %b %d '%s'\n" !somebool !someint !somestr;
- </lang>
% ocaml arg.ml --help usage: tmp.ml [-b] [-s string] [-d int] -b : set somebool to true -s : what follows -s sets some string -d : some int parameter --help Display this list of options % ocaml arg.ml -d 4 -b -s blabla true 4 'blabla' % ocaml arg.ml false 0 ''
Perl
@ARGV is the array containing all command line parameters
<lang perl>my @params = @ARGV; my $second = $ARGV[1]; my $fifth = $ARGV[4];</lang>
PHP
When PHP is run from the command line, the special variables $argv and $argc contain the array of arguments, and the number of arguments, respectively. The program name is passed as the first argument.
<lang php><?php $program_name = $argv[0]; $second_arg = $argv[2]; ?></lang>
Pop11
variable poparglist contains list of command line arguments (as strings). One can use iteration over list to process then (for example print).
lvars arg; for arg in poparglist do printf(arg, '->%s<-\n'); endfor;
Python
sys.argv is a list containing all command line arguments, including the program name. Typically you slice the list to access the actual command line argument:
<lang python>import sys program_name = sys.argv[0] arguments = sys.argv[1:] count = len(arguments)</lang>
When running a module by invoking Python, the Python interpreter processes and removes some of the arguments, and the module cannot access them. To process command line arguments, run the module directly. sys.argv is a copy of the command line arguments; modifying sys.argv will not change the arguments seen by other processes, e.g. ps. (In other words sys.argv is an object which contains a copy of the process' command line arguments ... modifying that copy is only visible from within the Python program and not externally).
RapidQ
PRINT "This program is named "; Command$(0)
FOR i=1 TO CommandCount
PRINT "The argument "; i; " is "; Command$(i)
NEXT i
Raven
ARGS print
stack (6 items) 0 => "raven" 1 => "myprogram" 2 => "-c" 3 => "alpha beta" 4 => "-h" 5 => "gamma"
Ruby
Command line arguments are available in the constant Object::ARGV.
myprog: <lang ruby>#! /usr/bin/env ruby p ARGV</lang>
myprog a -h b c => ["a","-h","b","c"]
Tcl
The predefined 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 $list 1] retrieves the second item in the list)
Toka
Arguments are stored into an array. The first element in the array is the name of the program, the rest are the arguments in order. The number of arguments is provided by #args.
[ arglist array.get type cr ] is show-arg [ dup . char: = emit space ] is #= 1 #args [ i #= show-arg ] countedLoop
UNIX Shell
Bourne Shell
To retrieve the entire list of arguments:
WHOLELIST="$@"
To retrieve the second and fifth arguments:
SECOND=$2 FIFTH=$5
V
The arguments to the program are stored in the stack,
args.v
$stack puts
./args.v a b c =[args.v a b c]
Visual Basic .NET
This syntax will tokenize the command line arguments. Tokens are normally delimited by spaces, but spaces can be part of a token if surrounded by quotes.
Sub Main(ByVal args As String())
For Each token In args
Console.WriteLine(token)
Next
End Sub