• Go

var b = flag.Bool("b", false, "Do bat")
var f = flag.Bool("f", false, "Do fox")

func main() {
	flag.Parse()
	if *b {
		bar()
	}
	if *f {
		fox()
	}
}

• C

int main(int argc, char * argv[])
{
        int optch;
        while ((optch = getopt(argc, argv, "bf")) != -1) {
                switch (optch) {
                        case 'b': bat(); break;
                        case 'f': fox(); break;
                }
        }
        return 0;
}

• Clojure

(defn -main [arg & _]
  (case arg
    "b" (bat)
    "f" (fox)
    (nothing)))

• C#

void Main(string[] args)
{
  if (args.Contains("b")) bat();
  else if (args.Contains("f")) fox();
}

• D

void main(string[] args)
{
    void bat(){} void fox(){}
    getopt(args, "b", &bat, "f", &fox);
}

• Dart

if (args.contains("b")) bat();
if (args.contains("f")) fox();

• Fortran

  do i=1, command_argument_count ()
     call get_command_argument (i, length=length)
     if (length > len(opt)) then
        deallocate (opt)
        allocate (character(length) :: opt)
     end if
     call get_command_argument (i, opt)
     if (opt(1:1) /= '-') exit
     do j=2, length
        select case (opt(j:j))
        case ('b')
           print *,"bat"
        case ('f')
           print *,"fox"
        end select
     end do
  end do

• Haskell

do
  args <- getArgs
  when ("b" `elem` args) bat
  when ("f" `elem` args) fox

• JS

const args = process.argv.slice(2)
if (args.includes('b')) bat()
else if (args.includes('f')) fox()

• Java

var argsSet = Set.of(args);
if (argsSet.contains("b")) bat();
if (argsSet.contains("f")) fox();

• Java

public static void main(String[] args) {
    for (String a : new LinkedHashSet<>(of(args)))
        switch (a) {
            case "b" -> bat();
            case "f" -> fox();
        }
}

• Pascal

function HasOption(c: char): Boolean;
var
  i: integer;
begin
  Result := False;
  for i := 1 to ParamCount do
    if (ParamStr(i) = ('-' + c)) then Exit(True);
end;  

begin
  if HasOption('b') then Bat;
  if HasOption('f') then Fox;
end.

• Perl

for (@ARGV) {
    use experimental 'switch';
    bat when 'b';
    fox when 'f';
}

• Python

if 'b' in sys.argv[1:]: bat()
if 'f' in sys.argv[1:]: fox()

• Python

options = {
	'b': bat
	'f': fox
}

for option, function in options:
	if option in sys.argv[1:]:
		function()

• Ruby

bat if ARGV.include?("b")
fox if ARGV.include?("f")

• Rust

if let Some(arg) = ::std::env::args().nth(1) {
    if &arg == "f" {
        fox();
    } else if &arg = "b" {
        bat();
    } else {
	eprintln!("invalid argument: {}", arg),
    }
} else {
    eprintln!("missing argument");
}

• Rust

if let Some(arg) = ::std::env::args().nth(1) {
    match arg.as_str() {
        "f" => fox(),
        "b" => box(),
        _ => eprintln!("invalid argument: {}", arg),
    };
} else {
    eprintln!("missing argument");
}