Modulinos

It is useful to be able to run a main() function only when a program is run directly. This is a central feature in programming scripts; the feature is called /scripted main/.

Examples from GitHub.

C

C programs have scripted main by default; as long as main() is not included in the header file, this program's (empty) API is accessible by other C code.

<lang c>#include "scriptedmain.h"

include <stdio.h>
include <unistd.h>

int main(int argc, char **argv) { char cwd[1024]; getcwd(cwd, sizeof(cwd));

printf("Directory: %s\n", cwd);

printf("Program: %s\n", argv[0]);

printf("Number of Args: %d\n", argc);

int i; for (i = 0; i < argc; i++) { printf("Arg: %s\n", argv[i]); }

return 0; }</lang>

C++

C++ programs also have scripted main by default.

<lang cpp>#include <iostream>

include <unistd.h>

using namespace std;

int main(int argc, char **argv) { char cwd[1024]; getcwd(cwd, sizeof(cwd));

cout << "Directory: " << cwd << endl;

cout << "Program: " << argv[0] << endl;

cout << "Number of Args: " << argc << endl;

int i; for (i = 0; i < argc; i++) { cout << "Arg: " << argv[i] << endl; }

return 0; }</lang>

Erlang

Erlang programs also have scripted main by default.

<lang erlang>-module(scriptedmain). -import(lists, [map/2]).

main(Args) -> io:format("Directory: ~s~n", [filename:absname("")]), io:format("Program: ~s~n", [?FILE]), io:format("Number of Args: ~w~n", [length(Args)]), map (fun(Arg) -> io:format("Arg: ~s~n", [Arg]) end, Args).</lang>