Modulinos
It is useful to be able to execute a main() function only when a program is run directly. This is a central feature in programming scripts. A script that behaves this way is called a modulino.
Examples from https://github.com/mcandre/modulinos
Sometimes getting the ScriptName is required in order to determine when to run main().
- This is still a draft task, and the current task description has caused mega confusion. See Talk:Modulinos for numerous attempts to understand the task and to rewrite the task description.
- The task Executable library is written to replace this task. This task's future is in doubt as its aims are not clear enough.
C
C programs cannot normally do scripted main, because main() is implicitly included by another program, test.c, even though scriptedmain.h omits any main() prototype. However, preprocessor instructions can hide main unless a compiler flag is explicitly set.
Example
<lang sh>$ make ./scriptedmain Main: The meaning of life is 42 ./test Test: The meaning of life is</lang>
Makefile
<lang make>all: scriptedmain test ./scriptedmain ./test
scriptedmain: scriptedmain.c scriptedmain.h gcc -o scriptedmain -DSCRIPTEDMAIN scriptedmain.c scriptedmain.h
test: test.c scriptedmain.h scriptedmain.c gcc -o test test.c scriptedmain.c scriptedmain.h
clean: -rm scriptedmain -rm test -rm scriptedmain.exe -rm test.exe</lang>
scriptedmain.h
<lang c>int meaning_of_life();</lang>
scriptedmain.c
<lang c>#include <stdio.h>
int meaning_of_life() { return 42; }
- ifdef SCRIPTEDMAIN
int main() { printf("Main: The meaning of life is %d\n", meaning_of_life());
return 0; }
- endif</lang>
test.c
<lang c>#include "scriptedmain.h"
- include <stdio.h>
extern int meaning_of_life();
int main(int argc, char **argv) { printf("Test: The meaning of life is %d\n", meaning_of_life()); return 0; }</lang>
C++
C++ programs cannot normally do scripted main, because main() is implicitly included by another program, test.c, even though scriptedmain.h omits any main() prototype. Preprocessor instructions can hide main() unless a compiler flat is explicitly set.
Example
<lang sh>$ make ./scriptedmain Main: The meaning of life is 42 ./test Test: The meaning of life is 42</lang>
Makefile
<lang make>all: scriptedmain test ./scriptedmain ./test
scriptedmain: scriptedmain.cpp scriptedmain.h g++ -o scriptedmain -static-libgcc -static-libstdc++ -DSCRIPTEDMAIN scriptedmain.cpp scriptedmain.h
test: test.cpp scriptedmain.h scriptedmain.cpp g++ -o test -static-libgcc -static-libstdc++ test.cpp scriptedmain.cpp scriptedmain.h
clean: -rm scriptedmain -rm test -rm scriptedmain.exe -rm test.exe</lang>
scriptedmain.h
<lang cpp>int meaning_of_life();</lang>
scriptedmain.cpp
<lang cpp>#include <iostream>
using namespace std;
int meaning_of_life() { return 42; }
- ifdef SCRIPTEDMAIN
int main() { cout << "Main: The meaning of life is " << meaning_of_life() << endl; return 0; }
- endif</lang>
test.cpp
<lang cpp>#include "scriptedmain.h"
- include <iostream>
using namespace std;
extern int meaning_of_life();
int main() { cout << "Test: The meaning of life is " << meaning_of_life() << endl; return 0; }</lang>
Clojure
Uses lein-exec.
scriptedmain.clj: <lang clojure>":";exec lein exec $0 ${1+"$@"} ":";exit
(ns scriptedmain
(:gen-class))
(defn meaning-of-life [] 42)
(defn -main [& args]
(println "Main: The meaning of life is" (meaning-of-life)))
(when (.contains (first *command-line-args*) *source-path*)
(apply -main (rest *command-line-args*)))</lang>
test.clj: <lang clojure>":";exec lein exec $0 ${1+"$@"} ":";exit
(ns test
(:gen-class))
(load-string (slurp "scriptedmain.clj"))
(defn -main [& args]
(println "Test: The meaning of life is" (scriptedmain/meaning-of-life)))
(when (.contains (first *command-line-args*) *source-path*)
(apply -main (rest *command-line-args*)))</lang>
CoffeeScript
scriptedmain.coffee: <lang coffeescript>#!/usr/bin/env coffee
meaningOfLife = () -> 42
exports.meaningOfLife = meaningOfLife
main = () ->
console.log "Main: The meaning of life is " + meaningOfLife()
if not module.parent then main()</lang>
test.coffee: <lang coffeescript>#!/usr/bin/env coffee
sm = require "./scriptedmain"
console.log "Test: The meaning of life is " + sm.meaningOfLife()</lang>
Common Lisp
Common Lisp has few standards for POSIX operation. Shebangs and command line arguments are hacks.
In CLISP, this code only works for ./scriptedmain.lisp.
~/.clisprc.lisp
<lang lisp>;;; Play nice with shebangs (set-dispatch-macro-character #\# #\!
(lambda (stream character n) (declare (ignore character n)) (read-line stream nil nil t) nil))</lang>
scriptedmain.lisp
<lang lisp>#!/bin/sh
- |
exec clisp -q -q $0 $0 ${1+"$@"} exit |#
- Usage
- ./scriptedmain.lisp
(defun meaning-of-life () 42)
(defun main (args)
(format t "Main: The meaning of life is ~a~%" (meaning-of-life)) (quit))
- With help from Francois-Rene Rideau
- http://tinyurl.com/cli-args
(let ((args
#+clisp ext:*args* #+sbcl sb-ext:*posix-argv* #+clozure (ccl::command-line-arguments) #+gcl si:*command-args* #+ecl (loop for i from 0 below (si:argc) collect (si:argv i)) #+cmu extensions:*command-line-strings* #+allegro (sys:command-line-arguments) #+lispworks sys:*line-arguments-list* ))
(if (member (pathname-name *load-truename*) args :test #'(lambda (x y) (search x y :test #'equalp))) (main args)))</lang>
test.lisp
<lang lisp>#!/bin/sh
- |
exec clisp -q -q $0 $0 ${1+"$@"} exit |#
(load "scriptedmain.lisp") (format t "Test: The meaning of life is ~a~%" (meaning-of-life))</lang>
D
D manages to implement scriptedmain through the use of version directives, which require special options to rdmd and dmd.
scriptedmain.d:
<lang d>#!/usr/bin/env rdmd -version=scriptedmain
module scriptedmain;
import std.stdio;
int meaningOfLife() { return 42; }
version (scriptedmain) { void main(string[] args) { writeln("Main: The meaning of life is ", meaningOfLife()); } }</lang>
test.d:
<lang d>#!/usr/bin/env rdmd -version=test
import scriptedmain; import std.stdio;
version (test) { void main(string[] args) { writeln("Test: The meaning of life is ", meaningOfLife()); } }</lang>
Example:
<lang sh>$ ./scriptedmain.d Main: The meaning of life is 42 $ ./test.d Test: The meaning of life is 42 $ dmd scriptedmain.d -version=scriptedmain $ ./scriptedmain Main: The meaning of life is 42 $ dmd test.d scriptedmain.d -version=test $ ./test Test: The meaning of life is 42</lang>
Dart
scriptedmain.dart: <lang dart>#!/usr/bin/env dart
- library("scriptedmain");
meaningOfLife() { return 42; }
main() { print("Main: The meaning of life is ${meaningOfLife()}"); }</lang>
test.dart: <lang dart>#!/usr/bin/env dart
- import("scriptedmain.dart", prefix: "scriptedmain");
main() { print("Test: The meaning of life is ${scriptedmain.meaningOfLife()}"); }</lang>
Example: <lang sh>$ ./scriptedmain.dart Main: The meaning of life is 42 $ ./test.dart Test: The meaning of life is 42</lang>
Emacs Lisp
Emacs has scripted main, though older versions require an obscure shebang syntax.
scriptedmain.el
<lang lisp>:;exec emacs -batch -l $0 -f main $*
- Shebang from John Swaby
- http://www.emacswiki.org/emacs/EmacsScripts
(defun meaning-of-life () 42)
(defun main ()
(message "Main: The meaning of life is %d" (meaning-of-life)))</lang>
test.el
<lang lisp>:;exec emacs -batch -l $0 -f main $*
- Shebang from John Swaby
- http://www.emacswiki.org/emacs/EmacsScripts
(defun main ()
(setq load-path (cons default-directory load-path)) (load "scriptedmain.el" nil t) (message "Test: The meaning of life is %d" (meaning-of-life)))</lang>
Erlang
Erlang has scripted main by default. scriptedmain.erl must be compiled before test.erl can access its functions.
Makefile: <lang make>all: t
t: scriptedmain.beam test.beam erl -noshell -s scriptedmain erl -noshell -s test
scriptedmain.beam: scriptedmain.erl erlc scriptedmain.erl
test.beam: test.erl erlc test.erl
clean: -rm *.beam</lang>
scriptedmain.erl: <lang erlang>-module(scriptedmain). -export([meaning_of_life/0, start/0]).
meaning_of_life() -> 42.
start() ->
io:format("Main: The meaning of life is ~w~n", [meaning_of_life()]), init:stop().</lang>
test.erl: <lang erlang>-module(test). -export([start/0]). -import(scriptedmain, [meaning_of_life/0]).
start() ->
io:format("Test: The meaning of life is ~w~n", [meaning_of_life()]), init:stop().</lang>
F#
Note 1: F# supports the scriptedmain behavior, but F# does not support hybrid script-compiled code files. The following programs work provided that they are compiled and then run, as .fs files, not interpreted or dotslashed as .fsx files.
Note 2: fsharpc has a backwards file ordering: Specify any dependencies BEFORE the code that depends on them.
Note 3: fsharpc also has that unpredictable DOS-flavored command line flag syntax, so the --out requires a colon between it and its value, and -h only generates an error; use --help instead.
Note 4: In Unix, mono is required to run F# executables. In Windows, mono is not required for execution.
Example:
<lang sh>$ make fsharpc --out:scriptedmain.exe ScriptedMain.fs fsharpc --out:test.exe ScriptedMain.fs Test.fs $ mono scriptedmain.exe Main: The meaning of life is 42 $ mono test.exe Test: The meaning of life is 42</lang>
Makefile:
<lang make>all: scriptedmain.exe test.exe
scriptedmain.exe: ScriptedMain.fs fsharpc --nologo --out:scriptedmain.exe ScriptedMain.fs
test.exe: Test.fs ScriptedMain.fs fsharpc --nologo --out:test.exe ScriptedMain.fs Test.fs
clean: -rm *.exe</lang>
ScriptedMain.fs:
<lang fsharp>namespace ScriptedMain
module ScriptedMain =
let meaningOfLife = 42
let main = printfn "Main: The meaning of life is %d" meaningOfLife</lang>
Test.fs:
<lang fsharp>module Test =
open ScriptedMain
let main = printfn "Test: The meaning of life is %d" ScriptedMain.meaningOfLife</lang>
Factor
Note: The INCLUDE/INCLUDING macros must be added to the ~/.factor-rc configuration file.
Example:
<lang sh>$ ./scriptedmain.factor Main: The meaning of life is 42 $ ./test.factor Test: The meaning of life is 42</lang>
~/.factor-rc:
<lang factor>! INCLUDING macro that imports source code files in the current directory
USING: kernel vocabs.loader parser sequences lexer vocabs.parser ; IN: syntax
- include-vocab ( vocab -- ) dup ".factor" append parse-file append use-vocab ;
SYNTAX: INCLUDING: ";" [ include-vocab ] each-token ;</lang>
scriptedmain.factor:
<lang factor>#! /usr/bin/env factor
USING: io math.parser ; IN: scriptedmain
- meaning-of-life ( -- n ) 42 ;
- main ( -- ) meaning-of-life "Main: The meaning of life is " write number>string print ;
MAIN: main</lang>
test.factor:
<lang factor>#! /usr/bin/env factor
INCLUDING: scriptedmain ; USING: io math.parser ; IN: test
- main ( -- ) meaning-of-life "Test: The meaning of life is " write number>string print ;
MAIN: main</lang>
Forth
Given this awful running reference:
<lang forth>42 constant Douglas-Adams
- go ( -- )
." The meaning of life is " Douglas-Adams . cr ;</lang>
The bulk of Forth systems provide a way to generate an executable that enters GO (ar any word) on start.
<lang forth>' go 'MAIN ! program douglas-adams</lang>
Which creates a file named 'douglas-adams' that you can then run. If this is all in the same file, you can load the file, test parts of it, and then exit (or shell out) to run the executable.
A unix script requires that '#!' be a comment and that the system have some #!-compatible arguments.
<lang forth>#! /usr/bin/env gforth
42 constant Douglas-Adams .( The meaning of life is ) Douglas-Adams . cr bye</lang>
Adding #! as a comment, as gforth does, is trivial. For a means by which this script could distinguish between 'scripted execution' and otherwise, a symlink like 'forthscript' could easily be used, and the zeroth OS argument tested for, but there's no convention.
<lang forth>#! /usr/bin/env forthscript
42 constant Douglas-Adams
s" forthscript" 0 arg compare 0= [IF]
.( The meaning of life is ) Douglas-Adams . cr bye
[THEN]
cr .( Why aren't you running this as a script? It only provides a constant.)</lang>
Groovy
Example:
<lang sh>$ ./ScriptedMain.groovy Main: The meaning of life is 42 $ ./Test.groovy Test: The meaning of life is 42</lang>
ScriptedMain.groovy:
<lang groovy>#!/usr/bin/env groovy
class ScriptedMain { static def meaningOfLife = 42
static main(args) { println "Main: The meaning of life is " + meaningOfLife } }</lang>
Test.groovy:
<lang groovy>#!/usr/bin/env groovy
println "Test: The meaning of life is " + ScriptedMain.meaningOfLife</lang>
Haskell
Haskell has scripted main, but getting scripted main to work with compiled scripts is tricky.
<lang sh>$ runhaskell scriptedmain.hs Main: The meaning of life is 42 $ runhaskell test.hs Test: The meaning of life is 42 $ ghc -fforce-recomp -o scriptedmain -main-is ScriptedMain scriptedmain.hs $ ./scriptedmain Main: The meaning of life is 42 $ ghc -fforce-recomp -o test -main-is Test test.hs scriptedmain.hs $ ./test Test: The meaning of life is 42</lang>
scriptedmain.hs
<lang haskell>#!/usr/bin/env runhaskell
-- Compile: -- -- ghc -fforce-recomp -o scriptedmain -main-is ScriptedMain scriptedmain.hs
module ScriptedMain where
meaningOfLife :: Int meaningOfLife = 42
main :: IO () main = putStrLn $ "Main: The meaning of life is " ++ show meaningOfLife</lang>
test.hs
<lang haskell>#!/usr/bin/env runhaskell
-- Compile: -- -- ghc -fforce-recomp -o test -main-is Test test.hs scriptedmain.hs
module Test where
import ScriptedMain hiding (main)
main :: IO () main = putStrLn $ "Test: The meaning of life is " ++ show meaningOfLife</lang>
Io
ScriptedMain.io:
<lang io>#!/usr/bin/env io
ScriptedMain := Object clone ScriptedMain meaningOfLife := 42
if( isLaunchScript,
"Main: The meaning of life is #{ScriptedMain meaningOfLife}" interpolate println
)</lang>
test.io:
<lang io>#!/usr/bin/env io
"Test: The meaning of life is #{ScriptedMain meaningOfLife}" interpolate println</lang>
<lang sh>$ ./ScriptedMain.io Main: The meaning of life is 42 $ ./test.io Test: The meaning of life is 42</lang>
J
modulinos.ijs:
<lang j>#!/usr/bin/env ijconsole
meaningOfLife =: 42
main =: monad define echo 'Main: The meaning of life is ',": meaningOfLife exit )
shouldrun =: monad define if. 1 e. 'modulinos.ijs' E. ;ARGV do. main 0 end. )
shouldrun 0</lang>
test.j:
<lang j>#!/usr/bin/env jconsole
load 'modulinos.ijs'
echo 'Test: The meaning of life is ',": meaningOfLife
exit </lang>
Example:
<lang sh>$ ./modulinos.ijs Main: The meaning of life is 42 $ ./test.j Test: The meaning of life is 42</lang>
Java
Java has scripted main by default.
ScriptedMain.java
<lang java>public class ScriptedMain { public static int meaningOfLife() { return 42; }
public static void main(String[] args) { System.out.println("Main: The meaning of life is " + meaningOfLife()); } }</lang>
Test.java
<lang java>public class Test { public static void main(String[] args) { System.out.println("Test: The meaning of life is " + ScriptedMain.meaningOfLife()); } }</lang>
JavaScript
Node.js has scripted main.
scriptedmain.js <lang javascript>#!/usr/bin/env node
function meaningOfLife() { return 42; }
exports.meaningOfLife = meaningOfLife;
function main() { console.log("Main: The meaning of life is " + meaningOfLife()); }
if (!module.parent) { main(); }</lang>
test.js <lang javascript>#!/usr/bin/env node
var sm = require("./scriptedmain");
console.log("Test: The meaning of life is " + sm.meaningOfLife());</lang>
LLVM
LLVM can have scripted main a la C, using the weak attribute.
<lang sh>$ make llvm-as scriptedmain.ll llc scriptedmain.bc gcc -o scriptedmain scriptedmain.s ./scriptedmain Main: The meaning of life is 42 llvm-as test.ll llc test.bc gcc -o test test.s scriptedmain.s ./test Test: The meaning of life is 42</lang>
Makefile
<lang make>EXECUTABLE_SM=scriptedmain EXECUTABLE_TEST=test
all: test.ll scriptedmain.s llvm-as test.ll llc test.bc gcc -o $(EXECUTABLE_TEST) test.s scriptedmain.s ./$(EXECUTABLE_TEST)
scriptedmain.s: scriptedmain.ll llvm-as scriptedmain.ll llc scriptedmain.bc gcc -o $(EXECUTABLE_SM) scriptedmain.s ./$(EXECUTABLE_SM)
clean: -rm $(EXECUTABLE_TEST) -rm $(EXECUTABLE_SM) -rm test.s -rm test.bc -rm scriptedmain.s -rm scriptedmain.bc</lang>
scriptedmain.ll
<lang llvm>@msg_main = internal constant [33 x i8] c"Main: The meaning of life is %d\0A\00"
declare i32 @printf(i8* noalias nocapture, ...)
define i32 @meaning_of_life() { ret i32 42 }
define weak i32 @main(i32 %argc, i8** %argv) { %meaning = call i32 @meaning_of_life()
call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([33 x i8]* @msg_main, i32 0, i32 0), i32 %meaning)
ret i32 0 }</lang>
test.ll
<lang llvm>@msg_test = internal constant [33 x i8] c"Test: The meaning of life is %d\0A\00"
declare i32 @printf(i8* noalias nocapture, ...)
declare i32 @meaning_of_life()
define i32 @main(i32 %argc, i8** %argv) { %meaning = call i32 @meaning_of_life()
call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([33 x i8]* @msg_test, i32 0, i32 0), i32 %meaning)
ret i32 0 }</lang>
Lua
Lua has scripted main by default because files are largely indistinguishable from functions semantically (they compile to Lua functions.) Ellipses is Lua's var-arg syntax for functions, and, therefore, for files as well.
scriptedmain.lua
<lang lua>#!/usr/bin/env lua
function meaningoflife() return 42 end
function main(arg) print("Main: The meaning of life is " .. meaningoflife()) end
if type(package.loaded[(...)]) ~= "userdata" then main(arg) else module(..., package.seeall) end</lang>
test.lua
<lang lua>#!/usr/bin/env lua sm = require("scriptedmain") print("Test: The meaning of life is " .. sm.meaningoflife())</lang>
Make
Example <lang sh>$ make -f scriptedmain.mf The meaning of life is 42 (Main) $ make -f test.mf The meaning of life is 42 (Test)</lang>
scriptedmain.mf <lang make>all: scriptedmain
meaning-of-life: @echo "The meaning of life is 42"
scriptedmain: meaning-of-life @echo "(Main)" </lang>
test.mf <lang make>all: test
test: @make -f scriptedmain.mf meaning-of-life @echo "(Test)" </lang>
Mathematica
scriptedmain.ma <lang mathematica>#!/usr/bin/env MathKernel -script
MeaningOfLife[] = 42
ScriptName[] = Piecewise[ { {"Interpreted", Position[$CommandLine, "-script", 1] == {}} }, $CommandLine[[Position[$CommandLine, "-script", 1]1,1 + 1]] ]
Program = ScriptName[];
If[StringMatchQ[Program, ".*scriptedmain.*"], Print["Main: The meaning of life is " <> ToString[MeaningOfLife[]]] ]</lang>
test.ma: <lang mathematica>#!/usr/bin/env MathKernel -script
Get["scriptedmain.ma"]
Print["Test: The meaning of life is " <> ToString[MeaningOfLife[]]]</lang>
Example: <lang sh>$ ./scriptedmain.ma Main: The meaning of life is 42 $ ./test.ma Test: The meaning of life is 42</lang>
In Mac and Windows, the output will be surrounded by spurious quotes.
Mozart/Oz
Makefile: <lang make>all: run
run: scriptedmain test ./scriptedmain ./test
scriptedmain: scriptedmain.oz ozc -x scriptedmain.oz
scriptedmain.ozf: scriptedmain.oz ozc -c scriptedmain.oz
test: scriptedmain.ozf test.oz ozc -x test.oz
clean: -rm test -rm scriptedmain -rm *.ozf -rm *.exe </lang>
scriptedmain.oz: <lang oz>functor export
meaningOfLife: MeaningOfLife
import
System Application Property Regex at 'x-oz://contrib/regex'
define
fun {MeaningOfLife} 42 end
local ScriptName = {Property.get 'application.url'} in if {Regex.search "scriptedmain" ScriptName} \= false then {System.printInfo "Main: The meaning of life is "#{Int.toString {MeaningOfLife}}#"\n"} {Application.exit 0} end end
end </lang>
test.oz: <lang oz>functor import
ScriptedMain System Application Property Regex at 'x-oz://contrib/regex'
define
local ScriptName = {Property.get 'application.url'} in if {Regex.search "test" ScriptName} \= false then {System.printInfo "Test: The meaning of life is "#{Int.toString {ScriptedMain.meaningOfLife}}#"\n"} {Application.exit 0} end end
end</lang>
newLISP
newLISP lacks scripted main, but the feature is easily added.
scriptedmain.lsp
<lang lisp>#!/usr/bin/env newlisp
(context 'SM)
(define (SM:meaning-of-life) 42)
(define (main) (println (format "Main: The meaning of life is %d" (meaning-of-life))) (exit))
(if (find "scriptedmain" (main-args 1)) (main))
(context MAIN)</lang>
test.lsp
<lang lisp>#!/usr/bin/env newlisp
(load "scriptedmain.lsp") (println (format "Test: The meaning of life is %d" (SM:meaning-of-life))) (exit)</lang>
Objective-C
scriptedmain.h:
<lang objc>#import <objc/Object.h>
@interface ScriptedMain: Object {}
+ (int)meaningOfLife;
@end</lang>
scriptedmain.m:
<lang objc>#import "scriptedmain.h"
- import <Foundation/Foundation.h>
@implementation ScriptedMain
+ (int)meaningOfLife { return 42; }
@end
int __attribute__((weak)) main(int argc, char **argv) { @autoreleasepool {
printf("Main: The meaning of life is %d\n", [ScriptedMain meaningOfLife]);
}
return 0; }</lang>
test.m:
<lang objc>#import "scriptedmain.h"
- import <Foundation/Foundation.h>
int main(int argc, char **argv) { @autoreleasepool {
printf("Test: The meaning of life is %d\n", [ScriptedMain meaningOfLife]);
}
return 0; }</lang>
<lang sh>$ gcc -o scriptedmain -lobjc -framework foundation scriptedmain.m $ gcc -o test -lobjc -framework foundation test.m scriptedmain.m $ ./scriptedmain Main: The meaning of life is 42 $ ./test Test: The meaning of life is 42</lang>
OCaml
scriptedmain.ml
<lang ocaml>let meaning_of_life = 42
let main () =
Printf.printf "Main: The meaning of life is %d\n" meaning_of_life
let () =
if not !Sys.interactive then main ()</lang>
Invoked as a script:
<lang sh>$ ocaml scriptedmain.ml Main: The meaning of life is 42</lang>
Loaded into an ocaml toplevel/utop:
<lang>$ ocaml ...
- #use "scriptedmain.ml";;
val meaning_of_life : int = 42 val main : unit -> unit = <fun>
- meaning_of_life;;
- : int = 42
- </lang>
The limit of this technique is "avoiding running something when loading a script interactively". It's not applicable to other uses, like adding an example script to a file normally used as a library, as that code will also fire when users of the library are run.
Octave/MATLAB
Octave and MATLAB have scripted main by default, because only the first function listed in a program are importable by other programs.
meaningoflife.m
<lang matlab>#!/usr/bin/env octave -qf
function y = meaningoflife() y = 42; endfunction
function main() printf("Main: The meaning of life is %d", meaningoflife()); endfunction
main();</lang>
test.m
<lang matlab>#!/usr/bin/env octave -qf
printf("Test: The meaning of life is %d", meaningoflife());</lang>
Pascal
Makefile:
<lang make>all: scriptedmain
scriptedmain: scriptedmain.pas fpc -dscriptedmain scriptedmain.pas
test: test.pas scriptedmain fpc test.pas
clean: -rm test -rm scriptedmain -rm *.o -rm *.ppu</lang>
scriptedmain.pas:
<lang pascal>{$IFDEF scriptedmain} program ScriptedMain; {$ELSE} unit ScriptedMain; interface function MeaningOfLife () : integer; implementation {$ENDIF} function MeaningOfLife () : integer; begin MeaningOfLife := 42 end; {$IFDEF scriptedmain} begin write('Main: The meaning of life is: '); writeln(MeaningOfLife()) {$ENDIF} end.</lang>
test.pas:
<lang pascal>program Test; uses ScriptedMain; begin write('Test: The meaning of life is: '); writeln(MeaningOfLife()) end.</lang>
Example:
<lang sh>$ make $ ./scriptedmain Main: The meaning of life is: 42 $ make test $ ./test Test: The meaning of life is: 42</lang>
Perl
Perl has scripted main. The code inside unless(caller) { ... } only runs when Life.pm is the main program.
<lang perl>#!/usr/bin/env perl
- Life.pm
package Life;
use strict; use warnings;
sub meaning_of_life { return 42; }
unless(caller) { print "Main: The meaning of life is " . meaning_of_life() . "\n"; }</lang>
<lang perl>#!/usr/bin/env perl
- death.pl
use strict; use warnings;
use Life;
print "Life means " . Life::meaning_of_life . ".\n"; print "Death means invisible scary skeletons.\n";</lang>
Perl 6
Perl 6 automatically calls MAIN on direct invocation, but this may be a multi dispatch, so a library may have multiple "scripted mains". <lang perl6>class LUE {
has $.answer = 42;
}
multi MAIN ('test') {
say "ok" if LUE.new.answer == 42;
}
multi MAIN ('methods') {
say ~LUE.^methods;
}</lang>
Phix
Here is a simple little dirty hack to do this. You can put the function in any file, but you have to call it from the right place. <lang Phix>function isMainOrInclude() -- returns 1 if called from the main file, 0 if from an include integer res
#ilASM{ [32] mov eax,[ebp+20] -- prev_ebp mov eax,[eax+8] -- rtn mov [res],eax [64] mov rax,[rbp+40] -- prev_ebp mov rax,[rax+16] -- rtn mov [res],rax [] } return res=21 -- (21=T_maintls)
end function
printf(1,"This is %s\n",{{"An Include","Main"}[isMainOrInclude()+1]})</lang>
PHP
PHP does not have scripted main, but the feature is easily added with a regular expression.
scriptedmain.php
<lang php><?php function meaning_of_life() { return 42; }
function main($args) { echo "Main: The meaning of life is " . meaning_of_life() . "\n"; }
if (preg_match("/scriptedmain/", $_SERVER["SCRIPT_NAME"])) { main($argv); } ?></lang>
test.php
<lang php><?php require_once("scriptedmain.php"); echo "Test: The meaning of life is " . meaning_of_life() . "\n"; ?></lang>
PicoLisp
PicoLisp normally does it the other way round: It calls main from the command line with the '-' syntax if desired. Create an executable file (chmod +x) "life.l": <lang PicoLisp>#!/usr/bin/picolisp /usr/lib/picolisp/lib.l
(de meaningOfLife ()
42 )
(de lifemain ()
(prinl "Main: The meaning of life is " (meaningOfLife)) (bye) )</lang>
and an executable file (chmod +x) "test.l": <lang PicoLisp>#!/usr/bin/picolisp /usr/lib/picolisp/lib.l
(load "life.l")
(prinl "Test: The meaning of life is " (meaningOfLife)) (bye)</lang> Test:
$ ./life.l -lifemain Main: The meaning of life is 42 $ ./test.l Test: The meaning of life is 42
Python
Python has scripted main.
<lang python>#!/usr/bin/env python
- life.py
def meaning_of_life():
return 42
if __name__ == "__main__":
print("Main: The meaning of life is %s" % meaning_of_life())</lang>
<lang python>#!/usr/bin/env python
- death.py
from life import meaning_of_life
print("Life means %s." % meaning_of_life()) print("Death means invisible scary skeletons.")</lang>
R
A way to check if code is running at "top level" is to check length(sys.frames())
. This value will be zero for a file being run with Rscript
, the --file=
argument, or at the command line, and will be greater than 0 in all other conditions (such as package loading or code being sourced from another file.)
<lang R>#!/usr/bin/env Rscript
meaningOfLife <- function() { 42 }
main <- function(args) { cat("Main: The meaning of life is", meaningOfLife(), "\n") }
if (length(sys.frames()) > 0) {
args <- commandArgs(trailingOnly = FALSE)
main(args) q("no") }</lang>
test.R
<lang R>#!/usr/bin/env Rscript
source("scriptedmain.R")
cat("Test: The meaning of life is", meaningOfLife(), "\n")
q("no")</lang>
Racket
scriptedmain.rkt: <lang racket>#!/usr/bin/env racket
- lang racket
(provide meaning-of-life)
(define (meaning-of-life) 42)
(module+ main (printf "Main: The meaning of life is ~a\n" (meaning-of-life)))</lang>
test.rkt: <lang racket>#!/usr/bin/env racket
- lang racket
(module+ main (require "scriptedmain.rkt") (printf "Test: The meaning of life is ~a\n" (meaning-of-life)))</lang>
REXX
<lang rexx>/*REXX program detects whether or not it is a "scripted main" program. */ parse source . howInvoked . /*ask REXX how we got invoked.*/ if howInvoked \== "COMMAND" then exit 0 /*if not a COMMAND, just exit.*/
/* ╔════════════════════════════════════════════════════════════╗ ║ At this point, we know that this program was invoked via ║ ║ the "command line" and not via another program. ║ ╚════════════════════════════════════════════════════════════╝ */
say 'and away we go ···'</lang> Note: Actually another program can invoke the above (ma.rex) as a command: <lang rexx>'rexx ma'</lang>
Ring
<lang ring>
- Project : Modulinos
- Date : 2017/12/23
- Author : Gal Zsolt (~ CalmoSoft ~)
- Email : <calmosoft@gmail.com>
func meaningoflife()
y = 42 return y
func main()
see "Main: The meaning of life is " + meaningoflife() + nl
</lang> Output:
Main: The meaning of life is 42
Ruby
Ruby has scripted main.
<lang ruby># life.rb
def meaning_of_life
42
end
if __FILE__ == $0
puts "Main: The meaning of life is #{meaning_of_life}"
end</lang>
<lang ruby># death.rb
require 'life'
puts "Life means #{meaning_of_life}." puts "Death means invisible scary skeletons."</lang>
Rust
Note: this code is deprecated, and does not compile with Rust 1.0.0 and newer.
Makefile: <lang make>all: scriptedmain
scriptedmain: scriptedmain.rs rustc scriptedmain.rs
test: test.rs scriptedmain.rs rustc --lib scriptedmain.rs rustc test.rs -L .
clean: -rm test -rm -rf *.dylib -rm scriptedmain -rm -rf *.dSYM</lang>
scriptedmain.rs: <lang rust>#[link(name = "scriptedmain")];
use std;
fn meaning_of_life() -> int { ret 42; }
fn main() { std::io::println("Main: The meaning of life is " + core::int::to_str(meaning_of_life(), 10u)); }</lang>
test.rs: <lang rust>use scriptedmain; use std;
fn main() { std::io::println("Test: The meaning of life is " + core::int::to_str(scriptedmain::meaning_of_life(), 10u)); }</lang>
Example: <lang sh>$ make $ make test $ ./scriptedmain Main: The meaning of life is 42 $ ./test Test: The meaning of life is 42</lang>
SAC
Makefile: <lang make>all: scriptedmain
scriptedmain: ScriptedMain.sac sac2c -o scriptedmain ScriptedMain.sac -Dscriptedmain
test: test.sac ScriptedMain.sac sac2c ScriptedMain.sac sac2c -o test test.sac
clean: -rm test -rm test.c -rm libScriptedMainTree.so -rm libScriptedMainMod.so -rm libScriptedMainMod.a -rm scriptedmain -rm scriptedmain.c</lang>
ScriptedMain.sac: <lang c>#ifndef scriptedmain module ScriptedMain;
- endif
use StdIO: all; use Array: all; export all;
int meaning_of_life() { return(42); }
- ifdef scriptedmain
int main() { printf("Main: The meaning of life is %d\n", meaning_of_life()); return(0); }
- endif</lang>
test.sac: <lang c>use StdIO: all; use Array: all; use ScriptedMain: all;
int main() { printf("Test: The meaning of life is %d\n", meaning_of_life()); return(0); }</lang>
Example: <lang sh>$ make $ make test $ ./scriptedmain Main: The meaning of life is 42 $ ./test Test: The meaning of life is 42</lang>
Scala
Unix shell script
This code must be stored as a shell script. <lang bash>#!/bin/sh exec scala "$0" "$@" !#
def hailstone(n: Int): Stream[Int] = n #:: (if (n == 1) Stream.empty else hailstone(if (n % 2 == 0) n / 2 else n * 3 + 1))
val nr = argv.headOption.map(_.toInt).getOrElse(27) val collatz = hailstone(nr) println(s"Use the routine to show that the hailstone sequence for the number: $nr.") println(collatz.toList) println(s"It has ${collatz.length} elements.")</lang>
Windows Command Script
This code must be stored as a Windows Command Script e.g. Hailstone.cmd <lang winbatch>::#! @echo off call scala %0 %* pause goto :eof
- !#
def hailstone(n: Int): Stream[Int] = n #:: (if (n == 1) Stream.empty else hailstone(if (n % 2 == 0) n / 2 else n * 3 + 1))
val nr = argv.headOption.map(_.toInt).getOrElse(27) val collatz = hailstone(nr) println(s"Use the routine to show that the hailstone sequence for the number: $nr.") println(collatz.toList) println(s"It has ${collatz.length} elements.")
</lang>
- Output:
C:\>Hailstone.cmd 42 Use the routine to show that the hailstone sequence for the number: 42. List(42, 21, 64, 32, 16, 8, 4, 2, 1) It has 9 elements.
Scheme
Chicken Scheme has the {{{ -ss }}} flag for the interpreter, but compiled Chicken Scheme programs do not have scripted main unless the behavior is added manually to the code.
scriptedmain.scm
<lang scheme>#!/bin/sh
- |
exec csi -ss $0 ${1+"$@"} exit |#
(use posix) (require-extension srfi-1) ; lists
(define (meaning-of-life) 42)
(define (main args) (display (format "Main: The meaning of life is ~a\n" (meaning-of-life))) (exit))
(define (program) (if (string=? (car (argv)) "csi") (let ((s-index (list-index (lambda (x) (string-contains x "-s")) (argv)))) (if (number? s-index) (cons 'interpreted (list-ref (argv) (+ 1 s-index))) (cons 'unknown ""))) (cons 'compiled (car (argv)))))
(if (equal? (car (program)) 'compiled) (main (cdr (argv))))</lang>
test.scm
<lang scheme>#!/bin/sh
- |
exec csi -ss $0 ${1+"$@"} exit |# (define (main args) (load "scriptedmain.scm") (display (format "Test: The meaning of life is ~a\n" (meaning-of-life))) (exit))</lang>
Smalltalk
Note that the ScriptedMain package must be installed in order for test.st to access code from scriptedmain.st.
Example
<lang shell>$ gst-package -t ~/.st package.xml &>/dev/null
$ ./scriptedmain.st Main: The meaning of life is 42
$ ./test.st Test: The meaning of life is 42</lang>
package.xml
<lang xml><packages> <package> <name>ScriptedMain</name> <filein>scriptedmain.st</filein> <file>scriptedmain.st</file> </package> </packages></lang>
scriptedmain.st
<lang smalltalk>"exec" "gst" "-f" "$0" "$0" "$@" "exit"
Object subclass: ScriptedMain [ ScriptedMain class >> meaningOfLife [ ^42 ] ]
| main |
main := [ Transcript show: 'Main: The meaning of life is ', ((ScriptedMain meaningOfLife) printString); cr. ].
(((Smalltalk getArgc) > 0) and: [ ((Smalltalk getArgv: 1) endsWith: 'scriptedmain.st') ]) ifTrue: [ main value. ].</lang>
test.st
<lang smalltalk>"exec" "gst" "-f" "$0" "$0" "$@" "exit"
" PackageLoader fileInPackage: 'ScriptedMain'.
Transcript show: 'Test: The meaning of life is ', ((ScriptedMain meaningOfLife) printString); cr.</lang>
Swift
Swift requires a number of hacks and boilerplate, but it is possible to write a modulino nevertheless.
Example
<lang shell>$ make mkdir -p bin/ swiftc -D SCRIPTEDMAIN -o bin/ScriptedMain ScriptedMain.swift swiftc -emit-library -module-name ScriptedMain -emit-module ScriptedMain.swift mkdir -p bin/ swiftc -D TEST -o bin/Test Test.swift -I "." -L "." -lScriptedMain -module-link-name ScriptedMain bin/ScriptedMain Main: The meaning of life is 42 bin/Test Test: The meaning of life is 42</lang>
Makefile
<lang make>all: bin/ScriptedMain bin/Test bin/ScriptedMain bin/Test
bin/ScriptedMain: ScriptedMain.swift mkdir -p bin/ swiftc -D SCRIPTEDMAIN -o bin/ScriptedMain ScriptedMain.swift
ScriptedMain.swiftmodule: ScriptedMain.swift swiftc -emit-library -module-name ScriptedMain -emit-module ScriptedMain.swift
bin/Test: Test.swift ScriptedMain.swiftmodule mkdir -p bin/ swiftc -D TEST -o bin/Test Test.swift -I "." -L "." -lScriptedMain -module-link-name ScriptedMain
clean: -rm -rf bin/ -rm *.swiftmodule -rm *.swiftdoc -rm *.dylib </lang>
ScriptedMain.swift
<lang swift>import Foundation
public class ScriptedMain {
public var meaningOfLife = 42
public init() {}
public class func main() { var meaning = ScriptedMain().meaningOfLife
println("Main: The meaning of life is \(meaning)") }
}
- if SCRIPTEDMAIN
@objc class ScriptedMainAutoload {
@objc class func load() { ScriptedMain.main() }
}
- endif
</lang>
Test.swift
<lang swift>import Foundation import ScriptedMain
public class Test {
public class func main() { var meaning = ScriptedMain().meaningOfLife
println("Test: The meaning of life is \(meaning)") }
}
- if TEST
@objc class TestAutoload {
@objc class func load() { Test.main() }
}
- endif
</lang>
Tcl
<lang tcl>proc main {args} {
puts "Directory: [pwd]" puts "Program: $::argv0" puts "Number of args: [llength $args]" foreach arg $args {puts "Arg: $arg"}
}
if {$::argv0 eq [info script]} {
main {*}$::argv
}</lang>
UNIX Shell
Bash has scripted main.
scriptedmain.sh
<lang sh>#!/usr/bin/env sh
meaning_of_life() { return 42 }
main() { meaning_of_life echo "Main: The meaning of life is $?" }
if "$BASH_SOURCE" == "$0" then
main
fi</lang>
test.sh
<lang sh>#!/bin/bash
path=$(dirname -- "$0") source "$path/scriptedmain"
meaning_of_life echo "Test: The meaning of life is $?" </lang>
ZX Spectrum Basic
On the ZX Spectrum, there is no main function as such, however a saved program can be made to start running from a particular line number by providing the line number as a parameter to save command. If the program is being merged as a module, then it does not run automatically. The following example will save the program in memory so that it starts running from line 500:
<lang zxbasic>SAVE "MYPROG" LINE 500: REM For a program with main code starting at line 500</lang>
- Draft Programming Tasks
- Basic language learning
- C
- C++
- Clojure
- CoffeeScript
- Common Lisp
- D
- Dart
- Emacs Lisp
- Erlang
- F Sharp
- Factor
- Forth
- Groovy
- Haskell
- Io
- J
- Java
- JavaScript
- LLVM
- Lua
- Make
- Mathematica
- Mozart/Oz
- NewLISP
- Objective-C
- OCaml
- Octave
- MATLAB
- Pascal
- Perl
- Perl 6
- Phix
- PHP
- PicoLisp
- Python
- R
- Racket
- REXX
- Ring
- Ruby
- Rust
- SAC
- Scala
- Scheme
- Smalltalk
- Swift
- Tcl
- UNIX Shell
- ZX Spectrum Basic
- Ada/Omit
- Go/Omit