Program name

Program name is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

It is useful to programmatically access a program's name, e.g. for determining whether the user ran "python hello.py", or "python hellocaller.py", a program importing the code from "hello.py".

Examples from GitHub.

C

It might not be very useful for a C program to access source filenames, because C code must be compiled into an executable, and anything could have happened to the source file after the compilation. However, C can access the executable's filename.

<lang c>#include <stdio.h>

int main(int argc, char **argv) { printf("Executable: %s\n", argv[0]);

return 0; }</lang>

To get the source information about some part of code, use compiler defined macros. Most compilers support them or some variation of. <lang c>#include <stdio.h>

int main() { printf("This code was in file %s in function %s, at line %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; }</lang>

C++

C++ has difficulty accessing source code filenames, because C code must be compiled into an executable. However, C++ can access the executable's filename.

<lang cpp>#include <iostream>

using namespace std;

int main(int argc, char **argv) { char *program = argv[0]; cout << "Program: " << program << endl;

return 0; }</lang>

Erlang

Erlang's macros hold information about the running module.

<lang erlang>-module(scriptname).

main(_) -> Program = ?FILE, io:format("Program: ~s~n", [Program]).</lang>

Haskell

Haskell has an impure function for this.

<lang haskell>#!/usr/bin/env runhaskell

module ScriptName where

import System (getProgName)

main :: IO () main = do program <- getProgName putStrLn $ "Program: " ++ program</lang>

Java

Java mainly has notions of classes.

<lang java>public class ScriptName { public static void main(String[] args) { String program = new ScriptName().getClass().getName(); System.out.println("Program: " + program); } }</lang>

Lua

Lua's arg is like C's argv.

<lang lua>#!/usr/bin/env lua

function main(arg) local program = arg[0] print("Program: " .. program) end

if type(package.loaded[(...)]) ~= "userdata" then main(arg) else module(..., package.seeall) end</lang>

newLISP

newLISP has a function, (main-args int) for this.

<lang lisp>#!/usr/bin/env newlisp

(let ((program (main-args 1)))

 (println (format "Program: %s" program))
 (exit))</lang>

Node.js

Node.js has a global variable for this.

<lang javascript>#!/usr/bin/env node /*jslint nodejs:true */

function main() { var program = __filename; console.log("Program: " + program); }

if (!module.parent) { main(); }</lang>

Perl 5

<lang perl>#!/usr/bin/env perl

use strict; use warnings;

sub main { my $program = $0; print "Program: $program\n"; }

unless(caller) { main; }</lang>

Perl 6

In Perl 6, the name of the program being executed is in the special global variable $*PROGRAM_NAME. <lang perl6>say $*PROGRAM_NAME;</lang>

PHP

PHP has a global dictionary for this.

<lang php><?php $program = $_SERVER["SCRIPT_NAME"]; echo "Program: $program\n"; ?></lang>

Python

<lang python>#!/usr/bin/env python

import inspect

def main(): program = inspect.getfile(inspect.currentframe()) print "Program: %s" % program

if __name__=="__main__": main()</lang>

R

R's syntax is complicated, but doable.

<lang R>#!/usr/bin/env Rscript

getProgram <- function(args) { sub("--file=", "", args[grep("--file=", args)]) }

args <- commandArgs(trailingOnly = FALSE) program <- getProgram(args)

cat("Program: ", program, "\n")

q("no")</lang>