How can I pass command-line arguments to a Erlang program?

Question

I'm working on a Erlang. How can I pass command line parameters to it?

Program File-

-module(program).
-export([main/0]).

main() ->
    io:fwrite("Hello, world!\n").

Compilation Command:

erlc Program.erl

Execution Command-

erl -noshell -s program main -s init stop

I need to pass arguments through execution command and want to access them inside main written in program's main.

Answer 1

$ cat program.erl
-module(program).
-export([main/1]).

main(Args) ->
    io:format("Args: ~p\n", [Args]).
$ erlc program.erl 
$ erl -noshell -s program main foo bar -s init stop
Args: [foo,bar]
$ erl -noshell -run program main foo bar -s init stop
Args: ["foo","bar"]

It is documented in erl man page.

I would recommend using escript for this purpose because it has a simpler invocation.

Answer 2

These are not really commandline-parameters, but if you want to use environment-variables, the os-module might help. os:getenv() gives you a list of all environment variables. os:getenv(Var) gives you the value of the variable as a string, or returns false if Var is not an environment-variable.

These env-variables should be set before you start the application.

I always use an idiom like this to start (on a bash-shell):

export PORT=8080 && erl -noshell -s program main