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erlang.md

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Startup

erl

launches a shell, which is a vm, which is a node

Shut down a shell

  1. Control+\
  2. halt()

Comments

% Begin with a percent
% Continue to the end of the line
% There are no multiline comments

Shut down a shell cleanly

init:stop()

File system nav

cd().
ls().
pwd().

Compile

c("some file name.erl").

Run a function

The format is namespace:functionName(args).

io:fwrite("hello, world\n").

Functions

  • start with an ->
  • end with a .
  • statements are seperated by a ,
  • statements with multiple clauses seperate them with a ;
  • statements with multiple clauses do not put anything after the last clause

Clear shell variables

f().

Pid ! is fire and forget

Is this what they call naked banging?

Loading an erl

  • code is loaded from the codepath, .erl files in the cd of the repl will be found automatically

Running a function from a module

  • can be done by entering the following: module:exportedFunctionName().

Lists active erl nodes

nodes().

RPC

  • remote pricedure call, run something on a remote node

spawn()

  • will start a new processs, optionally on a remote node
  • Erlang processes are isolated

List comprehension

[X || X <- lists:seq(1,10)].

produces [1,2,3,4,5,6,7,8,9,10]

[X*2 || X <- lists:seq(1,10)].

produces [1,2,3,4,5,6,7,8,9,10]

Command Line docs:

http://erlang.org/doc/man/erl.html

API Docs

http://erldocs.com/R15B/

Opening new nodes

From the terminal: erl -sname someNodeName

  • this will launch a node with a repl and will report it's 'name' as someNodeName@hostname

Detecting other Nodes

nodes().
  • will probably return an empty list
  • []

Connecting to other nodes

net_adm:ping(nodeName@hostName).
  • should respond with pong
  • if there are special characters in the name you'll need to warp it in ticks, tech. the problem is that this isn't a valid atom name net_adm:ping('dog@host').
  • might have a problem connecting from sublime because it doesn't have a name
  • fixed this by updating /Users/username/Library/Application Support/Sublime Text 2/Packages/SublimeREPL/config/Erlang/Main.sublime-menu

Load a module (a compiled module) on all connected nodes

nl(modulename).

#Start a module on a remote node spawn('nodeName@hostname', module, function, args). e.g. spawn('dog@salad', atm, stop, []).

  • will return the erlang pid of the process

Stop all atms on connected nodes (does not include the current node)

[spawn(X, atm, stop, []) || X <- nodes()].

Stop all atms on connected nodes including the current node)

[spawn(X, atm, stop, []) || X <- nodes()++[node()]].

lrrad