-module(hello_world). %% 模块声明
-export([hello/0]).   %% 公共函数声明,相当于java的public，其他模块可以调用
hello() ->
	io:format("Hello World!\n"). 

➜ erl
Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:4:4] [async-threads:0] [kernel-poll:false]
Eshell V5.9.1  (abort with ^G)
1> c(hello_world).
{ok,hello_world}
2> rr(hello_world).
[]
3> hello_world:hello().
Hello World!
ok
4> 

c(module). %% 编译模块
rr(module). %% 加载模块
module:fun(). %% 调用模块下的函数
f(). – forget all variables (解绑所以变量)
f(X). – forget X (解绑变量X)

➜  ~  erl
Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:4:4] [async-threads:0] [kernel-poll:false]

Eshell V5.9.1  (abort with ^G)
1> help().
** shell internal commands **
b()        -- display all variable bindings
e(N)       -- repeat the expression in query <N>
f()        -- forget all variable bindings
f(X)       -- forget the binding of variable X
h()        -- history
history(N) -- set how many previous commands to keep
results(N) -- set how many previous command results to keep
catch_exception(B) -- how exceptions are handled
v(N)       -- use the value of query <N>
rd(R,D)    -- define a record
rf()       -- remove all record information
rf(R)      -- remove record information about R
rl()       -- display all record information
rl(R)      -- display record information about R
rp(Term)   -- display Term using the shell's record information
rr(File)   -- read record information from File (wildcards allowed)
rr(F,R)    -- read selected record information from file(s)
rr(F,R,O)  -- read selected record information with options
** commands in module c **
bt(Pid)    -- stack backtrace for a process
c(File)    -- compile and load code in <File>
cd(Dir)    -- change working directory
flush()    -- flush any messages sent to the shell
help()     -- help info
i()        -- information about the system
ni()       -- information about the networked system
i(X,Y,Z)   -- information about pid <X,Y,Z>
l(Module)  -- load or reload module
lc([File]) -- compile a list of Erlang modules
ls()       -- list files in the current directory
ls(Dir)    -- list files in directory <Dir>
m()        -- which modules are loaded
m(Mod)     -- information about module <Mod>
memory()   -- memory allocation information
memory(T)  -- memory allocation information of type <T>
nc(File)   -- compile and load code in <File> on all nodes
nl(Module) -- load module on all nodes
pid(X,Y,Z) -- convert X,Y,Z to a Pid
pwd()      -- print working directory
q()        -- quit - shorthand for init:stop()
regs()     -- information about registered processes
nregs()    -- information about all registered processes
xm(M)      -- cross reference check a module
y(File)    -- generate a Yecc parser
** commands in module i (interpreter interface) **
ih()       -- print help for the i module
true
2> 

sublime text %% 简单，方便，强大
vim          %% 强大，难学习
emacs        %% 强大，难学习
notepad++    %% 简单，win下可以使用
gedit        %% 简单，