Introducing Erlang

Appendix A. An Erlang Parts Catalog

Like every language, Erlang has drawers full of parts that are fun to peruse. These are a very few of the more common ones. If you want much much more, see http://www.erlang.org/doc/reference_manual/users_guide.html.

Shell Commands

You can use most Erlang functions from the shell, but these are ones that are exclusive to the shell.

Table A-1. Erlang shell commands

Command	Action
q()	Quits the shell and the Erlang runtime.
c(file)	Compiles the specified Erlang file.
b()	Displays all variable bindings.
f()	Clears all variable bindings.
f(X)	Clears specified variable binding.
h()	Prints the history list of commands.
e(N)	Repeats the command on line N.
v(N)	The return value of line N.
catch_exception(boolean)	Sets how strict the shell will be in passing errors.
rd(Name,Definition)	Defines a record type Name with contents specified by Definition.
rr(File)	Defines record types based on the contents of File.
rf()	Clears all record definitions. Can also clear specific definitions.
rl()	Lists all current record definitions.
pwd()	Gets the present working directory.
ls()	Lists files at the current location.
cd(Directory)	Changes to the specified Directory.

Reserved Words

There are a few Erlang terms you can’t use outside of their intended context.

The Erlang compiler will wonder what you’re trying to do if you use certain keywords as atoms or function names. It will try to treat your atoms as if they were code, and you can get very strange errors. After all, you should be able to have something ...