erlang_cheatsheet.adoc

Erlang Cheatsheet

The quirks of exit signals and exception handling you always forget

Trapping Exits

Trapping exits means the exit signals are converted to messages before being sent to the process. Trapping exits is done on a per process basis. Execute process_flag(trap_exit, true). in the process you want to be trapping exits.

Exit Signals

Exit Type	Initiated by	Not trapping exits	Trapping exits
Normal	exit(Pid, normal)	Nothing	Receives {'EXIT', Pid, normal}
Normal	exit(self(), normal)	Terminates normally	Receives {'EXIT', Pid, normal}
Abnormal	exit(Pid, Reason)	Terminates abnormally	Receives {'EXIT', Pid, Reason}
Kill	exit(Pid, kill)	Terminates abnormally	Terminates abnormally

Raising and Handling Exceptions

Purpose	Expression to generate	try catch handling pattern	trap_exit message
Stop execution because of runtime error	exit/2	error:Reason	{'EXIT', Pid, Reason}
Stop execution for any reason	exit/1	exit:Reason	{'EXIT', Pid, Reason}
non-local return	throw/1	throw:Reason	{'EXIT', Pid, {{nocatch, Reason}, MFA}}

Errors

badmatch

pattern match error

badarg

BIF called with the wrong type

badarith

arithmetic error

undef

function not defined

function_clause

no matching function clause

if_clause

no matching if clause

case_clause

no matching case clause

Process Relationships

Name	Type	Purpose	Function to Create / Example Calls	Function to Destroy / Example Calls
Link	Symmetrical	Propagate exit signal from a process to all linked processes	link/1, spawn_link/1,2,3,4 link(Pid).	unlink/1 unlink(Pid)
Monitor	Asymmetrical	Sends a message to the monitoring process when the monitored process dies	monitor/2, spawn_monitor/1,3 monitor(Pid)	demonitor/1,2 demonitor(Pid)

Created by Stratus3D  Copyright 2018.  Source Code