Types:

Returns an integer or float that is the arithmetical absolute value of Float or Int, for example:

> abs(-3.33).
3.33
> abs(-3).
3

Allowed in guard tests.

Types:

Computes and returns the adler32 checksum for Data.

Types:

Continues computing the adler32 checksum by combining the previous checksum, OldAdler, with the checksum of Data.

The following code:

X = erlang:adler32(Data1),
Y = erlang:adler32(X,Data2).

assigns the same value to Y as this:

Y = erlang:adler32([Data1,Data2]).

Types:

Combines two previously computed adler32 checksums. This computation requires the size of the data object for the second checksum to be known.

The following code:

Y = erlang:adler32(Data1),
Z = erlang:adler32(Y,Data2).

assigns the same value to Z as this:

X = erlang:adler32(Data1),
Y = erlang:adler32(Data2),
Z = erlang:adler32_combine(X,Y,iolist_size(Data2)).

Types:

Create an alias which can be used when sending messages to the process that created the alias. When the alias has been deactivated, messages sent using the alias will be dropped. An alias can be deactivated using unalias/1. Currently available options for alias/1:

Example:

server() ->


    receive


        {request, AliasReqId, Request} ->


            Result = perform_request(Request),


            AliasReqId ! {reply, AliasReqId, Result}


    end,


    server().
client(ServerPid, Request) ->


    AliasReqId = alias([reply]),


    ServerPid ! {request, AliasReqId, Request},


    %% Alias will be automatically deactivated if we receive a reply


    %% since we used the 'reply' option...


    receive


        {reply, AliasReqId, Result} -> Result


    after 5000 ->


            unalias(AliasReqId),


            %% Flush message queue in case the reply arrived


            %% just before the alias was deactivated...


            receive {reply, AliasReqId, Result} -> Result


            after 0 -> exit(timeout)


            end


    end.
	

Note that both the server and the client in this example must be executing on at least OTP 24 systems in order for this to work.

For more information on process aliases see the Process Aliases section of the Erlang Reference Manual .

Types:

Returns a new tuple that has one element more than Tuple1, and contains the elements in Tuple1 followed by Term as the last element. Semantically equivalent to list_to_tuple(tuple_to_list(Tuple1) ++ [Term]), but much faster. Example:

> erlang:append_element({one, two}, three).
{one,two,three}

Types:

Calls a fun, passing the elements in Args as arguments.

If the number of elements in the arguments are known at compile time, the call is better written as Fun(Arg1, Arg2, ... ArgN).

Types:

Returns the result of applying Function in Module to Args. The applied function must be exported from Module. The arity of the function is the length of Args. Example:

> apply(lists, reverse, [[a, b, c]]).
[c,b,a]
> apply(erlang, atom_to_list, ['Erlang']).
"Erlang"

If the number of arguments are known at compile time, the call is better written as Module:Function(Arg1, Arg2, ..., ArgN).

Failure: error_handler:undefined_function/3 is called if the applied function is not exported. The error handler can be redefined (see process_flag/2). If error_handler is undefined, or if the user has redefined the default error_handler so the replacement module is undefined, an error with reason undef is generated.

Types:

The same as atom_to_binary(Atom, utf8).

Types:

Returns a binary corresponding to the text representation of Atom. If Encoding is latin1, one byte exists for each character in the text representation. If Encoding is utf8 or unicode, the characters are encoded using UTF-8 where characters may require multiple bytes.

Example:

> atom_to_binary('Erlang', latin1).
<<"Erlang">>

Types:

Returns a list of unicode code points corresponding to the text representation of Atom, for example:

> atom_to_list('Erlang').
"Erlang"

> atom_to_list('你好').
[20320,22909]

See unicode(3erl) for how to convert the resulting list to different formats.

Types:

Extracts the part of the binary described by PosLen.

Negative length can be used to extract bytes at the end of a binary, for example:

1> Bin = <<1,2,3,4,5,6,7,8,9,10>>.
2> binary_part(Bin,{byte_size(Bin), -5}).
<<6,7,8,9,10>>

Failure: badarg if PosLen in any way references outside the binary.

Start is zero-based, that is:

1> Bin = <<1,2,3>>
2> binary_part(Bin,{0,2}).
<<1,2>>

For details about the PosLen semantics, see binary(3erl).

Allowed in guard tests.

Types:

The same as binary_part(Subject, {Start, Length}).

Allowed in guard tests.

Types:

The same as binary_to_atom(Binary, utf8).

Types:

Returns the atom whose text representation is Binary. If Encoding is utf8 or unicode, the binary must contain valid UTF-8 sequences.

Examples:

> binary_to_atom(<<"Erlang">>, latin1).
'Erlang'

> binary_to_atom(<<1024/utf8>>, utf8).

Types:

The same as binary_to_existing_atom (Binary, utf8).

Types:

As binary_to_atom/2, but the atom must exist.

The Erlang system has a configurable limit for the total number of atoms that can exist, and atoms are not garbage collected. Therefore, it is not safe to create many atoms from binaries that come from an untrusted source (for example, a file fetched from the Internet), for example, using binary_to_atom/2. This function is thus the appropriate option when the input binary comes from an untrusted source.

An atom exists in an Erlang system when included in a loaded Erlang module or when created programmatically (for example, by binary_to_atom/2). See the next note for an example of when an atom exists in the source code for an Erlang module but not in the compiled version of the same module.

Failure: badarg if the atom does not exist.

Types:

Returns the float whose text representation is Binary, for example:

> binary_to_float(<<"2.2017764e+0">>).
2.2017764

The float string format is the same as the format for Erlang float literals except for that underscores are not permitted.

Failure: badarg if Binary contains a bad representation of a float.

Types:

Returns an integer whose text representation is Binary, for example:

> binary_to_integer(<<"123">>).
123

binary_to_integer/1 accepts the same string formats as list_to_integer/1.

Failure: badarg if Binary contains a bad representation of an integer.

Types:

Returns an integer whose text representation in base Base is Binary, for example:

> binary_to_integer(<<"3FF">>, 16).
1023

binary_to_integer/2 accepts the same string formats as list_to_integer/2.

Failure: badarg if Binary contains a bad representation of an integer.

Types:

Returns a list of integers corresponding to the bytes of Binary.

Types:

As binary_to_list/1, but returns a list of integers corresponding to the bytes from position Start to position Stop in Binary. The positions in the binary are numbered starting from 1.

Types:

Returns an Erlang term that is the result of decoding binary object Binary, which must be encoded according to the Erlang external term format.

> Bin = term_to_binary(hello).
<<131,100,0,5,104,101,108,108,111>>
> hello = binary_to_term(Bin).
hello

See also term_to_binary/1 and binary_to_term/2.

Types:

As binary_to_term/1, but takes these options:

> binary_to_term(<<131,100,0,5,"hello">>, [safe]).
** exception error: bad argument
> hello.
hello
> binary_to_term(<<131,100,0,5,"hello">>, [safe]).
hello

> Input = <<131,100,0,5,"hello","world">>.
<<131,100,0,5,104,101,108,108,111,119,111,114,108,100>>
> {Term, Used} = binary_to_term(Input, [used]).
{hello, 9}
> split_binary(Input, Used).
{<<131,100,0,5,104,101,108,108,111>>, <<"world">>}

Failure: badarg if safe is specified and unsafe data is decoded.

See also term_to_binary/1, binary_to_term/1, and list_to_existing_atom/1.

Types:

Returns an integer that is the size in bits of Bitstring, for example:

> bit_size(<<433:16,3:3>>).
19
> bit_size(<<1,2,3>>).
24

Allowed in guard tests.

Types:

Returns a list of integers corresponding to the bytes of Bitstring. If the number of bits in the binary is not divisible by 8, the last element of the list is a bitstring containing the remaining 1-7 bits. Examples:

> bitstring_to_list(<<433:16>>).
[1,177]

> bitstring_to_list(<<433:16,3:3>>).
[1,177,<<3:3>>]

Types:

This implementation-dependent function increments the reduction counter for the calling process. In the Beam emulator, the reduction counter is normally incremented by one for each function and BIF call. A context switch is forced when the counter reaches the maximum number of reductions for a process (4000 reductions in Erlang/OTP 19.2 and later).

Types:

Returns an integer that is the number of bytes needed to contain Bitstring. That is, if the number of bits in Bitstring is not divisible by 8, the resulting number of bytes is rounded up. Examples:

> byte_size(<<433:16,3:3>>).
3
> byte_size(<<1,2,3>>).
3

Allowed in guard tests.

Types:

Cancels a timer. The same as calling erlang:cancel_timer(TimerRef, []).

Types:

Cancels a timer that has been created by erlang:start_timer or erlang:send_after. TimerRef identifies the timer, and was returned by the BIF that created the timer.

Options:

More Options may be added in the future.

If Result is an integer, it represents the time in milliseconds left until the canceled timer would have expired.

If Result is false, a timer corresponding to TimerRef could not be found. This can be either because the timer had expired, already had been canceled, or because TimerRef never corresponded to a timer. Even if the timer had expired, it does not tell you if the time-out message has arrived at its destination yet.

See also erlang:send_after/4, erlang:start_timer/4, and erlang:read_timer/2.

Types:

Returns the smallest integer not less than Number. For example:

> ceil(5.5).
6

Allowed in guard tests.

Types:

Returns true if Module has old code, otherwise false.

See also code(3erl).

Types:

The same as check_process_code(Pid, Module, []).

Types:

Checks if the node local process identified by Pid executes old code for Module.

Options:

If Pid equals self(), and no async option has been passed, the operation is performed at once. Otherwise a request for the operation is sent to the process identified by Pid, and is handled when appropriate. If no async option has been passed, the caller blocks until CheckResult is available and can be returned.

CheckResult informs about the result of the request as follows:

As of ERTS version 9.0, the check process code operation only checks for direct references to the code. Indirect references via funs will be ignored. If such funs exist and are used after a purge of the old code, an exception will be raised upon usage (same as the case when the fun is received by the process after the purge). Literals will be taken care of (copied) at a later stage. This behavior can as of ERTS version 8.1 be enabled when building OTP, and will automatically be enabled if dirty scheduler support is enabled.

See also code(3erl).

Failures:

Types:

Converts the Time value of time unit FromUnit to the corresponding ConvertedTime value of time unit ToUnit. The result is rounded using the floor function.

Types:

Computes and returns the crc32 (IEEE 802.3 style) checksum for Data.

Types:

Continues computing the crc32 checksum by combining the previous checksum, OldCrc, with the checksum of Data.

The following code:

X = erlang:crc32(Data1),
Y = erlang:crc32(X,Data2).

assigns the same value to Y as this:

Y = erlang:crc32([Data1,Data2]).

Types:

Combines two previously computed crc32 checksums. This computation requires the size of the data object for the second checksum to be known.

The following code:

Y = erlang:crc32(Data1),
Z = erlang:crc32(Y,Data2).

assigns the same value to Z as this:

X = erlang:crc32(Data1),
Y = erlang:crc32(Data2),
Z = erlang:crc32_combine(X,Y,iolist_size(Data2)).

Types:

Returns the current date as {Year, Month, Day}.

The time zone and Daylight Saving Time correction depend on the underlying OS. The return value is based on the OS System Time. Example:

> date().
{1995,2,19}

Types:

Decodes the binary Bin according to the packet protocol specified by Type. Similar to the packet handling done by sockets with option {packet,Type}.

If an entire packet is contained in Bin, it is returned together with the remainder of the binary as {ok,Packet,Rest}.

If Bin does not contain the entire packet, {more,Length} is returned. Length is either the expected total size of the packet, or undefined if the expected packet size is unknown. decode_packet can then be called again with more data added.

If the packet does not conform to the protocol format, {error,Reason} is returned.

Types:

Options:

Examples:

> erlang:decode_packet(1,<<3,"abcd">>,[]).
{ok,<<"abc">>,<<"d">>}
> erlang:decode_packet(1,<<5,"abcd">>,[]).
{more,6}

Types:

Returns a new tuple with element at Index removed from tuple Tuple1, for example:

> erlang:delete_element(2, {one, two, three}).
{one,three}

Types:

Makes the current code for Module become old code and deletes all references for this module from the export table. Returns undefined if the module does not exist, otherwise true.

Failure: badarg if there already is an old version of Module.

Types:

If MonitorRef is a reference that the calling process obtained by calling monitor/2, this monitoring is turned off. If the monitoring is already turned off, nothing happens.

Once demonitor(MonitorRef) has returned, it is guaranteed that no {'DOWN', MonitorRef, _, _, _} message, because of the monitor, will be placed in the caller message queue in the future. However, a {'DOWN', MonitorRef, _, _, _} message can have been placed in the caller message queue before the call. It is therefore usually advisable to remove such a 'DOWN' message from the message queue after monitoring has been stopped. demonitor(MonitorRef, [flush]) can be used instead of demonitor(MonitorRef) if this cleanup is wanted.

The current behavior can be viewed as two combined operations: asynchronously send a "demonitor signal" to the monitored entity and ignore any future results of the monitor.

Failure: It is an error if MonitorRef refers to a monitoring started by another process. Not all such cases are cheap to check. If checking is cheap, the call fails with badarg, for example if MonitorRef is a remote reference.

Types:

The returned value is true unless info is part of OptionList.

demonitor(MonitorRef, []) is equivalent to demonitor(MonitorRef).

Options:

demonitor(MonitorRef),
receive


    {_, MonitorRef, _, _, _} ->


        true
after 0 ->


        true
end

Failures:

Types:

Forces the disconnection of a node. This appears to the node Node as if the local node has crashed. This BIF is mainly used in the Erlang network authentication protocols.

Returns true if disconnection succeeds, otherwise false. If the local node is not alive, ignored is returned.

Types:

Prints a text representation of Term on the standard output.

Types:

Get distribution channel data from the local node that is to be passed to the remote node. The distribution channel is identified by DHandle. If no data is available, the atom none is returned. One can request to be informed by a message when more data is available by calling erlang:dist_ctrl_get_data_notification(DHandle).

The returned value when there are data available depends on the value of the get_size option configured on the distribution channel identified by DHandle. For more information see the documentation of the get_size option for the erlang:dist_ctrl_set_opt/3 function.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Returns the value of the get_size option on the distribution channel identified by DHandle. For more information see the documentation of the get_size option for the erlang:dist_ctrl_set_opt/3 function.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Request notification when more data is available to fetch using erlang:dist_ctrl_get_data(DHandle) for the distribution channel identified by DHandle. When more data is present, the caller will be sent the message dist_data. Once a dist_data messages has been sent, no more dist_data messages will be sent until the dist_ctrl_get_data_notification/1 function has been called again.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Register an alternate input handler process for the distribution channel identified by DHandle. Once this function has been called, InputHandler is the only process allowed to call erlang:dist_ctrl_put_data(DHandle, Data) with the DHandle identifying this distribution channel.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Deliver distribution channel data from a remote node to the local node.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Sets the value of the get_size option on the distribution channel identified by DHandle. This option controls the return value of calls to erlang:dist_ctrl_get_data(DHandle) where DHandle equals DHandle used when setting this option. When the get_size option is:

All options are set to default when a channel is closed.

This function is used when implementing an alternative distribution carrier using processes as distribution controllers. DHandle is retrieved via the callback f_handshake_complete. More information can be found in the documentation of ERTS User's Guide ➜ How to implement an Alternative Carrier for the Erlang Distribution ➜ Distribution Module.

Types:

Returns the Nth element (numbering from 1) of Tuple, for example:

> element(2, {a, b, c}).
b

Allowed in guard tests.

Types:

Returns the process dictionary and deletes it, for example:

> put(key1, {1, 2, 3}),
put(key2, [a, b, c]),
erase().
[{key1,{1,2,3}},{key2,[a,b,c]}]

Types:

Returns the value Val associated with Key and deletes it from the process dictionary. Returns undefined if no value is associated with Key. The average time complexity for the current implementation of this function is O(1) and the worst case time complexity is O(N), where N is the number of items in the process dictionary. Example:

> put(key1, {merry, lambs, are, playing}),
X = erase(key1),
{X, erase(key1)}.
{{merry,lambs,are,playing},undefined}

Types:

Raises an exception of class error with the reason Reason. As evaluating this function causes an exception to be thrown, it has no return value.

The intent of the exception class error is to signal that an unexpected error has happened (for example, a function is called with a parameter that has an incorrect type). See the guide about errors and error handling for additional information. Example:

> catch error(foobar).
{'EXIT',{foobar,[{shell,apply_fun,3,


                        [{file,"shell.erl"},{line,906}]},


                 {erl_eval,do_apply,6,[{file,"erl_eval.erl"},{line,677}]},


                 {erl_eval,expr,5,[{file,"erl_eval.erl"},{line,430}]},


                 {shell,exprs,7,[{file,"shell.erl"},{line,687}]},


                 {shell,eval_exprs,7,[{file,"shell.erl"},{line,642}]},


                 {shell,eval_loop,3,[{file,"shell.erl"},{line,627}]}]}}

Types:

Raises an exception of class error with the reason Reason. Args is expected to be the list of arguments for the current function or the atom none. If it is a list, it is used to provide the arguments for the current function in the stack back-trace. If it is none, the arity of the calling function is used in the stacktrace. As evaluating this function causes an exception to be raised, it has no return value.

The intent of the exception class error is to signal that an unexpected error has happened (for example, a function is called with a parameter that has an incorrect type). See the guide about errors and error handling for additional information. Example:

test.erl:

-module(test).
-export([example_fun/2]).
example_fun(A1, A2) ->


    erlang:error(my_error, [A1, A2]).

Erlang shell:

6> c(test).
{ok,test}
7> test:example_fun(arg1,"this is the second argument").
** exception error: my_error


     in function  test:example_fun/2


         called as test:example_fun(arg1,"this is the second argument")


 

Types:

Raises an exception of class error with the reason Reason. Args is expected to be the list of arguments for the current function or the atom none. If it is a list, it is used to provide the arguments for the current function in the stack back-trace. If it is none, the arity of the calling function is used in the stacktrace. As evaluating this function causes an exception to be raised, it has no return value.

If the error_info option is given, the ErrorInfoMap will be inserted into the stacktrace. The information given in the ErrorInfoMap is to be used by error formatters such as erl_error to provide more context around an error.

The default module of the ErrorInfoMap is the module that the call to error/3 is made. The default function is format_error. See format_error/2 for more details on how this Module:Function/2 is to be used

The intent of the exception class error is to signal that an unexpected error has happened (for example, a function is called with a parameter that has an incorrect type). See the guide about errors and error handling for additional information.

Types:

Raises an exception of class exit with exit reason Reason. As evaluating this function causes an exception to be raised, it has no return value.

The intent of the exception class exit is that the current process should be stopped (for example when a message telling a process to stop is received).

This function differ from error/1,2,3 by causing an exception of a different class and by having a reason that does not include the list of functions from the call stack.

See the guide about errors and error handling for additional information.

Example:

> exit(foobar).
** exception exit: foobar
> catch exit(foobar).
{'EXIT',foobar}

Types:

Sends an exit signal with exit reason Reason to the process or port identified by Pid.

The following behavior applies if Reason is any term, except normal or kill, and P is the process or port identified by Pid:

The following behavior applies if Reason is the term normal and Pid is the identifier of a process P which is not the same as the process that invoked erlang:exit(Pid, normal) (the behavior when a process sends a signal with the normal reason to itself is described in the warning):

If Reason is the atom kill, that is, if exit(Pid, kill) is called, an untrappable exit signal is sent to the process that is identified by Pid, which unconditionally exits with exit reason killed. The exit reason is changed from kill to killed to hint to linked processes that the killed process got killed by a call to exit(Pid, kill).

Note that the behavior described above is different from when a process sends an exit signal with reason normal to another process. This is arguably strange but this behavior is kept for backward compatibility reasons.

Types:

Calculates, without doing the encoding, the maximum byte size for a term encoded in the Erlang external term format. The following condition applies always:

> Size1 = byte_size(term_to_binary(Term)),
> Size2 = erlang:external_size(Term),
> true = Size1 =< Size2.
true

This is equivalent to a call to:

erlang:external_size(Term, [])

Types:

Calculates, without doing the encoding, the maximum byte size for a term encoded in the Erlang external term format. The following condition applies always:

> Size1 = byte_size(term_to_binary(Term, Options)),
> Size2 = erlang:external_size(Term, Options),
> true = Size1 =< Size2.
true

Option {minor_version, Version} specifies how floats are encoded. For a detailed description, see term_to_binary/2.

Types:

Returns a float by converting Number to a float, for example:

> float(55).
55.0

Allowed in guard tests.

When float/1 is used in an expression in a guard, such as 'float(A) == 4.0', it converts a number as described earlier.

Types:

The same as float_to_binary(Float,[{scientific,20}]).

Types:

Returns a binary corresponding to the text representation of Float using fixed decimal point formatting. Options behaves in the same way as float_to_list/2. Examples:

> float_to_binary(7.12, [{decimals, 4}]).
<<"7.1200">>
> float_to_binary(7.12, [{decimals, 4}, compact]).
<<"7.12">>
> float_to_binary(7.12, [{scientific, 3}]).
<<"7.120e+00">>
> float_to_binary(7.12, [short]).
<<"7.12">>
> float_to_binary(0.1+0.2, [short]).
<<"0.30000000000000004">>
> float_to_binary(0.1+0.2)
<<"3.00000000000000044409e-01">>

Types:

The same as float_to_list(Float,[{scientific,20}]).

Types:

Returns a string corresponding to the text representation of Float using fixed decimal point formatting.

Available options:

Examples:

> float_to_list(7.12, [{decimals, 4}]).
"7.1200"
> float_to_list(7.12, [{decimals, 4}, compact]).
"7.12"
> float_to_list(7.12, [{scientific, 3}]).
"7.120e+00"
> float_to_list(7.12, [short]).
"7.12"
> float_to_list(0.1+0.2, [short]).
"0.30000000000000004"
> float_to_list(0.1+0.2)
"3.00000000000000044409e-01"

In the last example, float_to_list(0.1+0.2) evaluates to "3.00000000000000044409e-01". The reason for this is explained in Representation of Floating Point Numbers.

Types:

Returns the largest integer not greater than Number. For example:

> floor(-10.5).
-11

Allowed in guard tests.

Types:

Returns a list with information about the fun Fun. Each list element is a tuple. The order of the tuples is undefined, and more tuples can be added in a future release.

Two types of funs have slightly different semantics:

The following elements are always present in the list for both local and external funs:

The following elements are only present in the list if Fun is local:

Types:

fun_info_item() = 


    arity | env | index | name | module | new_index | new_uniq |


    pid | type | uniq

Returns information about Fun as specified by Item, in the form {Item,Info}.

For any fun, Item can be any of the atoms module, name, arity, env, or type.

For a local fun, Item can also be any of the atoms index, new_index, new_uniq, uniq, and pid. For an external fun, the value of any of these items is always the atom undefined.

See erlang:fun_info/1.

Types:

Returns String that represents the code that created Fun.

String has the following form, if Fun was created by a fun expression of the form fun ModuleName:FuncName/Arity:

"fun ModuleName:FuncName/Arity"

The form of String when Fun is created from other types of fun expressions differs depending on if the fun expression was executed while executing compiled code or if the fun expression was executed while executing uncompiled code (uncompiled escripts, the Erlang shell, and other code executed by the erl_eval module):

Examples:

-module(test).
-export([add/1, add2/0, fun_tuple/0]).
add(A) -> fun(B) -> A + B end.
add2() -> fun add/1.
fun_tuple() -> {fun() -> 1 end, fun() -> 1 end}.


        

> {fun test:add/1, test:add2()}.
{fun test:add/1,#Fun<test.1.107738983>}

Explanation: fun test:add/1 is upgradable but test:add2() is not upgradable.

> {test:add(1), test:add(42)}.
{#Fun<test.0.107738983>,#Fun<test.0.107738983>}

Explanation: test:add(1) and test:add(42) has the same string representation as the environment is not taken into account.

>test:fun_tuple().
{#Fun<test.2.107738983>,#Fun<test.3.107738983>}

Explanation: The string representations differ because the funs come from different fun expressions.

> {fun() -> 1 end, fun() -> 1 end}. > 
{#Fun<erl_eval.45.97283095>,#Fun<erl_eval.45.97283095>}

Explanation: All funs created from fun expressions of this form in uncompiled code with the same arity are mapped to the same list by fun_to_list/1.

Types:

Returns true if the module Module is current and contains an exported function Function/Arity, or if there is a BIF (a built-in function implemented in C) with the specified name, otherwise returns false.

Forces an immediate garbage collection of the executing process. The function is not to be used unless it has been noticed (or there are good reasons to suspect) that the spontaneous garbage collection will occur too late or not at all.

Types:

The same as garbage_collect(Pid, []).

Types:

Garbage collects the node local process identified by Pid.

Option:

If Pid equals self(), and no async option has been passed, the garbage collection is performed at once, that is, the same as calling garbage_collect/0. Otherwise a request for garbage collection is sent to the process identified by Pid, and will be handled when appropriate. If no async option has been passed, the caller blocks until GCResult is available and can be returned.

GCResult informs about the result of the garbage collection request as follows:

Notice that the same caveats apply as for garbage_collect/0.

Failures:

Types:

Returns the process dictionary as a list of {Key, Val} tuples. The items in the returned list can be in any order. Example:

> put(key1, merry),
put(key2, lambs),
put(key3, {are, playing}),
get().
[{key1,merry},{key2,lambs},{key3,{are,playing}}]

Types:

Returns the value Val associated with Key in the process dictionary, or undefined if Key does not exist. The expected time complexity for the current implementation of this function is O(1) and the worst case time complexity is O(N), where N is the number of items in the process dictionary. Example:

> put(key1, merry),
put(key2, lambs),
put({any, [valid, term]}, {are, playing}),
get({any, [valid, term]}).
{are,playing}

Types:

Returns the magic cookie of the local node if the node is alive, otherwise the atom nocookie. This value is set by set_cookie/1.

Types:

Returns the magic cookie for node Node if the local node is alive, otherwise the atom nocookie. This value is set by set_cookie/2.

Types:

Returns a list of all keys present in the process dictionary. The items in the returned list can be in any order. Example:

> put(dog, {animal,1}),
put(cow, {animal,2}),
put(lamb, {animal,3}),
get_keys().
[dog,cow,lamb]

Types:

Returns a list of keys that are associated with the value Val in the process dictionary. The items in the returned list can be in any order. Example:

> put(mary, {1, 2}),
put(had, {1, 2}),
put(a, {1, 2}),
put(little, {1, 2}),
put(dog, {1, 3}),
put(lamb, {1, 2}),
get_keys({1, 2}).
[mary,had,a,little,lamb]

Returns the process identifier of the group leader for the process evaluating the function.

Every process is a member of some process group and all groups have a group leader. All I/O from the group is channeled to the group leader. When a new process is spawned, it gets the same group leader as the spawning process. Initially, at system startup, init is both its own group leader and the group leader of all processes.

Types:

Sets the group leader of Pid to GroupLeader. Typically, this is used when a process started from a certain shell is to have another group leader than init.

The group leader should be rarely changed in applications with a supervision tree, because OTP assumes the group leader of their processes is their application master.

Setting the group leader follows the signal ordering guarantees described in the Processes Chapter in the Erlang Reference Manual .

See also group_leader/0 and OTP design principles related to starting and stopping applications.

The same as halt(0, []). Example:

> halt().
os_prompt%

Types:

The same as halt(Status, []). Example:

> halt(17).
os_prompt% echo $?
17
os_prompt%

Types:

Status must be a non-negative integer, a string, or the atom abort. Halts the Erlang runtime system. Has no return value. Depending on Status, the following occurs:

For integer Status, the Erlang runtime system closes all ports and allows async threads to finish their operations before exiting. To exit without such flushing, use Option as {flush,false}.

For statuses string() and abort, option flush is ignored and flushing is not done.

Types:

Returns the head of List, that is, the first element, for example:

> hd([1,2,3,4,5]).
1

Allowed in guard tests.

Failure: badarg if List is the empty list [].

Types:

Puts the calling process into a wait state where its memory allocation has been reduced as much as possible. This is useful if the process does not expect to receive any messages soon.

The process is awaken when a message is sent to it, and control resumes in Module:Function with the arguments specified by Args with the call stack emptied, meaning that the process terminates when that function returns. Thus erlang:hibernate/3 never returns to its caller. The resume function Module:Function/Arity must be exported (Arity =:= length(Args)).

If the process has any message in its message queue, the process is awakened immediately in the same way as described earlier.

In more technical terms, erlang:hibernate/3 discards the call stack for the process, and then garbage collects the process. After this, all live data is in one continuous heap. The heap is then shrunken to the exact same size as the live data that it holds (even if that size is less than the minimum heap size for the process).

If the size of the live data in the process is less than the minimum heap size, the first garbage collection occurring after the process is awakened ensures that the heap size is changed to a size not smaller than the minimum heap size.

Notice that emptying the call stack means that any surrounding catch is removed and must be re-inserted after hibernation. One effect of this is that processes started using proc_lib (also indirectly, such as gen_server processes), are to use proc_lib:hibernate/3 instead, to ensure that the exception handler continues to work when the process wakes up.

Types:

Returns a new tuple with element Term inserted at position Index in tuple Tuple1. All elements from position Index and upwards are pushed one step higher in the new tuple Tuple2. Example:

> erlang:insert_element(2, {one, two, three}, new).
{one,new,two,three}

Types:

Returns a binary corresponding to the text representation of Integer, for example:

> integer_to_binary(77).
<<"77">>

Types:

Returns a binary corresponding to the text representation of Integer in base Base, for example:

> integer_to_binary(1023, 16).
<<"3FF">>

Types:

Returns a string corresponding to the text representation of Integer, for example:

> integer_to_list(77).
"77"

Types:

Returns a string corresponding to the text representation of Integer in base Base, for example:

> integer_to_list(1023, 16).
"3FF"

Types:

Returns an integer, that is the size in bytes, of the binary that would be the result of iolist_to_binary(Item), for example:

> iolist_size([1,2|<<3,4>>]).
4

Types:

Returns a binary that is made from the integers and binaries in IoListOrBinary, for example:

> Bin1 = <<1,2,3>>.
<<1,2,3>>
> Bin2 = <<4,5>>.
<<4,5>>
> Bin3 = <<6>>.
<<6>>
> iolist_to_binary([Bin1,1,[2,3,Bin2],4|Bin3]).
<<1,2,3,1,2,3,4,5,4,6>>

Types:

Returns an iovec that is made from the integers and binaries in IoListOrBinary. This function is useful when you want to flatten an iolist but you do not need a single binary. This can be useful for passing the data to nif functions such as enif_inspect_iovec or do more efficient message passing. The advantage of using this function over iolist_to_binary/1 is that it does not have to copy off-heap binaries. Example:

> Bin1 = <<1,2,3>>.
<<1,2,3>>
> Bin2 = <<4,5>>.
<<4,5>>
> Bin3 = <<6>>.
<<6>>
%% If you pass small binaries and integers it works as iolist_to_binary
> erlang:iolist_to_iovec([Bin1,1,[2,3,Bin2],4|Bin3]).
[<<1,2,3,1,2,3,4,5,4,6>>]
%% If you pass larger binaries, they are split and returned in a form
%% optimized for calling the C function writev.
> erlang:iolist_to_iovec([<<1>>,<<2:8096>>,<<3:8096>>]).
[<<1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,


   0,...>>,


 <<0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,


   ...>>,


 <<0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...>>]

Returns true if the local node is alive (that is, if the node can be part of a distributed system), otherwise false. A node is alive if it is started with:

A node can also be alive if it has got a name from a call to net_kernel:start/1 and has not been stopped by a call to net_kernel:stop/0.

Types:

Returns true if Term is an atom, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a binary, otherwise false.

A binary always contains a complete number of bytes.

Allowed in guard tests.

Types:

Returns true if Term is a bitstring (including a binary), otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is the atom true or the atom false (that is, a boolean). Otherwise returns false.

Allowed in guard tests.

Types:

This BIF is useful for builders of cross-reference tools.

Returns true if Module:Function/Arity is a BIF implemented in C, otherwise false.

Types:

Returns true if Term is a floating point number, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a fun, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a fun that can be applied with Arity number of arguments, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is an integer, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a list with zero or more elements, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a map, otherwise false.

Allowed in guard tests.

Types:

Returns true if map Map contains Key and returns false if it does not contain the Key.

The call fails with a {badmap,Map} exception if Map is not a map.

Example:

> Map = #{"42" => value}.
#{"42" => value}
> is_map_key("42",Map).
true
> is_map_key(value,Map).
false

Allowed in guard tests.

Types:

Returns true if Term is an integer or a floating point number. Otherwise returns false.

Allowed in guard tests.

Types:

Returns true if Term is a process identifier, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a port identifier, otherwise false.

Allowed in guard tests.

Types:

Pid must refer to a process at the local node.

Returns true if the process exists and is alive, that is, is not exiting and has not exited. Otherwise returns false.

If process P1 calls is_process_alive(P2Pid) it is guaranteed that all signals, sent from P1 to P2 (P2 is the process with identifier P2Pid) before the call, will be delivered to P2 before the aliveness of P2 is checked. This guarantee means that one can use is_process_alive/1 to let a process P1 wait until a process P2, which has got an exit signal with reason kill from P1, is killed. Example:

exit(P2Pid, kill),
% P2 might not be killed
is_process_alive(P2Pid),
% P2 is not alive (the call above always return false)

See the documentation about signals and erlang:exit/2 for more information about signals and exit signals.

Types:

Returns true if Term is a tuple and its first element is RecordTag. Otherwise returns false.

Allowed in guard tests, if RecordTag is a literal atom.

Types:

RecordTag must be an atom.

Returns true if Term is a tuple, its first element is RecordTag, and its size is Size. Otherwise returns false.

Allowed in guard tests if RecordTag is a literal atom and Size is a literal integer.

Types:

Returns true if Term is a reference, otherwise false.

Allowed in guard tests.

Types:

Returns true if Term is a tuple, otherwise false.

Allowed in guard tests.

Types:

Returns the length of List, for example:

> length([1,2,3,4,5,6,7,8,9]).
9

Allowed in guard tests.

Types:

Sets up and activates a link between the calling process and another process or a port identified by PidOrPort. We will from here on call the identified process or port linkee. If the linkee is a port, it must reside on the same node as the caller.

If one of the participants of a link terminates, it will send an exit signal to the other participant. The exit signal will contain the exit reason of the terminated participant. Other cases when exit signals are triggered due to a link are when no linkee exist (noproc exit reason) and when the connection between linked processes on different nodes is lost or cannot be established (noconnection exit reason).

An existing link can be removed by calling unlink/1. For more information on links and exit signals due to links, see the Processes chapter in the Erlang Reference Manual :

For historical reasons, link/1 has a strange semi-synchronous behavior when it is "cheap" to check if the linkee exists or not, and the caller does not trap exits. If the above is true and the linkee does not exist, link/1 will raise a noproc error exception. The expected behavior would instead have been that link/1 returned true, and the caller later was sent an exit signal with noproc exit reason, but this is unfortunately not the case. The noproc exception is not to be confused with an exit signal with exit reason noproc. Currently it is "cheap" to check if the linkee exists when it is supposed to reside on the same node as the calling process.

The link setup and activation is performed asynchronously. If the link already exists, or if the caller attempts to create a link to itself, nothing is done. A detailed description of the link protocol can be found in the Distribution Protocol chapter of the ERTS User's Guide .

Failure:

Types:

Returns the atom whose text representation is String.

As from Erlang/OTP 20, String may contain any Unicode character. Earlier versions allowed only ISO-latin-1 characters as the implementation did not allow Unicode characters above 255.

Example:

> list_to_atom("Erlang").
'Erlang'

Types:

Returns a binary that is made from the integers and binaries in IoList, for example:

> Bin1 = <<1,2,3>>.
<<1,2,3>>
> Bin2 = <<4,5>>.
<<4,5>>
> Bin3 = <<6>>.
<<6>>
> list_to_binary([Bin1,1,[2,3,Bin2],4|Bin3]).
<<1,2,3,1,2,3,4,5,4,6>>

Types:

bitstring_list() = 


    maybe_improper_list(byte() | bitstring() | bitstring_list(),


                        bitstring() | [])

Returns a bitstring that is made from the integers and bitstrings in BitstringList. (The last tail in BitstringList is allowed to be a bitstring.) Example:

> Bin1 = <<1,2,3>>.
<<1,2,3>>
> Bin2 = <<4,5>>.
<<4,5>>
> Bin3 = <<6,7:4>>.
<<6,7:4>>
> list_to_bitstring([Bin1,1,[2,3,Bin2],4|Bin3]).
<<1,2,3,1,2,3,4,5,4,6,7:4>>

Types:

Returns the atom whose text representation is String, but only if there already exists such atom. An atom exists if it has been created by the run-time system by either loading code or creating a term in which the atom is part.

Failure: badarg if there does not already exist an atom whose text representation is String.

Types:

Returns the float whose text representation is String, for example:

> list_to_float("2.2017764e+0").
2.2017764

The float string format is the same as the format for Erlang float literals except for that underscores are not permitted.

Failure: badarg if String contains a bad representation of a float.

Types:

Returns an integer whose text representation is String, for example:

> list_to_integer("123").
123

> list_to_integer("-123").
-123

> list_to_integer("+123234982304982309482093833234234").
123234982304982309482093833234234

String must contain at least one digit character and can have an optional prefix consisting of a single "+" or "-" character (that is, String must match the regular expression "^[+-]?[0-9]+$").

Failure: badarg if String contains a bad representation of an integer.

Types:

Returns an integer whose text representation in base Base is String, for example:

> list_to_integer("3FF", 16).
1023

> list_to_integer("+3FF", 16).
1023

> list_to_integer("3ff", 16).
1023

> list_to_integer("3fF", 16).
1023

> list_to_integer("-3FF", 16).
-1023

For example, when Base is 16, String must match the regular expression "^[+-]?([0-9]|[A-F]|[a-f])+$".

Failure: badarg if String contains a bad representation of an integer.

Types:

Returns a process identifier whose text representation is a String, for example:

> list_to_pid("<0.4.1>").
<0.4.1>

Failure: badarg if String contains a bad representation of a process identifier.

Types:

Returns a port identifier whose text representation is a String, for example:

> list_to_port("#Port<0.4>").
#Port<0.4>

Failure: badarg if String contains a bad representation of a port identifier.

Types:

Returns a reference whose text representation is a String, for example:

> list_to_ref("#Ref<0.4192537678.4073193475.71181>").
#Ref<0.4192537678.4073193475.71181>

Failure: badarg if String contains a bad representation of a reference.

Types:

Returns a tuple corresponding to List, for example

> list_to_tuple([share, ['Ericsson_B', 163]]).
{share, ['Ericsson_B', 163]}

List can contain any Erlang terms.

Types:

If Binary contains the object code for module Module, this BIF loads that object code. If the code for module Module already exists, all export references are replaced so they point to the newly loaded code. The previously loaded code is kept in the system as old code, as there can still be processes executing that code.

Returns either {module, Module}, or {error, Reason} if loading fails. Reason is one of the following:

Types:

Loads and links a dynamic library containing native implemented functions (NIFs) for a module. Path is a file path to the shareable object/dynamic library file minus the OS-dependent file extension (.so for Unix and .dll for Windows). Notice that on most OSs the library has to have a different name on disc when an upgrade of the nif is done. If the name is the same, but the contents differ, the old library may be loaded instead. For information on how to implement a NIF library, see erl_nif(3erl).

LoadInfo can be any term. It is passed on to the library as part of the initialization. A good practice is to include a module version number to support future code upgrade scenarios.

The call to load_nif/2 must be made directly from the Erlang code of the module that the NIF library belongs to. It returns either ok, or {error,{Reason,Text}} if loading fails. Reason is one of the following atoms while Text is a human readable string that can give more information about the failure:

If the -nifs() attribute is used (which is recommended), all NIFs in the dynamic library much be declared as such for load_nif/2 to succeed. On the other hand, all functions declared with the -nifs() attribute do not have to be implemented by the dynamic library. This allows a target independent Erlang file to contain fallback implementations for functions that may lack NIF support depending on target OS/hardware platform.

Types:

Returns a list of all loaded Erlang modules (current and old code), including preloaded modules.

See also code(3erl).

Types:

Returns the current local date and time, {{Year, Month, Day}, {Hour, Minute, Second}}, for example:

> erlang:localtime().
{{1996,11,6},{14,45,17}}

The time zone and Daylight Saving Time correction depend on the underlying OS. The return value is based on the OS System Time.

Types:

Converts local date and time to Universal Time Coordinated (UTC), if supported by the underlying OS. Otherwise no conversion is done and Localtime is returned. Example:

> erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}).
{{1996,11,6},{13,45,17}}

Failure: badarg if Localtime denotes an invalid date and time.

Types:

Converts local date and time to Universal Time Coordinated (UTC) as erlang:localtime_to_universaltime/1, but the caller decides if Daylight Saving Time is active.

If IsDst == true, Localtime is during Daylight Saving Time, if IsDst == false it is not. If IsDst == undefined, the underlying OS can guess, which is the same as calling erlang:localtime_to_universaltime(Localtime).

Examples:

> erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, true).
{{1996,11,6},{12,45,17}}
> erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, false).
{{1996,11,6},{13,45,17}}
> erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, undefined).
{{1996,11,6},{13,45,17}}

Failure: badarg if Localtime denotes an invalid date and time.

Returns a unique reference. The reference is unique among connected nodes.

Types:

Creates a new tuple of the specified Arity, where all elements are InitialValue, for example:

> erlang:make_tuple(4, []).
{[],[],[],[]}

Types:

Creates a tuple of size Arity, where each element has value DefaultValue, and then fills in values from InitList. Each list element in InitList must be a two-tuple, where the first element is a position in the newly created tuple and the second element is any term. If a position occurs more than once in the list, the term corresponding to the last occurrence is used. Example:

> erlang:make_tuple(5, [], [{2,ignored},{5,zz},{2,aa}]).
{[],aa,[],[],zz}

Types:

Returns value Value associated with Key if Map contains Key.

The call fails with a {badmap,Map} exception if Map is not a map, or with a {badkey,Key} exception if no value is associated with Key.

Example:

> Key = 1337,


  Map = #{42 => value_two,1337 => "value one","a" => 1},


  map_get(Key,Map).
"value one"

Allowed in guard tests.

Types:

Returns an integer, which is the number of key-value pairs in Map, for example:

> map_size(#{a=>1, b=>2, c=>3}).
3

Allowed in guard tests.

Types:

Tests a match specification used in calls to ets:select/2 and erlang:trace_pattern/3. The function tests both a match specification for "syntactic" correctness and runs the match specification against the object. If the match specification contains errors, the tuple {error, Errors} is returned, where Errors is a list of natural language descriptions of what was wrong with the match specification.

If Type is table, the object to match against is to be a tuple. The function then returns {ok,Result,[],Warnings}, where Result is what would have been the result in a real ets:select/2 call, or false if the match specification does not match the object tuple.

If Type is trace, the object to match against is to be a list. The function returns {ok, Result, Flags, Warnings}, where Result is one of the following:

Flags is a list containing all the trace flags to be enabled, currently this is only return_trace.

This is a useful debugging and test tool, especially when writing complicated match specifications.

See also ets:test_ms/2.

Types:

Returns the largest of Term1 and Term2. If the terms compare equal with the == operator, Term1 is returned.

The Expressions section contains descriptions of the == operator and how terms are ordered.

Examples:

> max(1, 2).
2

> max(1.0, 1).
1.0

> max(1, 1.0).
1

> max("abc", "b").
"b"

Types:

Computes an MD5 message digest from Data, where the length of the digest is 128 bits (16 bytes). Data is a binary or a list of small integers and binaries.

For more information about MD5, see RFC 1321 - The MD5 Message-Digest Algorithm.

Types:

Finishes the update of an MD5 Context and returns the computed MD5 message digest.

Types:

Creates an MD5 context, to be used in the following calls to md5_update/2.

Types:

Update an MD5 Context with Data and returns a NewContext.

Types:

memory_type() = 


    total | processes | processes_used | system | atom |


    atom_used | binary | code | ets

Returns a list with information about memory dynamically allocated by the Erlang emulator. Each list element is a tuple {Type, Size}. The first element Type is an atom describing memory type. The second element Size is the memory size in bytes.

Memory types:

When the emulator is run with instrumentation, the system value is more accurate, but memory directly allocated for malloc (and friends) is still not part of the system value. Direct calls to malloc are only done from OS-specific runtime libraries and perhaps from user-implemented Erlang drivers that do not use the memory allocation functions in the driver interface.

As the total value is the sum of processes and system, the error in system propagates to the total value.

The different amounts of memory that are summed are not gathered atomically, which introduces an error in the result.

The different values have the following relation to each other. Values beginning with an uppercase letter is not part of the result.

total      = processes + system
processes  = processes_used + ProcessesNotUsed
system     = atom + binary + code + ets + OtherSystem
atom       = atom_used + AtomNotUsed
RealTotal  = processes + RealSystem
RealSystem = system + MissedSystem

More tuples in the returned list can be added in a future release.

Also, because of fragmentation and prereservation of memory areas, the size of the memory segments containing the dynamically allocated memory blocks can be much larger than the total size of the dynamically allocated memory blocks.

Failure: notsup if an erts_alloc(3erl) allocator has been disabled.

Types:

memory_type() = 


    total | processes | processes_used | system | atom |


    atom_used | binary | code | ets

Returns the memory size in bytes allocated for memory of type Type. The argument can also be specified as a list of memory_type() atoms, in which case a corresponding list of {memory_type(), Size :: integer >= 0} tuples is returned.

Failures:

See also erlang:memory/0.

Types:

Returns the smallest of Term1 and Term2. If the terms compare equal with the == operator, Term1 is returned.

The Expressions section contains descriptions of the == operator and how terms are ordered.

Examples:

> min(1, 2).
1

> min(1.0, 1).
1.0

> min(1, 1.0).
1

> min("abc", "b").
"abc"

Types:

Returns true if the module Module is loaded as current code ; otherwise, false. It does not attempt to load the module.

Types:

registered_name() = atom()

registered_process_identifier() = 


    registered_name() | {registered_name(), node()}

monitor_process_identifier() = 


    pid() | registered_process_identifier()

monitor_port_identifier() = port() | registered_name()

Sends a monitor request of type Type to the entity identified by Item. If the monitored entity does not exist or it changes monitored state, the caller of monitor/2 is notified by a message on the following format:

{Tag, MonitorRef, Type, Object, Info}

Type can be one of the following atoms: process, port or time_offset.

A process or port monitor is triggered only once, after that it is removed from both monitoring process and the monitored entity. Monitors are fired when the monitored process or port terminates, does not exist at the moment of creation, or if the connection to it is lost. If the connection to it is lost, we do not know if it still exists. The monitoring is also turned off when demonitor/1 is called.

A process or port monitor by name resolves the RegisteredName to pid() or port() only once at the moment of monitor instantiation, later changes to the name registration will not affect the existing monitor.

When a process or port monitor is triggered, a 'DOWN' message is sent that has the following pattern:

{'DOWN', MonitorRef, Type, Object, Info}

In the monitor message MonitorRef and Type are the same as described earlier, and:

{'CHANGE', MonitorRef, Type, Item, NewTimeOffset}

Making several calls to monitor/2 for the same Item and/or Type is not an error; it results in as many independent monitoring instances.

The monitor functionality is expected to be extended. That is, other Types and Items are expected to be supported in a future release.

Types:

registered_name() = atom()

registered_process_identifier() = 


    registered_name() | {registered_name(), node()}

monitor_process_identifier() = 


    pid() | registered_process_identifier()

monitor_port_identifier() = port() | registered_name()

Provides an option list for modification of monitoring functionality provided by monitor/2. The Type and Item arguments have the same meaning as when passed to monitor/2. Currently available options:

server() ->


    receive


        {request, AliasReqId, Request} ->


            Result = perform_request(Request),


            AliasReqId ! {reply, AliasReqId, Result}


    end,


    server().
client(ServerPid, Request) ->


    AliasMonReqId = monitor(process, ServerPid, [{alias, reply_demonitor}]),


    ServerPid ! {request, AliasMonReqId, Request},


    %% Alias as well as monitor will be automatically deactivated if we


    %% receive a reply or a 'DOWN' message since we used 'reply_demonitor'


    %% as unalias option...


    receive


        {reply, AliasMonReqId, Result} ->


            Result;


        {'DOWN', AliasMonReqId, process, ServerPid, ExitReason} ->


            error(ExitReason)


    end.
	    

server() ->


    receive


        {request, From, ReqId, Request} ->


            Result = perform_request(Request),


            From ! {reply, self(), ReqId, Result}


    end,


    server().
client(ServerPids, Request) when is_list(ServerPids) ->


    ReqId = make_ref(),


    lists:foreach(fun (ServerPid) ->


                          _ = monitor(process, ServerPid,


                                      [{tag, {'DOWN', ReqId}}]),


                          ServerPid ! {request, self(), ReqId, Request}


                  end,


                  ServerPids),


    receive_replies(ReqId, length(ServerPids), []).
receive_replies(_ReqId, 0, Acc) ->


    Acc;
receive_replies(ReqId, N, Acc) ->


    %% The compiler will detect that we match on the 'ReqId'


    %% reference in all clauses, and will enable the selective


    %% receive optimization which makes the receive able to


    %% skip past all messages present in the message queue at


    %% the time when the 'ReqId' reference was created...


    Res = receive


              {reply, ServerPid, ReqId, Result} ->


                  %% Here we typically would have deactivated the


                  %% monitor by a call to demonitor(Mon, [flush]) but


                  %% we ignore this in this example for simplicity...


                  {ok, ServerPid, Result};


              {{'DOWN', ReqId}, _Mon, process, ServerPid, ExitReason} ->


                  {error, ServerPid, ExitReason}


          end,


    receive_replies(ReqId, N-1, [Res | Acc]).
	    

Types:

Monitor the status of the node Node. If Flag is true, monitoring is turned on. If Flag is false, monitoring is turned off.

Making several calls to monitor_node(Node, true) for the same Node is not an error; it results in as many independent monitoring instances.

If Node fails or does not exist, the message {nodedown, Node} is delivered to the process. If a process has made two calls to monitor_node(Node, true) and Node terminates, two nodedown messages are delivered to the process. If there is no connection to Node, an attempt is made to create one. If this fails, a nodedown message is delivered.

The delivery of the nodedown signal is not ordered with respect to other link or monitor signals from the node that goes down. If you need a guarantee that all signals from the remote node has been delivered before the nodedown signal is sent, you should use net_kernel:monitor_nodes/1.

Nodes connected through hidden connections can be monitored as any other nodes.

Failure: notalive if the local node is not alive.

Types:

Behaves as monitor_node/2 except that it allows an extra option to be specified, namely allow_passive_connect. This option allows the BIF to wait the normal network connection time-out for the monitored node to connect itself, even if it cannot be actively connected from this node (that is, it is blocked). The state where this can be useful can only be achieved by using the Kernel option dist_auto_connect once. If that option is not used, option allow_passive_connect has no effect.

Failure: badarg if the local node is not alive or the option list is malformed.

Returns the current Erlang monotonic time in native time unit. This is a monotonically increasing time since some unspecified point in time.

Different runtime system instances will use different unspecified points in time as base for their Erlang monotonic clocks. That is, it is pointless comparing monotonic times from different runtime system instances. Different runtime system instances can also place this unspecified point in time different relative runtime system start. It can be placed in the future (time at start is a negative value), the past (time at start is a positive value), or the runtime system start (time at start is zero). The monotonic time at runtime system start can be retrieved by calling erlang:system_info(start_time).

Types:

Returns the current Erlang monotonic time converted into the Unit passed as argument.

Same as calling erlang:convert_time_unit(erlang:monotonic_time(), native, Unit), however optimized for commonly used Units.

Types:

Works exactly like error/1, but Dialyzer thinks that this BIF will return an arbitrary term. When used in a stub function for a NIF to generate an exception when the NIF library is not loaded, Dialyzer does not generate false warnings.

Types:

Works exactly like error/2, but Dialyzer thinks that this BIF will return an arbitrary term. When used in a stub function for a NIF to generate an exception when the NIF library is not loaded, Dialyzer does not generate false warnings.

Types:

Returns the name of the local node. If the node is not alive, nonode@nohost is returned instead.

Allowed in guard tests.

Types:

Returns the node where Arg originates. Arg can be a process identifier, a reference, or a port. If Arg originates from the local node and the local node is not alive, nonode@nohost is returned.

Allowed in guard tests.

Types:

Returns a list of all nodes connected to this node through normal connections (that is, hidden nodes are not listed). Same as nodes(visible).

Types:

Returns a list of nodes according to the argument specified. The returned result, when the argument is a list, is the list of nodes satisfying the disjunction(s) of the list elements.

NodeTypes:

Some equalities: [node()] = nodes(this), nodes(connected) = nodes([visible, hidden]), and nodes() = nodes(visible).

Types:

Returns a list of NodeInfo tuples. The first element is the node name. Nodes to be included in the list are determined by the first argument Arg in the same way as for nodes(Arg). The second element of NodeInfo tuples is a map containing further information about the node identified by the first element. The information present in this map is determined by the InfoOpts map passed as the second argument. Currently the following associations are allowed in the InfoOpts map:

Example:

(a@localhost)1> nodes([this, connected], #{connection_id=>true, node_type=>true}). 
[{c@localhost,#{connection_id => 13892108,node_type => hidden}},


 {b@localhost,#{connection_id => 3067553,node_type => visible}},


 {a@localhost,#{connection_id => undefined,node_type => this}}]
(a@localhost)2> 


        

Types:

timestamp() = 


    {MegaSecs :: integer() >= 0,


     Secs :: integer() >= 0,


     MicroSecs :: integer() >= 0}

For more information, see section Time and Time Correction in the User's Guide. Specifically, section Dos and Dont's describes what to use instead of erlang:now/0.

Returns the tuple {MegaSecs, Secs, MicroSecs}, which is the elapsed time since 00:00 GMT, January 1, 1970 (zero hour), if provided by the underlying OS. Otherwise some other point in time is chosen. It is also guaranteed that the following calls to this BIF return continuously increasing values. Hence, the return value from erlang:now/0 can be used to generate unique time stamps. If it is called in a tight loop on a fast machine, the time of the node can become skewed.

Can only be used to check the local time of day if the time-zone information of the underlying OS is properly configured.

Types:

Returns a port identifier as the result of opening a new Erlang port. A port can be seen as an external Erlang process.

The name of the executable as well as the arguments specified in cd, env, args, and arg0 are subject to Unicode filename translation if the system is running in Unicode filename mode. To avoid translation or to force, for example UTF-8, supply the executable and/or arguments as a binary in the correct encoding. For details, see the module file(3erl), the function file:native_name_encoding/0 in Kernel, and the Using Unicode in Erlang User's Guide.

PortNames:

PortSettings is a list of settings for the port. The valid settings are as follows:

Default is stream for all port types and use_stdio for spawned ports.

Failure: if the port cannot be opened, the exit reason is badarg, system_limit, or the POSIX error code that most closely describes the error, or einval if no POSIX code is appropriate:

During use of a port opened using {spawn, Name}, {spawn_driver, Name}, or {spawn_executable, Name}, errors arising when sending messages to it are reported to the owning process using signals of the form {'EXIT', Port, PosixCode}. For the possible values of PosixCode, see file(3erl).

The maximum number of ports that can be open at the same time can be configured by passing command-line flag +Q to erl(1).

Types:

Portable hash function that gives the same hash for the same Erlang term regardless of machine architecture and ERTS version (the BIF was introduced in ERTS 4.9.1.1). The function returns a hash value for Term within the range 1..Range. The maximum value for Range is 2^32.

Types:

Portable hash function that gives the same hash for the same Erlang term regardless of machine architecture and ERTS version (the BIF was introduced in ERTS 5.2). The function returns a hash value for Term within the range 0..Range-1. The maximum value for Range is 2^32. When without argument Range, a value in the range 0..2^27-1 is returned.

This BIF is always to be used for hashing terms. It distributes small integers better than phash/2, and it is faster for bignums and binaries.

Notice that the range 0..Range-1 is different from the range of phash/2, which is 1..Range.

Types:

Returns a string corresponding to the text representation of Pid. Example:

> erlang:pid_to_list(self()).
"<0.85.0>"

Types:

Performs a synchronous call to a port. The meaning of Operation and Data depends on the port, that is, on the port driver. Not all port drivers support this feature.

Port is a port identifier, referring to a driver.

Operation is an integer, which is passed on to the driver.

Data is any Erlang term. This data is converted to binary term format and sent to the port.

Returns a term from the driver. The meaning of the returned data also depends on the port driver.

Failures:

Types:

Closes an open port. Roughly the same as Port ! {self(), close} except for the error behavior (see below), being synchronous, and that the port does not reply with {Port, closed}. Any process can close a port with port_close/1, not only the port owner (the connected process). If the calling process is linked to the port identified by Port, the exit signal from the port is guaranteed to be delivered before port_close/1 returns.

For comparison: Port ! {self(), close} only fails with badarg if Port does not refer to a port or a process. If Port is a closed port, nothing happens. If Port is an open port and the calling process is the port owner, the port replies with {Port, closed} when all buffers have been flushed and the port really closes. If the calling process is not the port owner, the port owner fails with badsig.

Notice that any process can close a port using Port ! {PortOwner, close} as if it itself was the port owner, but the reply always goes to the port owner.

As from Erlang/OTP R16, Port ! {PortOwner, close} is truly asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. port_close/1 is however still fully synchronous because of its error behavior.

Failure: badarg if Port is not an identifier of an open port, or the registered name of an open port. If the calling process was previously linked to the closed port, identified by Port, the exit signal from the port is guaranteed to be delivered before this badarg exception occurs.

Types:

Sends data to a port. Same as Port ! {PortOwner, {command, Data}} except for the error behavior and being synchronous (see below). Any process can send data to a port with port_command/2, not only the port owner (the connected process).

For comparison: Port ! {PortOwner, {command, Data}} only fails with badarg if Port does not refer to a port or a process. If Port is a closed port, the data message disappears without a sound. If Port is open and the calling process is not the port owner, the port owner fails with badsig. The port owner fails with badsig also if Data is an invalid I/O list.

Notice that any process can send to a port using Port ! {PortOwner, {command, Data}} as if it itself was the port owner.

If the port is busy, the calling process is suspended until the port is not busy any more.

As from Erlang/OTP R16, Port ! {PortOwner, {command, Data}} is truly asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. port_command/2 is however still fully synchronous because of its error behavior.

Failures:

Types:

Sends data to a port. port_command(Port, Data, []) equals port_command(Port, Data).

If the port command is aborted, false is returned, otherwise true.

If the port is busy, the calling process is suspended until the port is not busy anymore.

Options:

Failures:

Types:

Sets the port owner (the connected port) to Pid. Roughly the same as Port ! {Owner, {connect, Pid}} except for the following:

The old port owner stays linked to the port and must call unlink(Port) if this is not desired. Any process can set the port owner to be any process with port_connect/2.

For comparison: Port ! {self(), {connect, Pid}} only fails with badarg if Port does not refer to a port or a process. If Port is a closed port, nothing happens. If Port is an open port and the calling process is the port owner, the port replies with {Port, connected} to the old port owner. Notice that the old port owner is still linked to the port, while the new is not. If Port is an open port and the calling process is not the port owner, the port owner fails with badsig. The port owner fails with badsig also if Pid is not an existing local process identifier.

Notice that any process can set the port owner using Port ! {PortOwner, {connect, Pid}} as if it itself was the port owner, but the reply always goes to the port owner.

As from Erlang/OTP R16, Port ! {PortOwner, {connect, Pid}} is truly asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. port_connect/2 is however still fully synchronous because of its error behavior.

Failures:

Types:

Performs a synchronous control operation on a port. The meaning of Operation and Data depends on the port, that is, on the port driver. Not all port drivers support this control feature.

Returns a list of integers in the range 0..255, or a binary, depending on the port driver. The meaning of the returned data also depends on the port driver.

Failures:

Types:

Returns a list containing tuples with information about Port, or undefined if the port is not open. The order of the tuples is undefined, and all the tuples are not mandatory. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/1 returns undefined.

The result contains information about the following Items:

For more information about the different Items, see port_info/2.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Pid is the process identifier of the process connected to the port.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Index is the internal index of the port. This index can be used to separate ports.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Bytes is the total number of bytes read from the port.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Pids is a list of the process identifiers of the processes that the port is linked to.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Locking is one of the following:

Notice that these results are highly implementation-specific and can change in a future release.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Bytes is the total number of bytes allocated for this port by the runtime system. The port itself can have allocated memory that is not included in Bytes.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Monitors represent processes monitored by this port.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Returns list of pids that are monitoring given port at the moment.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Name is the command name set by open_port/2.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

OsPid is the process identifier (or equivalent) of an OS process created with open_port({spawn | spawn_executable, Command}, Options). If the port is not the result of spawning an OS process, the value is undefined.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Bytes is the total number of bytes written to the port from Erlang processes using port_command/2, port_command/3, or Port ! {Owner, {command, Data}.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Boolean corresponds to the port parallelism hint used by this port. For more information, see option parallelism of open_port/2.

Types:

Bytes is the total number of bytes queued by the port using the ERTS driver queue implementation.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

RegisteredName is the registered name of the port. If the port has no registered name, [] is returned.

If the port identified by Port is not open, undefined is returned. If the port is closed and the calling process was previously linked to the port, the exit signal from the port is guaranteed to be delivered before port_info/2 returns undefined.

Failure: badarg if Port is not a local port identifier, or an atom.

Types:

Returns a string corresponding to the text representation of the port identifier Port.

Returns a list of port identifiers corresponding to all the ports existing on the local node.

Notice that an exiting port exists, but is not open.

Returns a list of Erlang modules that are preloaded in the run-time system. Pre-loaded modules are Erlang modules that are needed to bootstrap the system to load the first Erlang modules from either disk or by using erl_boot_server.

Types:

Writes information about the local process Pid on standard error. The only allowed value for the atom Type is backtrace, which shows the contents of the call stack, including information about the call chain, with the current function printed first. The format of the output is not further defined.

Types:

When trap_exit is set to true, exit signals arriving to a process are converted to {'EXIT', From, Reason} messages, which can be received as ordinary messages. If trap_exit is set to false, the process exits if it receives an exit signal other than normal and the exit signal is propagated to its linked processes. Application processes are normally not to trap exits.

Returns the old value of the flag.

See also exit/2.

Types:

Used by a process to redefine the error handler for undefined function calls and undefined registered processes. Inexperienced users are not to use this flag, as code auto-loading depends on the correct operation of the error handling module.

Returns the old value of the flag.

Types:

Changes the maximum number of generational collections before forcing a fullsweep for the calling process.

Returns the old value of the flag.

Types:

Changes the minimum heap size for the calling process.

Returns the old value of the flag.

Types:

Changes the minimum binary virtual heap size for the calling process.

Returns the old value of the flag.

Types:

max_heap_size() = 


    integer() >= 0 |


    #{size => integer() >= 0,


      kill => boolean(),


      error_logger => boolean()}

This flag sets the maximum heap size for the calling process. If MaxHeapSize is an integer, the system default values for kill and error_logger are used.

For details on how the heap grows, see Sizing the heap in the ERTS internal documentation.

The heap size of a process is quite hard to predict, especially the amount of memory that is used during the garbage collection. When contemplating using this option, it is recommended to first run it in production with kill set to false and inspect the log events to see what the normal peak sizes of the processes in the system is and then tune the value accordingly.

Types:

message_queue_data() = off_heap | on_heap

Determines how messages in the message queue are stored, as follows:

The default value of the message_queue_data process flag is determined by the command-line argument +hmqd in erl(1).

If the process may potentially accumulate a large number of messages in its queue it is recommended to set the flag value to off_heap. This is due to the fact that the garbage collection of a process that has a large number of messages stored on the heap can become extremely expensive and the process can consume large amounts of memory. The performance of the actual message passing is, however, generally better when the flag value is on_heap.

Changing the flag value causes any existing messages to be moved. The move operation is initiated, but not necessarily completed, by the time the function returns.

Returns the old value of the flag.

Types:

priority_level() = low | normal | high | max

Sets the process priority. Level is an atom. Four priority levels exist: low, normal, high, and max. Default is normal.

Internally in each priority level, processes are scheduled in a round robin fashion.

Execution of processes on priority normal and low are interleaved. Processes on priority low are selected for execution less frequently than processes on priority normal.

When runnable processes on priority high exist, no processes on priority low or normal are selected for execution. Notice however that this does not mean that no processes on priority low or normal can run when processes are running on priority high. When using multiple schedulers, more processes can be running in parallel than processes on priority high. That is, a low and a high priority process can execute at the same time.

When runnable processes on priority max exist, no processes on priority low, normal, or high are selected for execution. As with priority high, processes on lower priorities can execute in parallel with processes on priority max.

Scheduling is pre-emptive. Regardless of priority, a process is pre-empted when it has consumed more than a certain number of reductions since the last time it was selected for execution.

There is no automatic mechanism for avoiding priority inversion, such as priority inheritance or priority ceilings. When using priorities, take this into account and handle such scenarios by yourself.

Making calls from a high priority process into code that you has no control over can cause the high priority process to wait for a process with lower priority. That is, effectively decreasing the priority of the high priority process during the call. Even if this is not the case with one version of the code that you have no control over, it can be the case in a future version of it. This can, for example, occur if a high priority process triggers code loading, as the code server runs on priority normal.

Other priorities than normal are normally not needed. When other priorities are used, use them with care, especially priority high. A process on priority high is only to perform work for short periods. Busy looping for long periods in a high priority process causes most likely problems, as important OTP servers run on priority normal.

Returns the old value of the flag.

Types:

N must be an integer in the interval 0..10000. If N > 0, call saving is made active for the process. This means that information about the N most recent global function calls, BIF calls, sends, and receives made by the process are saved in a list, which can be retrieved with process_info(Pid, last_calls). A global function call is one in which the module of the function is explicitly mentioned. Only a fixed amount of information is saved, as follows:

If N = 0, call saving is disabled for the process, which is the default. Whenever the size of the call saving list is set, its contents are reset.

Returns the old value of the flag.

Types:

Sets or clears flag sensitive for the current process. When a process has been marked as sensitive by calling process_flag(sensitive, true), features in the runtime system that can be used for examining the data or inner working of the process are silently disabled.

Features that are disabled include (but are not limited to) the following:

process_info/1,2 cannot be used to read out the message queue or the process dictionary (both are returned as empty lists).

Stack back-traces cannot be displayed for the process.

In crash dumps, the stack, messages, and the process dictionary are omitted.

If {save_calls,N} has been set for the process, no function calls are saved to the call saving list. (The call saving list is not cleared. Also, send, receive, and time-out events are still added to the list.)

Returns the old value of the flag.

Types:

Sets certain flags for the process Pid, in the same manner as process_flag/2. Returns the old value of the flag. The valid values for Flag are only a subset of those allowed in process_flag/2, namely save_calls.

Failure: badarg if Pid is not a local process.

Types:

process_info_result_item() = 


    {backtrace, Bin :: binary()} |


    {binary,


     BinInfo ::


         [{integer() >= 0,


           integer() >= 0,


           integer() >= 0}]} |


    {catchlevel, CatchLevel :: integer() >= 0} |


    {current_function,


     {Module :: module(), Function :: atom(), Arity :: arity()} |


     undefined} |


    {current_location,


     {Module :: module(),


      Function :: atom(),


      Arity :: arity(),


      Location ::


          [{file, Filename :: string()} |


           {line, Line :: integer() >= 1}]}} |


    {current_stacktrace, Stack :: [stack_item()]} |


    {dictionary, Dictionary :: [{Key :: term(), Value :: term()}]} |


    {error_handler, Module :: module()} |


    {garbage_collection, GCInfo :: [{atom(), integer() >= 0}]} |


    {garbage_collection_info,


     GCInfo :: [{atom(), integer() >= 0}]} |


    {group_leader, GroupLeader :: pid()} |


    {heap_size, Size :: integer() >= 0} |


    {initial_call, mfa()} |


    {links, PidsAndPorts :: [pid() | port()]} |


    {last_calls, false | (Calls :: [mfa()])} |


    {memory, Size :: integer() >= 0} |


    {message_queue_len, MessageQueueLen :: integer() >= 0} |


    {messages, MessageQueue :: [term()]} |


    {min_heap_size, MinHeapSize :: integer() >= 0} |


    {min_bin_vheap_size, MinBinVHeapSize :: integer() >= 0} |


    {max_heap_size, MaxHeapSize :: max_heap_size()} |


    {monitored_by,


     MonitoredBy :: [pid() | port() | nif_resource()]} |


    {monitors,


     Monitors ::


         [{process | port,


           Pid ::


               pid() |


               port() |


               {RegName :: atom(), Node :: node()}}]} |


    {message_queue_data, MQD :: message_queue_data()} |


    {parent, pid() | undefined} |


    {priority, Level :: priority_level()} |


    {reductions, Number :: integer() >= 0} |


    {registered_name, [] | (Atom :: atom())} |


    {sequential_trace_token,


     [] | (SequentialTraceToken :: term())} |


    {stack_size, Size :: integer() >= 0} |


    {status,


     Status ::


         exiting | garbage_collecting | waiting | running |


         runnable | suspended} |


    {suspending,


     SuspendeeList ::


         [{Suspendee :: pid(),


           ActiveSuspendCount :: integer() >= 0,


           OutstandingSuspendCount :: integer() >= 0}]} |


    {total_heap_size, Size :: integer() >= 0} |


    {trace, InternalTraceFlags :: integer() >= 0} |


    {trap_exit, Boolean :: boolean()}

priority_level() = low | normal | high | max

stack_item() = 


    {Module :: module(),


     Function :: atom(),


     Arity :: arity() | (Args :: [term()]),


     Location ::


         [{file, Filename :: string()} |


          {line, Line :: integer() >= 1}]}

max_heap_size() = 


    integer() >= 0 |


    #{size => integer() >= 0,


      kill => boolean(),


      error_logger => boolean()}

message_queue_data() = off_heap | on_heap

Returns a list containing InfoTuples with miscellaneous information about the process identified by Pid, or undefined if the process is not alive.

The order of the InfoTuples is undefined and all InfoTuples are not mandatory. The InfoTuples part of the result can be changed without prior notice.

The InfoTuples with the following items are part of the result:

If the process identified by Pid has a registered name, also an InfoTuple with item registered_name is included.

For information about specific InfoTuples, see process_info/2.

Failure: badarg if Pid is not a local process.

Types:

process_info_item() = 


    backtrace | binary | catchlevel | current_function |


    current_location | current_stacktrace | dictionary |


    error_handler | garbage_collection | garbage_collection_info |


    group_leader | heap_size | initial_call | links | last_calls |


    memory | message_queue_len | messages | min_heap_size |


    min_bin_vheap_size | monitored_by | monitors |


    message_queue_data | parent | priority | reductions |


    registered_name | sequential_trace_token | stack_size |


    status | suspending | total_heap_size | trace | trap_exit

process_info_result_item() = 


    {backtrace, Bin :: binary()} |


    {binary,


     BinInfo ::


         [{integer() >= 0,


           integer() >= 0,


           integer() >= 0}]} |


    {catchlevel, CatchLevel :: integer() >= 0} |


    {current_function,


     {Module :: module(), Function :: atom(), Arity :: arity()} |


     undefined} |


    {current_location,


     {Module :: module(),


      Function :: atom(),


      Arity :: arity(),


      Location ::


          [{file, Filename :: string()} |


           {line, Line :: integer() >= 1}]}} |


    {current_stacktrace, Stack :: [stack_item()]} |


    {dictionary, Dictionary :: [{Key :: term(), Value :: term()}]} |


    {error_handler, Module :: module()} |


    {garbage_collection, GCInfo :: [{atom(), integer() >= 0}]} |


    {garbage_collection_info,


     GCInfo :: [{atom(), integer() >= 0}]} |


    {group_leader, GroupLeader :: pid()} |


    {heap_size, Size :: integer() >= 0} |


    {initial_call, mfa()} |


    {links, PidsAndPorts :: [pid() | port()]} |


    {last_calls, false | (Calls :: [mfa()])} |


    {memory, Size :: integer() >= 0} |


    {message_queue_len, MessageQueueLen :: integer() >= 0} |


    {messages, MessageQueue :: [term()]} |


    {min_heap_size, MinHeapSize :: integer() >= 0} |


    {min_bin_vheap_size, MinBinVHeapSize :: integer() >= 0} |


    {max_heap_size, MaxHeapSize :: max_heap_size()} |


    {monitored_by,


     MonitoredBy :: [pid() | port() | nif_resource()]} |


    {monitors,


     Monitors ::


         [{process | port,


           Pid ::


               pid() |


               port() |


               {RegName :: atom(), Node :: node()}}]} |


    {message_queue_data, MQD :: message_queue_data()} |


    {parent, pid() | undefined} |


    {priority, Level :: priority_level()} |


    {reductions, Number :: integer() >= 0} |


    {registered_name, [] | (Atom :: atom())} |


    {sequential_trace_token,


     [] | (SequentialTraceToken :: term())} |


    {stack_size, Size :: integer() >= 0} |


    {status,


     Status ::


         exiting | garbage_collecting | waiting | running |


         runnable | suspended} |


    {suspending,


     SuspendeeList ::


         [{Suspendee :: pid(),


           ActiveSuspendCount :: integer() >= 0,


           OutstandingSuspendCount :: integer() >= 0}]} |


    {total_heap_size, Size :: integer() >= 0} |


    {trace, InternalTraceFlags :: integer() >= 0} |


    {trap_exit, Boolean :: boolean()}

stack_item() = 


    {Module :: module(),


     Function :: atom(),


     Arity :: arity() | (Args :: [term()]),


     Location ::


         [{file, Filename :: string()} |


          {line, Line :: integer() >= 1}]}

priority_level() = low | normal | high | max

max_heap_size() = 


    integer() >= 0 |


    #{size => integer() >= 0,


      kill => boolean(),


      error_logger => boolean()}

message_queue_data() = off_heap | on_heap

Returns information about the process identified by Pid, as specified by Item or ItemList. Returns undefined if the process is not alive.

If the process is alive and a single Item is specified, the returned value is the corresponding InfoTuple, unless Item =:= registered_name and the process has no registered name. In this case, [] is returned. This strange behavior is because of historical reasons, and is kept for backward compatibility.

If ItemList is specified, the result is InfoTupleList. The InfoTuples in InfoTupleList are included with the corresponding Items in the same order as the Items were included in ItemList. Valid Items can be included multiple times in ItemList.

Getting process information follows the signal ordering guarantees described in the Processes Chapter in the Erlang Reference Manual .

Valid InfoTuples with corresponding Items:

Notice that not all implementations support all these Items.

Failures:

Returns a list of process identifiers corresponding to all the processes currently existing on the local node.

Notice that an exiting process exists, but is not alive. That is, is_process_alive/1 returns false for an exiting process, but its process identifier is part of the result returned from processes/0.

Example:

> processes().
[<0.0.0>,<0.2.0>,<0.4.0>,<0.5.0>,<0.7.0>,<0.8.0>]

Types:

Removes old code for Module. Before this BIF is used, check_process_code/2 is to be called to check that no processes execute old code in the module.

Failure: badarg if there is no old code for Module.

Types:

Adds a new Key to the process dictionary, associated with the value Val, and returns undefined. If Key exists, the old value is deleted and replaced by Val, and the function returns the old value. The average time complexity for the current implementation of this function is O(1) and the worst case time complexity is O(N), where N is the number of items in the process dictionary. Example:

> X = put(name, walrus), Y = put(name, carpenter),
Z = get(name),
{X, Y, Z}.
{undefined,walrus,carpenter}

Types:

raise_stacktrace() = 


    [{module(), atom(), arity() | [term()]} |


     {function(), arity() | [term()]}]

Raises an exception of the specified class, reason, and call stack backtrace (stacktrace).

Class is error, exit, or throw. So, if it were not for the stacktrace, erlang:raise(Class, Reason, Stacktrace) is equivalent to erlang:Class(Reason) (given that Class is a valid class).

Reason can be any term.

Stacktrace is a list as provided in a try-catch clause.

try


    ...
catch Class:Reason:Stacktrace ->


    ...
end

That is, a list of four-tuples {Module, Function, Arity | Args, ExtraInfo}, where Module and Function are atoms, and the third element is an integer arity or an argument list. The stacktrace can also contain {Fun, Args, ExtraInfo} tuples, where Fun is a local fun and Args is an argument list.

Element ExtraInfo at the end is optional. Omitting it is equivalent to specifying an empty list.

The stacktrace is used as the exception stacktrace for the calling process; it is truncated to the current maximum stacktrace depth.

As evaluating this function causes the process to terminate, it has no return value unless the arguments are invalid, in which case the function returns the error reason badarg. If you want to be sure not to return, you can call error(erlang:raise(Class, Reason, Stacktrace)) and hope to distinguish exceptions later.

See the reference manual about errors and error handling for more information about exception classes and how to catch exceptions.

Types: