erl
(1)
名前
erl - The Erlang Emulator
形式
Please see following description for synopsis
説明
User Commands erl(1)
NAME
erl - The Erlang Emulator
DESCRIPTION
The erl program starts an Erlang runtime system. The exact
details (for example, whether erl is a script or a program
and which other programs it calls) are system-dependent.
Windows users probably wants to use the werl program
instead, which runs in its own window with scrollbars and
supports command-line editing. The erl program on Windows
provides no line editing in its shell, and on Windows 95
there is no way to scroll back to text which has scrolled
off the screen. The erl program must be used, however, in
pipelines or if you want to redirect standard input or out-
put.
Note:
As of ERTS version 5.9 (OTP-R15B) the runtime system will by
default not bind schedulers to logical processors. For more
information see documentation of the +sbt system flag.
EXPORTS
erl <arguments>
Starts an Erlang runtime system.
The arguments can be divided into emulator flags, flags
and plain arguments:
* Any argument starting with the character + is
interpreted as an emulator flag.
As indicated by the name, emulator flags controls
the behavior of the emulator.
* Any argument starting with the character - (hyphen)
is interpreted as a flag which should be passed to
the Erlang part of the runtime system, more specif-
ically to the init system process, see init(3).
The init process itself interprets some of these
flags, the init flags. It also stores any remaining
flags, the user flags. The latter can be retrieved
by calling init:get_argument/1.
It can be noted that there are a small number of
"-" flags which now actually are emulator flags,
see the description below.
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User Commands erl(1)
* Plain arguments are not interpreted in any way.
They are also stored by the init process and can be
retrieved by calling init:get_plain_arguments/0.
Plain arguments can occur before the first flag, or
after a -- flag. Additionally, the flag -extra
causes everything that follows to become plain
arguments.
Example:
% erl +W w -sname arnie +R 9 -s my_init -extra +bertie
(arnie@host)1> init:get_argument(sname).
{ok,[["arnie"]]}
(arnie@host)2> init:get_plain_arguments().
["+bertie"]
Here +W w and +R 9 are emulator flags. -s my_init is an
init flag, interpreted by init. -sname arnie is a user
flag, stored by init. It is read by Kernel and will
cause the Erlang runtime system to become distributed.
Finally, everything after -extra (that is, +bertie) is
considered as plain arguments.
% erl -myflag 1
1> init:get_argument(myflag).
{ok,[["1"]]}
2> init:get_plain_arguments().
[]
Here the user flag -myflag 1 is passed to and stored by
the init process. It is a user defined flag, presumably
used by some user defined application.
FLAGS
In the following list, init flags are marked (init flag).
Unless otherwise specified, all other flags are user flags,
for which the values can be retrieved by calling
init:get_argument/1. Note that the list of user flags is not
exhaustive, there may be additional, application specific
flags which instead are documented in the corresponding
application documentation.
--(init flag):
Everything following -- up to the next flag (-flag or
+flag) is considered plain arguments and can be
retrieved using init:get_plain_arguments/0.
-Application Par Val:
Sets the application configuration parameter Par to the
value Val for the application Application, see app(4)
and application(3).
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User Commands erl(1)
-args_file FileName:
Command line arguments are read from the file FileName.
The arguments read from the file replace the '-args_file
FileName' flag on the resulting command line.
The file FileName should be a plain text file and may
contain comments and command line arguments. A comment
begins with a # character and continues until next end
of line character. Backslash (\\) is used as quoting
character. All command line arguments accepted by erl
are allowed, also the -args_file FileName flag. Be care-
ful not to cause circular dependencies between files
containing the -args_file flag, though.
The -extra flag is treated specially. Its scope ends at
the end of the file. Arguments following an -extra flag
are moved on the command line into the -extra section,
i.e. the end of the command line following after an
-extra flag.
-async_shell_start:
The initial Erlang shell does not read user input until
the system boot procedure has been completed (Erlang 5.4
and later). This flag disables the start synchronization
feature and lets the shell start in parallel with the
rest of the system.
-boot File:
Specifies the name of the boot file, File.boot, which is
used to start the system. See init(3). Unless File con-
tains an absolute path, the system searches for
File.boot in the current and $ROOT/bin directories.
Defaults to $ROOT/bin/start.boot.
-boot_var Var Dir:
If the boot script contains a path variable Var other
than $ROOT, this variable is expanded to Dir. Used when
applications are installed in another directory than
$ROOT/lib, see systools:make_script/1,2.
-code_path_cache:
Enables the code path cache of the code server, see
code(3).
-compile Mod1 Mod2 ...:
Compiles the specified modules and then terminates (with
non-zero exit code if the compilation of some file did
not succeed). Implies -noinput. Not recommended - use
erlc instead.
-config Config:
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User Commands erl(1)
Specifies the name of a configuration file, Config.con-
fig, which is used to configure applications. See app(4)
and application(3).
-connect_all false:
If this flag is present, global will not maintain a
fully connected network of distributed Erlang nodes, and
then global name registration cannot be used. See
global(3).
-cookie Cookie:
Obsolete flag without any effect and common misspelling
for -setcookie. Use -setcookie instead.
-detached:
Starts the Erlang runtime system detached from the sys-
tem console. Useful for running daemons and backgrounds
processes. Implies -noinput.
-emu_args:
Useful for debugging. Prints out the actual arguments
sent to the emulator.
-env Variable Value:
Sets the host OS environment variable Variable to the
value Value for the Erlang runtime system. Example:
% erl -env DISPLAY gin:0
In this example, an Erlang runtime system is started
with the DISPLAY environment variable set to gin:0.
-eval Expr(init flag):
Makes init evaluate the expression Expr, see init(3).
-extra(init flag):
Everything following -extra is considered plain argu-
ments and can be retrieved using init:get_plain_argu-
ments/0.
-heart:
Starts heart beat monitoring of the Erlang runtime sys-
tem. See heart(3).
-hidden:
Starts the Erlang runtime system as a hidden node, if it
is run as a distributed node. Hidden nodes always estab-
lish hidden connections to all other nodes except for
nodes in the same global group. Hidden connections are
not published on either of the connected nodes, i.e.
neither of the connected nodes are part of the result
from nodes/0 on the other node. See also hidden global
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User Commands erl(1)
groups, global_group(3).
-hosts Hosts:
Specifies the IP addresses for the hosts on which Erlang
boot servers are running, see erl_boot_server(3). This
flag is mandatory if the -loader inet flag is present.
The IP addresses must be given in the standard form
(four decimal numbers separated by periods, for example
"150.236.20.74". Hosts names are not acceptable, but a
broadcast address (preferably limited to the local net-
work) is.
-id Id:
Specifies the identity of the Erlang runtime system. If
it is run as a distributed node, Id must be identical to
the name supplied together with the -sname or -name
flag.
-init_debug:
Makes init write some debug information while interpret-
ing the boot script.
-instr(emulator flag):
Selects an instrumented Erlang runtime system (virtual
machine) to run, instead of the ordinary one. When run-
ning an instrumented runtime system, some resource usage
data can be obtained and analysed using the module
instrument. Functionally, it behaves exactly like an
ordinary Erlang runtime system.
-loader Loader:
Specifies the method used by erl_prim_loader to load
Erlang modules into the system. See erl_prim_loader(3).
Two Loader methods are supported, efile and inet. efile
means use the local file system, this is the default.
inet means use a boot server on another machine, and the
-id, -hosts and -setcookie flags must be specified as
well. If Loader is something else, the user supplied
Loader port program is started.
-make:
Makes the Erlang runtime system invoke make:all() in the
current working directory and then terminate. See
make(3). Implies -noinput.
-man Module:
Displays the manual page for the Erlang module Module.
Only supported on Unix.
-mode interactive | embedded:
Indicates if the system should load code dynamically
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User Commands erl(1)
(interactive), or if all code should be loaded during
system initialization (embedded), see code(3). Defaults
to interactive.
-name Name:
Makes the Erlang runtime system into a distributed node.
This flag invokes all network servers necessary for a
node to become distributed. See net_kernel(3). It is
also ensured that epmd runs on the current host before
Erlang is started. See epmd(1).
The name of the node will be Name@Host, where Host is
the fully qualified host name of the current host. For
short names, use the -sname flag instead.
-noinput:
Ensures that the Erlang runtime system never tries to
read any input. Implies -noshell.
-noshell:
Starts an Erlang runtime system with no shell. This flag
makes it possible to have the Erlang runtime system as a
component in a series of UNIX pipes.
-nostick:
Disables the sticky directory facility of the Erlang
code server, see code(3).
-oldshell:
Invokes the old Erlang shell from Erlang 3.3. The old
shell can still be used.
-pa Dir1 Dir2 ...:
Adds the specified directories to the beginning of the
code path, similar to code:add_pathsa/1. See code(3). As
an alternative to -pa, if several directories are to be
prepended to the code and the directories have a common
parent directory, that parent directory could be speci-
fied in the ERL_LIBS environment variable. See code(3).
-pz Dir1 Dir2 ...:
Adds the specified directories to the end of the code
path, similar to code:add_pathsz/1. See code(3).
-remsh Node:
Starts Erlang with a remote shell connected to Node.
-rsh Program:
Specifies an alternative to rsh for starting a slave
node on a remote host. See slave(3).
-run Mod [Func [Arg1, Arg2, ...]](init flag):
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User Commands erl(1)
Makes init call the specified function. Func defaults to
start. If no arguments are provided, the function is
assumed to be of arity 0. Otherwise it is assumed to be
of arity 1, taking the list [Arg1,Arg2,...] as argument.
All arguments are passed as strings. See init(3).
-s Mod [Func [Arg1, Arg2, ...]](init flag):
Makes init call the specified function. Func defaults to
start. If no arguments are provided, the function is
assumed to be of arity 0. Otherwise it is assumed to be
of arity 1, taking the list [Arg1,Arg2,...] as argument.
All arguments are passed as atoms. See init(3).
-setcookie Cookie:
Sets the magic cookie of the node to Cookie, see
erlang:set_cookie/2.
-shutdown_time Time:
Specifies how long time (in milliseconds) the init
process is allowed to spend shutting down the system. If
Time ms have elapsed, all processes still existing are
killed. Defaults to infinity.
-sname Name:
Makes the Erlang runtime system into a distributed node,
similar to -name, but the host name portion of the node
name Name@Host will be the short name, not fully quali-
fied.
This is sometimes the only way to run distributed Erlang
if the DNS (Domain Name System) is not running. There
can be no communication between nodes running with the
-sname flag and those running with the -name flag, as
node names must be unique in distributed Erlang systems.
-smp [enable|auto|disable]:
-smp enable and -smp starts the Erlang runtime system
with SMP support enabled. This may fail if no runtime
system with SMP support is available. -smp auto starts
the Erlang runtime system with SMP support enabled if it
is available and more than one logical processor are
detected. -smp disable starts a runtime system without
SMP support.
NOTE: The runtime system with SMP support will not be
available on all supported platforms. See also the +S
flag.
-version(emulator flag):
Makes the emulator print out its version number. The
same as erl +V.
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User Commands erl(1)
EMULATOR FLAGS
erl invokes the code for the Erlang emulator (virtual
machine), which supports the following flags:
+a size:
Suggested stack size, in kilowords, for threads in the
async-thread pool. Valid range is 16-8192 kilowords. The
default suggested stack size is 16 kilowords, i.e, 64
kilobyte on 32-bit architectures. This small default
size has been chosen since the amount of async-threads
might be quite large. The default size is enough for
drivers delivered with Erlang/OTP, but might not be suf-
ficiently large for other dynamically linked in drivers
that use the driver_async() functionality. Note that the
value passed is only a suggestion, and it might even be
ignored on some platforms.
+A size:
Sets the number of threads in async thread pool, valid
range is 0-1024. Default is 0.
+B [c | d | i]:
The c option makes Ctrl-C interrupt the current shell
instead of invoking the emulator break handler. The d
option (same as specifying +B without an extra option)
disables the break handler. The i option makes the emu-
lator ignore any break signal.
If the c option is used with oldshell on Unix, Ctrl-C
will restart the shell process rather than interrupt it.
Note that on Windows, this flag is only applicable for
werl, not erl (oldshell). Note also that Ctrl-Break is
used instead of Ctrl-C on Windows.
+c:
Disable compensation for sudden changes of system time.
Normally, erlang:now/0 will not immediately reflect sud-
den changes in the system time, in order to keep timers
(including receive-after) working. Instead, the time
maintained by erlang:now/0 is slowly adjusted towards
the new system time. (Slowly means in one percent
adjustments; if the time is off by one minute, the time
will be adjusted in 100 minutes.)
When the +c option is given, this slow adjustment will
not take place. Instead erlang:now/0 will always reflect
the current system time. Note that timers are based on
erlang:now/0. If the system time jumps, timers then time
out at the wrong time.
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User Commands erl(1)
+d:
If the emulator detects an internal error (or runs out
of memory), it will by default generate both a crash
dump and a core dump. The core dump will, however, not
be very useful since the content of process heaps is
destroyed by the crash dump generation.
The +d option instructs the emulator to only produce a
core dump and no crash dump if an internal error is
detected.
Calling erlang:halt/1 with a string argument will still
produce a crash dump.
+e Number:
Set max number of ETS tables.
+ec:
Force the compressed option on all ETS tables. Only
intended for test and evaluation.
+fnl:
The VM works with file names as if they are encoded
using the ISO-latin-1 encoding, disallowing Unicode
characters with codepoints beyond 255. This is default
on operating systems that have transparent file naming,
i.e. all Unixes except MacOSX.
+fnu:
The VM works with file names as if they are encoded
using UTF-8 (or some other system specific Unicode
encoding). This is the default on operating systems that
enforce Unicode encoding, i.e. Windows and MacOSX.
By enabling Unicode file name translation on systems
where this is not default, you open up to the possibil-
ity that some file names can not be interpreted by the
VM and therefore will be returned to the program as raw
binaries. The option is therefore considered experimen-
tal.
+fna:
Selection between +fnl and +fnu is done based on the
current locale settings in the OS, meaning that if you
have set your terminal for UTF-8 encoding, the filesys-
tem is expected to use the same encoding for filenames
(use with care).
+hms Size:
Sets the default heap size of processes to the size
Size.
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User Commands erl(1)
+hmbs Size:
Sets the default binary virtual heap size of processes
to the size Size.
+K true | false:
Enables or disables the kernel poll functionality if the
emulator supports it. Default is false (disabled). If
the emulator does not support kernel poll, and the +K
flag is passed to the emulator, a warning is issued at
startup.
+l:
Enables auto load tracing, displaying info while loading
code.
+L:
Don't load information about source filenames and line
numbers. This will save some memory, but exceptions will
not contain information about the filenames and line
numbers.
+MFlag Value:
Memory allocator specific flags, see erts_alloc(3) for
further information.
+P Number:
Sets the maximum number of concurrent processes for this
system. Number must be in the range 16..134217727.
Default is 32768.
+R ReleaseNumber:
Sets the compatibility mode.
The distribution mechanism is not backwards compatible
by default. This flags sets the emulator in compatibil-
ity mode with an earlier Erlang/OTP release ReleaseNum-
ber. The release number must be in the range 7..<current
release>. This limits the emulator, making it possible
for it to communicate with Erlang nodes (as well as C-
and Java nodes) running that earlier release.
For example, an R10 node is not automatically compatible
with an R9 node, but R10 nodes started with the +R 9
flag can co-exist with R9 nodes in the same distributed
Erlang system, they are R9-compatible.
Note: Make sure all nodes (Erlang-, C-, and Java nodes)
of a distributed Erlang system is of the same Erlang/OTP
release, or from two different Erlang/OTP releases X and
Y, where all Y nodes have compatibility mode X.
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User Commands erl(1)
For example: A distributed Erlang system can consist of
R10 nodes, or of R9 nodes and R9-compatible R10 nodes,
but not of R9 nodes, R9-compatible R10 nodes and "regu-
lar" R10 nodes, as R9 and "regular" R10 nodes are not
compatible.
+r:
Force ets memory block to be moved on realloc.
+rg ReaderGroupsLimit:
Limits the amount of reader groups used by read/write
locks optimized for read operations in the Erlang run-
time system. By default the reader groups limit equals
8.
When the amount of schedulers is less than or equal to
the reader groups limit, each scheduler has its own
reader group. When the amount of schedulers is larger
than the reader groups limit, schedulers share reader
groups. Shared reader groups degrades read lock and read
unlock performance while a large amount of reader groups
degrades write lock performance, so the limit is a
tradeoff between performance for read operations and
performance for write operations. Each reader group cur-
rently consumes 64 byte in each read/write lock. Also
note that a runtime system using shared reader groups
benefits from binding schedulers to logical processors,
since the reader groups are distributed better between
schedulers.
+S Schedulers:SchedulerOnline:
Sets the amount of scheduler threads to create and
scheduler threads to set online when SMP support has
been enabled. Valid range for both values are 1-1024. If
the Erlang runtime system is able to determine the
amount of logical processors configured and logical pro-
cessors available, Schedulers will default to logical
processors configured, and SchedulersOnline will default
to logical processors available; otherwise, the default
values will be 1. Schedulers may be omitted if :Sched-
ulerOnline is not and vice versa. The amount of sched-
ulers online can be changed at run time via erlang:sys-
tem_flag(schedulers_online, SchedulersOnline).
This flag will be ignored if the emulator doesn't have
SMP support enabled (see the -smp flag).
+sFlag Value:
Scheduling specific flags.
+sbt BindType:
Set scheduler bind type. Currently valid BindTypes:
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User Commands erl(1)
u:
unbound - Schedulers will not be bound to logical
processors, i.e., the operating system decides where
the scheduler threads execute, and when to migrate
them. This is the default.
ns:
no_spread - Schedulers with close scheduler identi-
fiers will be bound as close as possible in hard-
ware.
ts:
thread_spread - Thread refers to hardware threads
(e.g. Intel's hyper-threads). Schedulers with low
scheduler identifiers, will be bound to the first
hardware thread of each core, then schedulers with
higher scheduler identifiers will be bound to the
second hardware thread of each core, etc.
ps:
processor_spread - Schedulers will be spread like
thread_spread, but also over physical processor
chips.
s:
spread - Schedulers will be spread as much as possi-
ble.
nnts:
no_node_thread_spread - Like thread_spread, but if
multiple NUMA (Non-Uniform Memory Access) nodes
exists, schedulers will be spread over one NUMA node
at a time, i.e., all logical processors of one NUMA
node will be bound to schedulers in sequence.
nnps:
no_node_processor_spread - Like processor_spread,
but if multiple NUMA nodes exists, schedulers will
be spread over one NUMA node at a time, i.e., all
logical processors of one NUMA node will be bound to
schedulers in sequence.
tnnps:
thread_no_node_processor_spread - A combination of
thread_spread, and no_node_processor_spread. Sched-
ulers will be spread over hardware threads across
NUMA nodes, but schedulers will only be spread over
processors internally in one NUMA node at a time.
db:
default_bind - Binds schedulers the default way.
Currently the default is
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User Commands erl(1)
thread_no_node_processor_spread (which might change
in the future).
Binding of schedulers is currently only supported on
newer Linux, Solaris, FreeBSD, and Windows systems.
If no CPU topology is available when the +sbt flag is
processed and BindType is any other type than u, the
runtime system will fail to start. CPU topology can be
defined using the +sct flag. Note that the +sct flag
may have to be passed before the +sbt flag on the com-
mand line (in case no CPU topology has been automati-
cally detected).
The runtime system will by default not bind schedulers
to logical processors.
NOTE: If the Erlang runtime system is the only operat-
ing system process that binds threads to logical pro-
cessors, this improves the performance of the runtime
system. However, if other operating system processes
(as for example another Erlang runtime system) also
bind threads to logical processors, there might be a
performance penalty instead. In some cases this per-
formance penalty might be severe. If this is the case,
you are advised to not bind the schedulers.
How schedulers are bound matters. For example, in sit-
uations when there are fewer running processes than
schedulers online, the runtime system tries to migrate
processes to schedulers with low scheduler identi-
fiers. The more the schedulers are spread over the
hardware, the more resources will be available to the
runtime system in such situations.
NOTE: If a scheduler fails to bind, this will often be
silently ignored. This since it isn't always possible
to verify valid logical processor identifiers. If an
error is reported, it will be reported to the
error_logger. If you want to verify that the sched-
ulers actually have bound as requested, call
erlang:system_info(scheduler_bindings).
+sbwt none|very_short|short|medium|long|very_long:
Set scheduler busy wait threshold. Default is medium.
The threshold determines how long schedulers should
busy wait when running out of work before going to
sleep.
NOTE: This flag may be removed or changed at any time
without prior notice.
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User Commands erl(1)
+scl true|false:
Enable or disable scheduler compaction of load. By
default scheduler compaction of load is enabled. When
enabled, load balancing will strive for a load distri-
bution which causes as many scheduler threads as pos-
sible to be fully loaded (i.e., not run out of work).
This is accomplished by migrating load (e.g. runnable
processes) into a smaller set of schedulers when
schedulers frequently run out of work. When disabled,
the frequency with which schedulers run out of work
will not be taken into account by the load balancing
logic.
+sct CpuTopology:
* <Id> = integer(); when 0 =< <Id> =< 65535
* <IdRange> = <Id>-<Id>
* <IdOrIdRange> = <Id> | <IdRange>
* <IdList> = <IdOrIdRange>,<IdOrIdRange> |
<IdOrIdRange>
* <LogicalIds> = L<IdList>
* <ThreadIds> = T<IdList> | t<IdList>
* <CoreIds> = C<IdList> | c<IdList>
* <ProcessorIds> = P<IdList> | p<IdList>
* <NodeIds> = N<IdList> | n<IdList>
* <IdDefs> = <LogicalIds><ThreadIds><CoreIds><Proces-
sorIds><NodeIds> | <LogicalIds><ThreadIds><Cor-
eIds><NodeIds><ProcessorIds>
* CpuTopology = <IdDefs>:<IdDefs> | <IdDefs>
Set a user defined CPU topology. The user defined CPU
topology will override any automatically detected CPU
topology. The CPU topology is used when binding sched-
ulers to logical processors.
Upper-case letters signify real identifiers and lower-
case letters signify fake identifiers only used for
description of the topology. Identifiers passed as
real identifiers may be used by the runtime system
when trying to access specific hardware and if they
are not correct the behavior is undefined. Faked
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User Commands erl(1)
logical CPU identifiers are not accepted since there
is no point in defining the CPU topology without real
logical CPU identifiers. Thread, core, processor, and
node identifiers may be left out. If left out, thread
id defaults to t0, core id defaults to c0, processor
id defaults to p0, and node id will be left undefined.
Either each logical processor must belong to one and
only one NUMA node, or no logical processors must
belong to any NUMA nodes.
Both increasing and decreasing <IdRange>s are allowed.
NUMA node identifiers are system wide. That is, each
NUMA node on the system have to have a unique identi-
fier. Processor identifiers are also system wide. Core
identifiers are processor wide. Thread identifiers are
core wide.
The order of the identifier types imply the hierarchy
of the CPU topology. Valid orders are either <Logi-
calIds><ThreadIds><CoreIds><ProcessorIds><NodeIds>, or
<LogicalIds><ThreadIds><CoreIds><NodeIds><Proces-
sorIds>. That is, thread is part of a core which is
part of a processor which is part of a NUMA node, or
thread is part of a core which is part of a NUMA node
which is part of a processor. A cpu topology can con-
sist of both processor external, and processor inter-
nal NUMA nodes as long as each logical processor
belongs to one and only one NUMA node. If <Proces-
sorIds> is left out, its default position will be
before <NodeIds>. That is, the default is processor
external NUMA nodes.
If a list of identifiers is used in an <IdDefs>:
* <LogicalIds> have to be a list of identifiers.
* At least one other identifier type apart from <Logi-
calIds> also have to have a list of identifiers.
* All lists of identifiers have to produce the same
amount of identifiers.
A simple example. A single quad core processor may be
described this way:
% erl +sct L0-3c0-3
1> erlang:system_info(cpu_topology).
[{processor,[{core,{logical,0}},
{core,{logical,1}},
{core,{logical,2}},
{core,{logical,3}}]}]
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User Commands erl(1)
A little more complicated example. Two quad core pro-
cessors. Each processor in its own NUMA node. The
ordering of logical processors is a little weird. This
in order to give a better example of identifier lists:
% erl +sct L0-1,3-2c0-3p0N0:L7,4,6-5c0-3p1N1
1> erlang:system_info(cpu_topology).
[{node,[{processor,[{core,{logical,0}},
{core,{logical,1}},
{core,{logical,3}},
{core,{logical,2}}]}]},
{node,[{processor,[{core,{logical,7}},
{core,{logical,4}},
{core,{logical,6}},
{core,{logical,5}}]}]}]
As long as real identifiers are correct it is okay to
pass a CPU topology that is not a correct description
of the CPU topology. When used with care this can
actually be very useful. This in order to trick the
emulator to bind its schedulers as you want. For exam-
ple, if you want to run multiple Erlang runtime sys-
tems on the same machine, you want to reduce the
amount of schedulers used and manipulate the CPU
topology so that they bind to different logical CPUs.
An example, with two Erlang runtime systems on a quad
core machine:
% erl +sct L0-3c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname one
% erl +sct L3-0c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname two
In this example each runtime system have two sched-
ulers each online, and all schedulers online will run
on different cores. If we change to one scheduler
online on one runtime system, and three schedulers
online on the other, all schedulers online will still
run on different cores.
Note that a faked CPU topology that does not reflect
how the real CPU topology looks like is likely to
decrease the performance of the runtime system.
For more information, see erlang:sys-
tem_info(cpu_topology).
+sws default|legacy|proposal:
Set scheduler wakeup strategy. Default is legacy (has
been used since OTP-R13B). The proposal strategy is
the currently proposed strategy for OTP-R16. Note that
the proposal strategy might change during OTP-R15.
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User Commands erl(1)
NOTE: This flag may be removed or changed at any time
without prior notice.
+swt very_low|low|medium|high|very_high:
Set scheduler wakeup threshold. Default is medium. The
threshold determines when to wake up sleeping sched-
ulers when more work than can be handled by currently
awake schedulers exist. A low threshold will cause
earlier wakeups, and a high threshold will cause later
wakeups. Early wakeups will distribute work over mul-
tiple schedulers faster, but work will more easily
bounce between schedulers.
NOTE: This flag may be removed or changed at any time
without prior notice.
+sss size:
Suggested stack size, in kilowords, for scheduler
threads. Valid range is 4-8192 kilowords. The default
stack size is OS dependent.
+t size:
Set the maximum number of atoms the VM can handle.
Default is 1048576.
+T Level:
Enables modified timing and sets the modified timing
level. Currently valid range is 0-9. The timing of the
runtime system will change. A high level usually means a
greater change than a low level. Changing the timing can
be very useful for finding timing related bugs.
Currently, modified timing affects the following:
Process spawning:
A process calling spawn, spawn_link, spawn_monitor, or
spawn_opt will be scheduled out immediately after com-
pleting the call. When higher modified timing levels
are used, the caller will also sleep for a while after
being scheduled out.
Context reductions:
The amount of reductions a process is a allowed to use
before being scheduled out is increased or reduced.
Input reductions:
The amount of reductions performed before checking I/O
is increased or reduced.
NOTE: Performance will suffer when modified timing is
enabled. This flag is only intended for testing and
debugging. Also note that return_to and return_from
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User Commands erl(1)
trace messages will be lost when tracing on the spawn
BIFs. This flag may be removed or changed at any time
without prior notice.
+V:
Makes the emulator print out its version number.
+v:
Verbose.
+W w | i:
Sets the mapping of warning messages for error_logger.
Messages sent to the error logger using one of the warn-
ing routines can be mapped either to errors (default),
warnings (+W w), or info reports (+W i). The current
mapping can be retrieved using error_logger:warn-
ing_map/0. See error_logger(3) for further information.
+zFlag Value:
Miscellaneous flags.
+zdbbl size:
Set the distribution buffer busy limit
(dist_buf_busy_limit) in kilobytes. Valid range is
1-2097151. Default is 1024.
A larger buffer limit will allow processes to buffer
more outgoing messages over the distribution. When the
buffer limit has been reached, sending processes will
be suspended until the buffer size has shrunk. The
buffer limit is per distribution channel. A higher
limit will give lower latency and higher throughput at
the expense of higher memory usage.
ENVIRONMENT VARIABLES
ERL_CRASH_DUMP:
If the emulator needs to write a crash dump, the value
of this variable will be the file name of the crash dump
file. If the variable is not set, the name of the crash
dump file will be erl_crash.dump in the current direc-
tory.
ERL_CRASH_DUMP_NICE:
Unix systems: If the emulator needs to write a crash
dump, it will use the value of this variable to set the
nice value for the process, thus lowering its priority.
The allowable range is 1 through 39 (higher values will
be replaced with 39). The highest value, 39, will give
the process the lowest priority.
ERL_CRASH_DUMP_SECONDS:
Unix systems: This variable gives the number of seconds
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User Commands erl(1)
that the emulator will be allowed to spend writing a
crash dump. When the given number of seconds have
elapsed, the emulator will be terminated by a SIGALRM
signal.
If the environment variable is not set or it is set to
zero seconds, ERL_CRASH_DUMP_SECONDS=0, the runtime sys-
tem will not even attempt to write the crash dump file.
It will just terminate.
If the environment variable is set to negative valie,
e.g. ERL_CRASH_DUMP_SECONDS=-1, the runtime system will
wait indefinitely for the crash dump file to be written.
This environment variable is used in conjuction with
heart if heart is running:
ERL_CRASH_DUMP_SECONDS=0:
Suppresses the writing a crash dump file entirely,
thus rebooting the runtime system immediately. This is
the same as not setting the environment variable.
ERL_CRASH_DUMP_SECONDS=-1:
Setting the environment variable to a negative value
will cause the termination of the runtime system to
wait until the crash dump file has been completly
written.
ERL_CRASH_DUMP_SECONDS=S:
Will wait for S seconds to complete the crash dump
file and then terminate the runtime system.
ERL_AFLAGS:
The content of this environment variable will be added
to the beginning of the command line for erl.
The -extra flag is treated specially. Its scope ends at
the end of the environment variable content. Arguments
following an -extra flag are moved on the command line
into the -extra section, i.e. the end of the command
line following after an -extra flag.
ERL_ZFLAGS and ERL_FLAGS:
The content of these environment variables will be added
to the end of the command line for erl.
The -extra flag is treated specially. Its scope ends at
the end of the environment variable content. Arguments
following an -extra flag are moved on the command line
into the -extra section, i.e. the end of the command
line following after an -extra flag.
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User Commands erl(1)
ERL_LIBS:
This environment variable contains a list of additional
library directories that the code server will search for
applications and add to the code path. See code(3).
ERL_EPMD_ADDRESS:
This environment variable may be set to a comma-sepa-
rated list of IP addresses, in which case the epmd dae-
mon will listen only on the specified address(es) and on
the loopback address (which is implicitly added to the
list if it has not been specified).
ERL_EPMD_PORT:
This environment variable can contain the port number to
use when communicating with epmd. The default port will
work fine in most cases. A different port can be speci-
fied to allow nodes of independent clusters to co-exist
on the same host. All nodes in a cluster must use the
same epmd port number.
CONFIGURATION
The standard Erlang/OTP system can be re-configured to
change the default behavior on start-up.
The .erlang Start-up File:
When Erlang/OTP is started, the system searches for a
file named .erlang in the directory where Erlang/OTP is
started. If not found, the user's home directory is
searched for an .erlang file.
If an .erlang file is found, it is assumed to contain
valid Erlang expressions. These expressions are evalu-
ated as if they were input to the shell.
A typical .erlang file contains a set of search paths,
for example:
io:format("executing user profile in HOME/.erlang\n",[]).
code:add_path("/home/calvin/test/ebin").
code:add_path("/home/hobbes/bigappl-1.2/ebin").
io:format(".erlang rc finished\n",[]).
user_default and shell_default:
Functions in the shell which are not prefixed by a mod-
ule name are assumed to be functional objects (Funs),
built-in functions (BIFs), or belong to the module
user_default or shell_default.
To include private shell commands, define them in a mod-
ule user_default and add the following argument as the
first line in the .erlang file.
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User Commands erl(1)
code:load_abs("..../user_default").
erl:
If the contents of .erlang are changed and a private
version of user_default is defined, it is possible to
customize the Erlang/OTP environment. More powerful
changes can be made by supplying command line arguments
in the start-up script erl. Refer to erl(1) and init(3)
for further information.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/erlang |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
SEE ALSO
init(3), erl_prim_loader(3), erl_boot_server(3), code(3),
application(3), heart(3), net_kernel(3), auth(3), make(3),
epmd(1), erts_alloc(3)
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.erlang.org/download/otp_src_R15B03-1.tar.gz
Further information about this software can be found on the
open source community website at http://www.erlang.org/.
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