1erl(1) User Commands erl(1)
2
6 erl - The Erlang emulator.
7
9 The erl program starts an Erlang runtime system. The exact details (for
10 example, whether erl is a script or a program and which other programs
11 it calls) are system-dependent.
12 Windows users probably want to use the werl program instead, which runs
14 in its own window with scrollbars and supports command-line editing.
15 The erl program on Windows provides no line editing in its shell, and
16 on Windows 95 there is no way to scroll back to text that has scrolled
17 off the screen. The erl program must be used, however, in pipelines or
18 if you want to redirect standard input or output.
19 Note:
21 As from ERTS 5.9 (Erlang/OTP R15B) the runtime system does by default
22 not bind schedulers to logical processors. For more information, see
23 system flag +sbt.
24
27 erl <arguments>
28 Starts an Erlang runtime system.
30 The arguments can be divided into emulator flags, flags, and
32 plain arguments:
33 * Any argument starting with character + is interpreted as an
35 emulator flag.
36 As indicated by the name, emulator flags control the behav‐
38 ior of the emulator.
39 * Any argument starting with character - (hyphen) is inter‐
41 preted as a flag, which is to be passed to the Erlang part
42 of the runtime system, more specifically to the init system
43 process, see init(3).
44 The init process itself interprets some of these flags, the
46 init flags. It also stores any remaining flags, the user
47 flags. The latter can be retrieved by calling init:get_argu‐
48 ment/1.
49 A small number of "-" flags exist, which now actually are
51 emulator flags, see the description below.
52 * Plain arguments are not interpreted in any way. They are
54 also stored by the init process and can be retrieved by
55 calling init:get_plain_arguments/0. Plain arguments can
56 occur before the first flag, or after a -- flag. Also, the
57 -extra flag causes everything that follows to become plain
58 arguments.
59 Examples:
61 % erl +W w -sname arnie +R 9 -s my_init -extra +bertie
63 (arnie@host)1> init:get_argument(sname).
64 {ok,[["arnie"]]}
65 (arnie@host)2> init:get_plain_arguments().
66 ["+bertie"]
67 Here +W w and +R 9 are emulator flags. -s my_init is an init
69 flag, interpreted by init. -sname arnie is a user flag, stored
70 by init. It is read by Kernel and causes the Erlang runtime sys‐
71 tem to become distributed. Finally, everything after -extra
72 (that is, +bertie) is considered as plain arguments.
73 % erl -myflag 1
75 1> init:get_argument(myflag).
76 {ok,[["1"]]}
77 2> init:get_plain_arguments().
78 []
79 Here the user flag -myflag 1 is passed to and stored by the init
81 process. It is a user-defined flag, presumably used by some
82 user-defined application.
83
85 In the following list, init flags are marked "(init flag)". Unless oth‐
86 erwise specified, all other flags are user flags, for which the values
87 can be retrieved by calling init:get_argument/1. Notice that the list
88 of user flags is not exhaustive, there can be more application-specific
89 flags that instead are described in the corresponding application docu‐
90 mentation.
91 -- (init flag):
93 Everything following -- up to the next flag (-flag or +flag) is
94 considered plain arguments and can be retrieved using
95 init:get_plain_arguments/0.
96 -Application Par Val:
98 Sets the application configuration parameter Par to the value Val
99 for the application Application; see app(4) and application(3).
100 -args_file FileName:
102 Command-line arguments are read from the file FileName. The argu‐
103 ments read from the file replace flag '-args_file FileName' on the
104 resulting command line.
105 The file FileName is to be a plain text file and can contain com‐
107 ments and command-line arguments. A comment begins with a # charac‐
108 ter and continues until the next end of line character. Backslash
109 (\\) is used as quoting character. All command-line arguments
110 accepted by erl are allowed, also flag -args_file FileName. Be
111 careful not to cause circular dependencies between files containing
112 flag -args_file, though.
113 The flag -extra is treated in special way. Its scope ends at the
115 end of the file. Arguments following an -extra flag are moved on
116 the command line into the -extra section, that is, the end of the
117 command line following after an -extra flag.
118 -async_shell_start:
120 The initial Erlang shell does not read user input until the system
121 boot procedure has been completed (Erlang/OTP 5.4 and later). This
122 flag disables the start synchronization feature and lets the shell
123 start in parallel with the rest of the system.
124 -boot File:
126 Specifies the name of the boot file, File.boot, which is used to
127 start the system; see init(3). Unless File contains an absolute
128 path, the system searches for File.boot in the current and
129 $ROOT/bin directories.
130 Defaults to $ROOT/bin/start.boot.
132 -boot_var Var Dir:
134 If the boot script contains a path variable Var other than $ROOT,
135 this variable is expanded to Dir. Used when applications are
136 installed in another directory than $ROOT/lib; see sys‐
137 tools:make_script/1,2 in SASL.
138 -code_path_cache:
140 Enables the code path cache of the code server; see code(3).
141 -compile Mod1 Mod2 ...:
143 Compiles the specified modules and then terminates (with non-zero
144 exit code if the compilation of some file did not succeed). Implies
145 -noinput.
146 Not recommended; use erlc instead.
148 -config Config:
150 Specifies the name of a configuration file, Config.config, which is
151 used to configure applications; see app(4) and application(3).
152 -connect_all false:
154 If this flag is present, global does not maintain a fully connected
155 network of distributed Erlang nodes, and then global name registra‐
156 tion cannot be used; see global(3).
157 -cookie Cookie:
159 Obsolete flag without any effect and common misspelling for -set‐
160 cookie. Use -setcookie instead.
161 -detached:
163 Starts the Erlang runtime system detached from the system console.
164 Useful for running daemons and backgrounds processes. Implies
165 -noinput.
166 -emu_args:
168 Useful for debugging. Prints the arguments sent to the emulator.
169 -emu_type Type:
171 Start an emulator of a different type. For example, to start the
172 lock-counter emualator, use -emu_type lcnt. (The emulator must
173 already be built. Use the configure option --enable-lock-counter to
174 build the lock-counter emulator.)
175 -env Variable Value:
177 Sets the host OS environment variable Variable to the value Value
178 for the Erlang runtime system. Example:
179 % erl -env DISPLAY gin:0
181 In this example, an Erlang runtime system is started with environ‐
183 ment variable DISPLAY set to gin:0.
184 -epmd_module Module (init flag):
186 Configures the module responsible to communicate to epmd. Defaults
187 to erl_epmd.
188 -eval Expr (init flag):
190 Makes init evaluate the expression Expr; see init(3).
191 -extra (init flag):
193 Everything following -extra is considered plain arguments and can
194 be retrieved using init:get_plain_arguments/0.
195 -heart:
197 Starts heartbeat monitoring of the Erlang runtime system; see
198 heart(3).
199 -hidden:
201 Starts the Erlang runtime system as a hidden node, if it is run as
202 a distributed node. Hidden nodes always establish hidden connec‐
203 tions to all other nodes except for nodes in the same global group.
204 Hidden connections are not published on any of the connected nodes,
205 that is, none of the connected nodes are part of the result from
206 nodes/0 on the other node. See also hidden global groups;
207 global_group(3).
208 -hosts Hosts:
210 Specifies the IP addresses for the hosts on which Erlang boot
211 servers are running, see erl_boot_server(3). This flag is mandatory
212 if flag -loader inet is present.
213 The IP addresses must be specified in the standard form (four deci‐
215 mal numbers separated by periods, for example, "150.236.20.74".
216 Hosts names are not acceptable, but a broadcast address (preferably
217 limited to the local network) is.
218 -id Id:
220 Specifies the identity of the Erlang runtime system. If it is run
221 as a distributed node, Id must be identical to the name supplied
222 together with flag -sname or -name.
223 -init_debug:
225 Makes init write some debug information while interpreting the boot
226 script.
227 -instr (emulator flag):
229 Selects an instrumented Erlang runtime system (virtual machine) to
230 run, instead of the ordinary one. When running an instrumented run‐
231 time system, some resource usage data can be obtained and analyzed
232 using the instrument module. Functionally, it behaves exactly like
233 an ordinary Erlang runtime system.
234 -loader Loader:
236 Specifies the method used by erl_prim_loader to load Erlang modules
237 into the system; see erl_prim_loader(3). Two Loader methods are
238 supported:
239 * efile, which means use the local file system, this is the
241 default.
242 * inet, which means use a boot server on another machine. The flags
244 -id, -hosts and -setcookie must also be specified.
245 If Loader is something else, the user-supplied Loader port program
247 is started.
248 -make:
250 Makes the Erlang runtime system invoke make:all() in the current
251 working directory and then terminate; see make(3). Implies -noin‐
252 put.
253 -man Module:
255 Displays the manual page for the Erlang module Module. Only sup‐
256 ported on Unix.
257 -mode interactive | embedded:
259 Modules are auto loaded when they are first referenced if the run‐
260 time system runs in interactive mode, which is the default. In
261 embedded mode modules are not auto loaded. The latter is recom‐
262 mended when the boot script preloads all modules, as conventionally
263 happens in OTP releases. See code(3).
264 -name Name:
266 Makes the Erlang runtime system into a distributed node. This flag
267 invokes all network servers necessary for a node to become distrib‐
268 uted; see net_kernel(3). It is also ensured that epmd runs on the
269 current host before Erlang is started; see epmd(1).and the
270 -start_epmd option.
271 The node name will be Name@Host, where Host is the fully qualified
273 host name of the current host. For short names, use flag -sname
274 instead.
275 Warning:
277 Starting a distributed node without also specifying -proto_dist
278 inet_tls will expose the node to attacks that may give the attacker
279 complete access to the node and in extension the cluster. When using
280 un-secure distributed nodes, make sure that the network is configured
281 to keep potential attackers out.
282 -noinput:
285 Ensures that the Erlang runtime system never tries to read any
286 input. Implies -noshell.
287 -noshell:
289 Starts an Erlang runtime system with no shell. This flag makes it
290 possible to have the Erlang runtime system as a component in a
291 series of Unix pipes.
292 -nostick:
294 Disables the sticky directory facility of the Erlang code server;
295 see code(3).
296 -oldshell:
298 Invokes the old Erlang shell from Erlang/OTP 3.3. The old shell can
299 still be used.
300 -pa Dir1 Dir2 ...:
302 Adds the specified directories to the beginning of the code path,
303 similar to code:add_pathsa/1. Note that the order of the given
304 directories will be reversed in the resulting path.
305 As an alternative to -pa, if several directories are to be
307 prepended to the code path and the directories have a common parent
308 directory, that parent directory can be specified in environment
309 variable ERL_LIBS; see code(3).
310 -pz Dir1 Dir2 ...:
312 Adds the specified directories to the end of the code path, similar
313 to code:add_pathsz/1; see code(3).
314 -path Dir1 Dir2 ...:
316 Replaces the path specified in the boot script; see script(4).
317 -proto_dist Proto:
319 Specifies a protocol for Erlang distribution:
322 inet_tcp:
324 TCP over IPv4 (the default)
325 inet_tls:
327 Distribution over TLS/SSL, See the Using SSL for Erlang Distri‐
328 bution User's Guide for details on how to setup a secure distrib‐
329 uted node.
330 inet6_tcp:
332 TCP over IPv6
333 For example, to start up IPv6 distributed nodes:
335 % erl -name test@ipv6node.example.com -proto_dist inet6_tcp
337 -remsh Node:
339 Starts Erlang with a remote shell connected to Node.
340 -rsh Program:
342 Specifies an alternative to rsh for starting a slave node on a
343 remote host; see slave(3).
344 -run Mod [Func [Arg1, Arg2, ...]] (init flag):
346 Makes init call the specified function. Func defaults to start. If
347 no arguments are provided, the function is assumed to be of arity
348 0. Otherwise it is assumed to be of arity 1, taking the list
349 [Arg1,Arg2,...] as argument. All arguments are passed as strings.
350 See init(3).
351 -s Mod [Func [Arg1, Arg2, ...]] (init flag):
353 Makes init call the specified function. Func defaults to start. If
354 no arguments are provided, the function is assumed to be of arity
355 0. Otherwise it is assumed to be of arity 1, taking the list
356 [Arg1,Arg2,...] as argument. All arguments are passed as atoms. See
357 init(3).
358 -setcookie Cookie:
360 Sets the magic cookie of the node to Cookie; see
361 erlang:set_cookie/2.
362 -shutdown_time Time:
364 Specifies how long time (in milliseconds) the init process is
365 allowed to spend shutting down the system. If Time milliseconds
366 have elapsed, all processes still existing are killed. Defaults to
367 infinity.
368 -sname Name:
370 Makes the Erlang runtime system into a distributed node, similar to
371 -name, but the host name portion of the node name Name@Host will be
372 the short name, not fully qualified.
373 This is sometimes the only way to run distributed Erlang if the
375 Domain Name System (DNS) is not running. No communication can exist
376 between nodes running with flag -sname and those running with flag
377 -name, as node names must be unique in distributed Erlang systems.
378 Warning:
380 Starting a distributed node without also specifying -proto_dist
381 inet_tls will expose the node to attacks that may give the attacker
382 complete access to the node and in extension the cluster. When using
383 un-secure distributed nodes, make sure that the network is configured
384 to keep potential attackers out.
385 -start_epmd true | false:
388 Specifies whether Erlang should start epmd on startup. By default
389 this is true, but if you prefer to start epmd manually, set this to
390 false.
391 This only applies if Erlang is started as a distributed node, i.e.
393 if -name or -sname is specified. Otherwise, epmd is not started
394 even if -start_epmd true is given.
395 Note that a distributed node will fail to start if epmd is not run‐
397 ning.
398 -version (emulator flag):
400 Makes the emulator print its version number. The same as erl +V.
401
403 erl invokes the code for the Erlang emulator (virtual machine), which
404 supports the following flags:
405 +a size:
407 Suggested stack size, in kilowords, for threads in the async thread
408 pool. Valid range is 16-8192 kilowords. The default suggested stack
409 size is 16 kilowords, that is, 64 kilobyte on 32-bit architectures.
410 This small default size has been chosen because the number of async
411 threads can be large. The default size is enough for drivers deliv‐
412 ered with Erlang/OTP, but might not be large enough for other
413 dynamically linked-in drivers that use the driver_async() function‐
414 ality. Notice that the value passed is only a suggestion, and it
415 can even be ignored on some platforms.
416 +A size:
418 Sets the number of threads in async thread pool. Valid range is
419 0-1024. Defaults to 1.
420 +B [c | d | i]:
422 Option c makes Ctrl-C interrupt the current shell instead of invok‐
423 ing the emulator break handler. Option d (same as specifying +B
424 without an extra option) disables the break handler. Option i makes
425 the emulator ignore any break signal.
426 If option c is used with oldshell on Unix, Ctrl-C will restart the
428 shell process rather than interrupt it.
429 Notice that on Windows, this flag is only applicable for werl, not
431 erl (oldshell). Notice also that Ctrl-Break is used instead of
432 Ctrl-C on Windows.
433 +c true | false:
435 Enables or disables time correction:
436 true:
438 Enables time correction. This is the default if time correction
439 is supported on the specific platform.
440 false:
442 Disables time correction.
443 For backward compatibility, the boolean value can be omitted. This
445 is interpreted as +c false.
446 +C no_time_warp | single_time_warp | multi_time_warp:
448 Sets time warp mode:
449 no_time_warp:
451 No time warp mode (the default)
452 single_time_warp:
454 Single time warp mode
455 multi_time_warp:
457 Multi-time warp mode
458 +d:
460 If the emulator detects an internal error (or runs out of memory),
461 it, by default, generates both a crash dump and a core dump. The
462 core dump is, however, not very useful as the content of process
463 heaps is destroyed by the crash dump generation.
464 Option +d instructs the emulator to produce only a core dump and no
466 crash dump if an internal error is detected.
467 Calling erlang:halt/1 with a string argument still produces a crash
469 dump. On Unix systems, sending an emulator process a SIGUSR1 signal
470 also forces a crash dump.
471 +e Number:
473 Sets the maximum number of ETS tables. This limit is partially
474 obsolete.
475 +ec:
477 Forces option compressed on all ETS tables. Only intended for test
478 and evaluation.
479 +fnl:
481 The virtual machine works with filenames as if they are encoded
482 using the ISO Latin-1 encoding, disallowing Unicode characters with
483 code points > 255.
484 For more information about Unicode filenames, see section Unicode
486 Filenames in the STDLIB User's Guide. Notice that this value also
487 applies to command-line parameters and environment variables (see
488 section Unicode in Environment and Parameters in the STDLIB User's
489 Guide).
490 +fnu[{w|i|e}]:
492 The virtual machine works with filenames as if they are encoded
493 using UTF-8 (or some other system-specific Unicode encoding). This
494 is the default on operating systems that enforce Unicode encoding,
495 that is, Windows and MacOS X.
496 The +fnu switch can be followed by w, i, or e to control how
498 wrongly encoded filenames are to be reported:
499 * w means that a warning is sent to the error_logger whenever a
501 wrongly encoded filename is "skipped" in directory listings. This
502 is the default.
503 * i means that those wrongly encoded filenames are silently
505 ignored.
506 * e means that the API function returns an error whenever a wrongly
508 encoded filename (or directory name) is encountered.
509 Notice that file:read_link/1 always returns an error if the link
511 points to an invalid filename.
512 For more information about Unicode filenames, see section Unicode
514 Filenames in the STDLIB User's Guide. Notice that this value also
515 applies to command-line parameters and environment variables (see
516 section Unicode in Environment and Parameters in the STDLIB User's
517 Guide).
518 +fna[{w|i|e}]:
520 Selection between +fnl and +fnu is done based on the current locale
521 settings in the OS. This means that if you have set your terminal
522 for UTF-8 encoding, the filesystem is expected to use the same
523 encoding for filenames. This is default on all operating systems,
524 except MacOS X and Windows.
525 The +fna switch can be followed by w, i, or e. This has effect if
527 the locale settings cause the behavior of +fnu to be selected; see
528 the description of +fnu above. If the locale settings cause the
529 behavior of +fnl to be selected, then w, i, or e have no effect.
530 For more information about Unicode filenames, see section Unicode
532 Filenames in the STDLIB User's Guide. Notice that this value also
533 applies to command-line parameters and environment variables (see
534 section Unicode in Environment and Parameters in the STDLIB User's
535 Guide).
536 +hms Size:
538 Sets the default heap size of processes to the size Size.
539 +hmbs Size:
541 Sets the default binary virtual heap size of processes to the size
542 Size.
543 +hmax Size:
545 Sets the default maximum heap size of processes to the size Size.
546 Defaults to 0, which means that no maximum heap size is used. For
547 more information, see process_flag(max_heap_size, MaxHeapSize).
548 +hmaxel true|false:
550 Sets whether to send an error logger message or not for processes
551 reaching the maximum heap size. Defaults to true. For more informa‐
552 tion, see process_flag(max_heap_size, MaxHeapSize).
553 +hmaxk true|false:
555 Sets whether to kill processes reaching the maximum heap size or
556 not. Default to true. For more information, see
557 process_flag(max_heap_size, MaxHeapSize).
558 +hpds Size:
560 Sets the initial process dictionary size of processes to the size
561 Size.
562 +hmqd off_heap|on_heap:
564 Sets the default value for process flag message_queue_data.
565 Defaults to on_heap. If +hmqd is not passed, on_heap will be the
566 default. For more information, see process_flag(message_queue_data,
567 MQD).
568 +IOp PollSets:
570 Sets the number of IO pollsets to use when polling for I/O. This
571 option is only used on platforms that support concurrent updates of
572 a pollset, otherwise the same number of pollsets are used as IO
573 poll threads. The default is 1.
574 +IOt PollThreads:
576 Sets the number of IO poll threads to use when polling for I/O. The
577 maximum number of poll threads allowed is 1024. The default is 1.
578 A good way to check if more IO poll threads are needed is to use
580 microstate accounting and see what the load of the IO poll thread
581 is. If it is high it could be a good idea to add more threads.
582 +IOPp PollSetsPercentage:
584 Similar to +IOp but uses percentages to set the number of IO
585 pollsets to create, based on the number of poll threads configured.
586 If both +IOPp and +IOp are used, +IOPp is ignored.
587 +IOPt PollThreadsPercentage:
589 Similar to +IOt but uses percentages to set the number of IO poll
590 threads to create, based on the number of schedulers configured. If
591 both +IOPt and +IOt are used, +IOPt is ignored.
592 +l:
594 Enables autoload tracing, displaying information while loading
595 code.
596 +L:
598 Prevents loading information about source filenames and line num‐
599 bers. This saves some memory, but exceptions do not contain infor‐
600 mation about the filenames and line numbers.
601 +MFlag Value:
603 Memory allocator-specific flags. For more information, see
604 erts_alloc(3).
605 +pc Range:
607 Sets the range of characters that the system considers printable in
608 heuristic detection of strings. This typically affects the shell,
609 debugger, and io:format functions (when ~tp is used in the format
610 string).
611 Two values are supported for Range:
613 latin1:
615 The default. Only characters in the ISO Latin-1 range can be con‐
616 sidered printable. This means that a character with a code point
617 > 255 is never considered printable and that lists containing
618 such characters are displayed as lists of integers rather than
619 text strings by tools.
620 unicode:
622 All printable Unicode characters are considered when determining
623 if a list of integers is to be displayed in string syntax. This
624 can give unexpected results if, for example, your font does not
625 cover all Unicode characters.
626 See also io:printable_range/0 in STDLIB.
628 +P Number:
630 Sets the maximum number of simultaneously existing processes for
631 this system if a Number is passed as value. Valid range for Number
632 is [1024-134217727]
633 NOTE: The actual maximum chosen may be much larger than the Number
635 passed. Currently the runtime system often, but not always, chooses
636 a value that is a power of 2. This might, however, be changed in
637 the future. The actual value chosen can be checked by calling
638 erlang:system_info(process_limit).
639 The default value is 262144
641 +Q Number:
643 Sets the maximum number of simultaneously existing ports for this
644 system if a Number is passed as value. Valid range for Number is
645 [1024-134217727]
646 NOTE: The actual maximum chosen may be much larger than the actual
648 Number passed. Currently the runtime system often, but not always,
649 chooses a value that is a power of 2. This might, however, be
650 changed in the future. The actual value chosen can be checked by
651 calling erlang:system_info(port_limit).
652 The default value used is normally 65536. However, if the runtime
654 system is able to determine maximum amount of file descriptors that
655 it is allowed to open and this value is larger than 65536, the cho‐
656 sen value will increased to a value larger or equal to the maximum
657 amount of file descriptors that can be opened.
658 On Windows the default value is set to 8196 because the normal OS
660 limitations are set higher than most machines can handle.
661 +R ReleaseNumber:
663 Sets the compatibility mode.
664 The distribution mechanism is not backward compatible by default.
666 This flag sets the emulator in compatibility mode with an earlier
667 Erlang/OTP release ReleaseNumber. The release number must be in the
668 range <current release>-2..<current release>. This limits the emu‐
669 lator, making it possible for it to communicate with Erlang nodes
670 (as well as C- and Java nodes) running that earlier release.
671 Note:
673 Ensure that all nodes (Erlang-, C-, and Java nodes) of a distributed
674 Erlang system is of the same Erlang/OTP release, or from two differ‐
675 ent Erlang/OTP releases X and Y, where all Y nodes have compatibility
676 mode X.
677 +r:
680 Forces ETS memory block to be moved on realloc.
681 +rg ReaderGroupsLimit:
683 Limits the number of reader groups used by read/write locks opti‐
684 mized for read operations in the Erlang runtime system. By default
685 the reader groups limit is 64.
686 When the number of schedulers is less than or equal to the reader
688 groups limit, each scheduler has its own reader group. When the
689 number of schedulers is larger than the reader groups limit, sched‐
690 ulers share reader groups. Shared reader groups degrade read lock
691 and read unlock performance while many reader groups degrade write
692 lock performance. So, the limit is a tradeoff between performance
693 for read operations and performance for write operations. Each
694 reader group consumes 64 byte in each read/write lock.
695 Notice that a runtime system using shared reader groups benefits
697 from binding schedulers to logical processors, as the reader groups
698 are distributed better between schedulers.
699 +S Schedulers:SchedulerOnline:
701 Sets the number of scheduler threads to create and scheduler
702 threads to set online. The maximum for both values is 1024. If the
703 Erlang runtime system is able to determine the number of logical
704 processors configured and logical processors available, Schedulers
705 defaults to logical processors configured, and SchedulersOnline
706 defaults to logical processors available; otherwise the default
707 values are 1. Schedulers can be omitted if :SchedulerOnline is not
708 and conversely. The number of schedulers online can be changed at
709 runtime through erlang:system_flag(schedulers_online, SchedulersOn‐
710 line).
711 If Schedulers or SchedulersOnline is specified as a negative num‐
713 ber, the value is subtracted from the default number of logical
714 processors configured or logical processors available, respec‐
715 tively.
716 Specifying value 0 for Schedulers or SchedulersOnline resets the
718 number of scheduler threads or scheduler threads online, respec‐
719 tively, to its default value.
720 +SP SchedulersPercentage:SchedulersOnlinePercentage:
722 Similar to +S but uses percentages to set the number of scheduler
723 threads to create, based on logical processors configured, and
724 scheduler threads to set online, based on logical processors avail‐
725 able. Specified values must be > 0. For example, +SP 50:25 sets the
726 number of scheduler threads to 50% of the logical processors con‐
727 figured, and the number of scheduler threads online to 25% of the
728 logical processors available. SchedulersPercentage can be omitted
729 if :SchedulersOnlinePercentage is not and conversely. The number of
730 schedulers online can be changed at runtime through erlang:sys‐
731 tem_flag(schedulers_online, SchedulersOnline).
732 This option interacts with +S settings. For example, on a system
734 with 8 logical cores configured and 8 logical cores available, the
735 combination of the options +S 4:4 +SP 50:25 (in either order)
736 results in 2 scheduler threads (50% of 4) and 1 scheduler thread
737 online (25% of 4).
738 +SDcpu DirtyCPUSchedulers:DirtyCPUSchedulersOnline:
740 Sets the number of dirty CPU scheduler threads to create and dirty
741 CPU scheduler threads to set online. The maximum for both values is
742 1024, and each value is further limited by the settings for normal
743 schedulers:
744 * The number of dirty CPU scheduler threads created cannot exceed
746 the number of normal scheduler threads created.
747 * The number of dirty CPU scheduler threads online cannot exceed
749 the number of normal scheduler threads online.
750 For details, see the +S and +SP. By default, the number of dirty
752 CPU scheduler threads created equals the number of normal scheduler
753 threads created, and the number of dirty CPU scheduler threads
754 online equals the number of normal scheduler threads online. Dirty‐
755 CPUSchedulers can be omitted if :DirtyCPUSchedulersOnline is not
756 and conversely. The number of dirty CPU schedulers online can be
757 changed at runtime through erlang:system_flag(dirty_cpu_sched‐
758 ulers_online, DirtyCPUSchedulersOnline).
759 The amount of dirty CPU schedulers is limited by the amount of nor‐
761 mal schedulers in order to limit the effect on processes executing
762 on ordinary schedulers. If the amount of dirty CPU schedulers was
763 allowed to be unlimited, dirty CPU bound jobs would potentially
764 starve normal jobs.
765 +SDPcpu DirtyCPUSchedulersPercentage:DirtyCPUSchedulersOnlinePercent‐
767 age:
768 Similar to +SDcpu but uses percentages to set the number of dirty
769 CPU scheduler threads to create and the number of dirty CPU sched‐
770 uler threads to set online. Specified values must be > 0. For exam‐
771 ple, +SDPcpu 50:25 sets the number of dirty CPU scheduler threads
772 to 50% of the logical processors configured and the number of dirty
773 CPU scheduler threads online to 25% of the logical processors
774 available. DirtyCPUSchedulersPercentage can be omitted if :DirtyC‐
775 PUSchedulersOnlinePercentage is not and conversely. The number of
776 dirty CPU schedulers online can be changed at runtime through
777 erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUScheduler‐
778 sOnline).
779 This option interacts with +SDcpu settings. For example, on a sys‐
781 tem with 8 logical cores configured and 8 logical cores available,
782 the combination of the options +SDcpu 4:4 +SDPcpu 50:25 (in either
783 order) results in 2 dirty CPU scheduler threads (50% of 4) and 1
784 dirty CPU scheduler thread online (25% of 4).
785 +SDio DirtyIOSchedulers:
787 Sets the number of dirty I/O scheduler threads to create. Valid
788 range is 0-1024. By default, the number of dirty I/O scheduler
789 threads created is 10, same as the default number of threads in the
790 async thread pool.
791 The amount of dirty IO schedulers is not limited by the amount of
793 normal schedulers like the amount of dirty CPU schedulers. This
794 since only I/O bound work is expected to execute on dirty I/O
795 schedulers. If the user should schedule CPU bound jobs on dirty I/O
796 schedulers, these jobs might starve ordinary jobs executing on
797 ordinary schedulers.
798 +sFlag Value:
800 Scheduling specific flags.
801 +sbt BindType:
803 Sets scheduler bind type.
804 Schedulers can also be bound using flag +stbt. The only differ‐
806 ence between these two flags is how the following errors are han‐
807 dled:
808 * Binding of schedulers is not supported on the specific plat‐
810 form.
811 * No available CPU topology. That is, the runtime system was not
813 able to detect the CPU topology automatically, and no user-
814 defined CPU topology was set.
815 If any of these errors occur when +sbt has been passed, the run‐
817 time system prints an error message, and refuses to start. If any
818 of these errors occur when +stbt has been passed, the runtime
819 system silently ignores the error, and start up using unbound
820 schedulers.
821 Valid BindTypes:
823 u:
825 unbound - Schedulers are not bound to logical processors, that
826 is, the operating system decides where the scheduler threads
827 execute, and when to migrate them. This is the default.
828 ns:
830 no_spread - Schedulers with close scheduler identifiers are
831 bound as close as possible in hardware.
832 ts:
834 thread_spread - Thread refers to hardware threads (such as
835 Intel's hyper-threads). Schedulers with low scheduler identi‐
836 fiers, are bound to the first hardware thread of each core,
837 then schedulers with higher scheduler identifiers are bound to
838 the second hardware thread of each core,and so on.
839 ps:
841 processor_spread - Schedulers are spread like thread_spread,
842 but also over physical processor chips.
843 s:
845 spread - Schedulers are spread as much as possible.
846 nnts:
848 no_node_thread_spread - Like thread_spread, but if multiple
849 Non-Uniform Memory Access (NUMA) nodes exist, schedulers are
850 spread over one NUMA node at a time, that is, all logical pro‐
851 cessors of one NUMA node are bound to schedulers in sequence.
852 nnps:
854 no_node_processor_spread - Like processor_spread, but if multi‐
855 ple NUMA nodes exist, schedulers are spread over one NUMA node
856 at a time, that is, all logical processors of one NUMA node are
857 bound to schedulers in sequence.
858 tnnps:
860 thread_no_node_processor_spread - A combination of
861 thread_spread, and no_node_processor_spread. Schedulers are
862 spread over hardware threads across NUMA nodes, but schedulers
863 are only spread over processors internally in one NUMA node at
864 a time.
865 db:
867 default_bind - Binds schedulers the default way. Defaults to
868 thread_no_node_processor_spread (which can change in the
869 future).
870 Binding of schedulers is only supported on newer Linux, Solaris,
872 FreeBSD, and Windows systems.
873 If no CPU topology is available when flag +sbt is processed and
875 BindType is any other type than u, the runtime system fails to
876 start. CPU topology can be defined using flag +sct. Notice that
877 flag +sct can have to be passed before flag +sbt on the command
878 line (if no CPU topology has been automatically detected).
879 The runtime system does by default not bind schedulers to logical
881 processors.
882 Note:
884 If the Erlang runtime system is the only operating system process
885 that binds threads to logical processors, this improves the perfor‐
886 mance of the runtime system. However, if other operating system
887 processes (for example another Erlang runtime system) also bind
888 threads to logical processors, there can be a performance penalty
889 instead. This performance penalty can sometimes be severe. If so,
890 you are advised not to bind the schedulers.
891 How schedulers are bound matters. For example, in situations when
894 there are fewer running processes than schedulers online, the
895 runtime system tries to migrate processes to schedulers with low
896 scheduler identifiers. The more the schedulers are spread over
897 the hardware, the more resources are available to the runtime
898 system in such situations.
899 Note:
901 If a scheduler fails to bind, this is often silently ignored, as it
902 is not always possible to verify valid logical processor identi‐
903 fiers. If an error is reported, it is reported to the error_logger.
904 If you want to verify that the schedulers have bound as requested,
905 call erlang:system_info(scheduler_bindings).
906 +sbwt none|very_short|short|medium|long|very_long:
909 Sets scheduler busy wait threshold. Defaults to medium. The
910 threshold determines how long schedulers are to busy wait when
911 running out of work before going to sleep.
912 Note:
914 This flag can be removed or changed at any time without prior
915 notice.
916 +sbwtdcpu none|very_short|short|medium|long|very_long:
919 As +sbwt but affects dirty CPU schedulers. Defaults to short.
920 Note:
922 This flag can be removed or changed at any time without prior
923 notice.
924 +sbwtdio none|very_short|short|medium|long|very_long:
927 As +sbwt but affects dirty IO schedulers. Defaults to short.
928 Note:
930 This flag can be removed or changed at any time without prior
931 notice.
932 +scl true|false:
935 Enables or disables scheduler compaction of load. By default
936 scheduler compaction of load is enabled. When enabled, load bal‐
937 ancing strives for a load distribution, which causes as many
938 scheduler threads as possible to be fully loaded (that is, not
939 run out of work). This is accomplished by migrating load (for
940 example, runnable processes) into a smaller set of schedulers
941 when schedulers frequently run out of work. When disabled, the
942 frequency with which schedulers run out of work is not taken into
943 account by the load balancing logic.
944 +scl false is similar to +sub true, but +sub true also balances
946 scheduler utilization between schedulers.
947 +sct CpuTopology:
949 * <Id> = integer(); when 0 =< <Id> =< 65535
952 * <IdRange> = <Id>-<Id>
954 * <IdOrIdRange> = <Id> | <IdRange>
956 * <IdList> = <IdOrIdRange>,<IdOrIdRange> | <IdOrIdRange>
958 * <LogicalIds> = L<IdList>
960 * <ThreadIds> = T<IdList> | t<IdList>
962 * <CoreIds> = C<IdList> | c<IdList>
964 * <ProcessorIds> = P<IdList> | p<IdList>
966 * <NodeIds> = N<IdList> | n<IdList>
968 * <IdDefs> = <LogicalIds><ThreadIds><CoreIds><Proces‐
970 sorIds><NodeIds> | <LogicalIds><ThreadIds><Cor‐
971 eIds><NodeIds><ProcessorIds>
972 * CpuTopology = <IdDefs>:<IdDefs> | <IdDefs>
974 Sets a user-defined CPU topology. The user-defined CPU topology
976 overrides any automatically detected CPU topology. The CPU topol‐
977 ogy is used when binding schedulers to logical processors.
978 Uppercase letters signify real identifiers and lowercase letters
980 signify fake identifiers only used for description of the topol‐
981 ogy. Identifiers passed as real identifiers can be used by the
982 runtime system when trying to access specific hardware; if they
983 are incorrect the behavior is undefined. Faked logical CPU iden‐
984 tifiers are not accepted, as there is no point in defining the
985 CPU topology without real logical CPU identifiers. Thread, core,
986 processor, and node identifiers can be omitted. If omitted, the
987 thread ID defaults to t0, the core ID defaults to c0, the proces‐
988 sor ID defaults to p0, and the node ID is left undefined. Either
989 each logical processor must belong to only one NUMA node, or no
990 logical processors must belong to any NUMA nodes.
991 Both increasing and decreasing <IdRange>s are allowed.
993 NUMA node identifiers are system wide. That is, each NUMA node on
995 the system must have a unique identifier. Processor identifiers
996 are also system wide. Core identifiers are processor wide. Thread
997 identifiers are core wide.
998 The order of the identifier types implies the hierarchy of the
1000 CPU topology. The valid orders are as follows:
1001 * <LogicalIds><ThreadIds><CoreIds><ProcessorIds><NodeIds>, that
1003 is, thread is part of a core that is part of a processor, which
1004 is part of a NUMA node.
1005 * <LogicalIds><ThreadIds><CoreIds><NodeIds><ProcessorIds>, that
1007 is, thread is part of a core that is part of a NUMA node, which
1008 is part of a processor.
1009 A CPU topology can consist of both processor external, and pro‐
1011 cessor internal NUMA nodes as long as each logical processor
1012 belongs to only one NUMA node. If <ProcessorIds> is omitted, its
1013 default position is before <NodeIds>. That is, the default is
1014 processor external NUMA nodes.
1015 If a list of identifiers is used in an <IdDefs>:
1017 * <LogicalIds> must be a list of identifiers.
1019 * At least one other identifier type besides <LogicalIds> must
1021 also have a list of identifiers.
1022 * All lists of identifiers must produce the same number of iden‐
1024 tifiers.
1025 A simple example. A single quad core processor can be described
1027 as follows:
1028 % erl +sct L0-3c0-3
1030 1> erlang:system_info(cpu_topology).
1031 [{processor,[{core,{logical,0}},
1032 {core,{logical,1}},
1033 {core,{logical,2}},
1034 {core,{logical,3}}]}]
1035 A more complicated example with two quad core processors, each
1037 processor in its own NUMA node. The ordering of logical proces‐
1038 sors is a bit weird. This to give a better example of identifier
1039 lists:
1040 % erl +sct L0-1,3-2c0-3p0N0:L7,4,6-5c0-3p1N1
1042 1> erlang:system_info(cpu_topology).
1043 [{node,[{processor,[{core,{logical,0}},
1044 {core,{logical,1}},
1045 {core,{logical,3}},
1046 {core,{logical,2}}]}]},
1047 {node,[{processor,[{core,{logical,7}},
1048 {core,{logical,4}},
1049 {core,{logical,6}},
1050 {core,{logical,5}}]}]}]
1051 As long as real identifiers are correct, it is OK to pass a CPU
1053 topology that is not a correct description of the CPU topology.
1054 When used with care this can be very useful. This to trick the
1055 emulator to bind its schedulers as you want. For example, if you
1056 want to run multiple Erlang runtime systems on the same machine,
1057 you want to reduce the number of schedulers used and manipulate
1058 the CPU topology so that they bind to different logical CPUs. An
1059 example, with two Erlang runtime systems on a quad core machine:
1060 % erl +sct L0-3c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname one
1062 % erl +sct L3-0c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname two
1063 In this example, each runtime system have two schedulers each
1065 online, and all schedulers online will run on different cores. If
1066 we change to one scheduler online on one runtime system, and
1067 three schedulers online on the other, all schedulers online will
1068 still run on different cores.
1069 Notice that a faked CPU topology that does not reflect how the
1071 real CPU topology looks like is likely to decrease the perfor‐
1072 mance of the runtime system.
1073 For more information, see erlang:system_info(cpu_topology).
1075 +sfwi Interval:
1077 Sets scheduler-forced wakeup interval. All run queues are scanned
1078 each Interval milliseconds. While there are sleeping schedulers
1079 in the system, one scheduler is woken for each non-empty run
1080 queue found. Interval default to 0, meaning this feature is dis‐
1081 abled.
1082 Note:
1084 This feature has been introduced as a temporary workaround for
1085 long-executing native code, and native code that does not bump
1086 reductions properly in OTP. When these bugs have be fixed, this
1087 flag will be removed.
1088 +spp Bool:
1091 Sets default scheduler hint for port parallelism. If set to true,
1092 the virtual machine schedules port tasks when it improves paral‐
1093 lelism in the system. If set to false, the virtual machine tries
1094 to perform port tasks immediately, improving latency at the
1095 expense of parallelism. Default to false. The default used can be
1096 inspected in runtime by calling erlang:system_info(port_parallel‐
1097 ism). The default can be overridden on port creation by passing
1098 option parallelism to erlang:open_port/2.
1099 +sss size:
1101 Suggested stack size, in kilowords, for scheduler threads. Valid
1102 range is 20-8192 kilowords. The default suggested stack size is
1103 128 kilowords.
1104 +sssdcpu size:
1106 Suggested stack size, in kilowords, for dirty CPU scheduler
1107 threads. Valid range is 20-8192 kilowords. The default suggested
1108 stack size is 40 kilowords.
1109 +sssdio size:
1111 Suggested stack size, in kilowords, for dirty IO scheduler
1112 threads. Valid range is 20-8192 kilowords. The default suggested
1113 stack size is 40 kilowords.
1114 +stbt BindType:
1116 Tries to set the scheduler bind type. The same as flag +sbt
1117 except how some errors are handled. For more information, see
1118 +sbt.
1119 +sub true|false:
1121 Enables or disables scheduler utilization balancing of load. By
1122 default scheduler utilization balancing is disabled and instead
1123 scheduler compaction of load is enabled, which strives for a load
1124 distribution that causes as many scheduler threads as possible to
1125 be fully loaded (that is, not run out of work). When scheduler
1126 utilization balancing is enabled, the system instead tries to
1127 balance scheduler utilization between schedulers. That is, strive
1128 for equal scheduler utilization on all schedulers.
1129 +sub true is only supported on systems where the runtime system
1131 detects and uses a monotonically increasing high-resolution
1132 clock. On other systems, the runtime system fails to start.
1133 +sub true implies +scl false. The difference between +sub true
1135 and +scl false is that +scl false does not try to balance the
1136 scheduler utilization.
1137 +swct very_eager|eager|medium|lazy|very_lazy:
1139 Sets scheduler wake cleanup threshold. Defaults to medium. Con‐
1140 trols how eager schedulers are to be requesting wakeup because of
1141 certain cleanup operations. When a lazy setting is used, more
1142 outstanding cleanup operations can be left undone while a sched‐
1143 uler is idling. When an eager setting is used, schedulers are
1144 more frequently woken, potentially increasing CPU-utilization.
1145 Note:
1147 This flag can be removed or changed at any time without prior
1148 notice.
1149 +sws default|legacy:
1152 Sets scheduler wakeup strategy. Default strategy changed in ERTS
1153 5.10 (Erlang/OTP R16A). This strategy was known as proposal in
1154 Erlang/OTP R15. The legacy strategy was used as default from R13
1155 up to and including R15.
1156 Note:
1158 This flag can be removed or changed at any time without prior
1159 notice.
1160 +swt very_low|low|medium|high|very_high:
1163 Sets scheduler wakeup threshold. Defaults to medium. The thresh‐
1164 old determines when to wake up sleeping schedulers when more work
1165 than can be handled by currently awake schedulers exists. A low
1166 threshold causes earlier wakeups, and a high threshold causes
1167 later wakeups. Early wakeups distribute work over multiple sched‐
1168 ulers faster, but work does more easily bounce between sched‐
1169 ulers.
1170 Note:
1172 This flag can be removed or changed at any time without prior
1173 notice.
1174 +swtdcpu very_low|low|medium|high|very_high:
1177 As +swt but affects dirty CPU schedulers. Defaults to medium.
1178 Note:
1180 This flag can be removed or changed at any time without prior
1181 notice.
1182 +swtdio very_low|low|medium|high|very_high:
1185 As +swt but affects dirty IO schedulers. Defaults to medium.
1186 Note:
1188 This flag can be removed or changed at any time without prior
1189 notice.
1190 +t size:
1193 Sets the maximum number of atoms the virtual machine can handle.
1194 Defaults to 1,048,576.
1195 +T Level:
1197 Enables modified timing and sets the modified timing level. Valid
1198 range is 0-9. The timing of the runtime system is changed. A high
1199 level usually means a greater change than a low level. Changing the
1200 timing can be very useful for finding timing-related bugs.
1201 Modified timing affects the following:
1203 Process spawning:
1205 A process calling spawn, spawn_link, spawn_monitor, or spawn_opt
1206 is scheduled out immediately after completing the call. When
1207 higher modified timing levels are used, the caller also sleeps
1208 for a while after it is scheduled out.
1209 Context reductions:
1211 The number of reductions a process is allowed to use before it is
1212 scheduled out is increased or reduced.
1213 Input reductions:
1215 The number of reductions performed before checking I/O is
1216 increased or reduced.
1217 Note:
1219 Performance suffers when modified timing is enabled. This flag is
1220 only intended for testing and debugging.
1221 return_to and return_from trace messages are lost when tracing on the
1223 spawn BIFs.
1224 This flag can be removed or changed at any time without prior notice.
1226 +v:
1229 Verbose.
1230 +V:
1232 Makes the emulator print its version number.
1233 +W w | i | e:
1235 Sets the mapping of warning messages for error_logger. Messages
1236 sent to the error logger using one of the warning routines can be
1237 mapped to errors (+W e), warnings (+W w), or information reports
1238 (+W i). Defaults to warnings. The current mapping can be retrieved
1239 using error_logger:warning_map/0. For more information, see
1240 error_logger:warning_map/0 in Kernel.
1241 +zFlag Value:
1243 Miscellaneous flags:
1244 +zdbbl size:
1246 Sets the distribution buffer busy limit (dist_buf_busy_limit) in
1247 kilobytes. Valid range is 1-2097151. Defaults to 1024.
1248 A larger buffer limit allows processes to buffer more outgoing
1250 messages over the distribution. When the buffer limit has been
1251 reached, sending processes will be suspended until the buffer
1252 size has shrunk. The buffer limit is per distribution channel. A
1253 higher limit gives lower latency and higher throughput at the
1254 expense of higher memory use.
1255 +zdntgc time:
1257 Sets the delayed node table garbage collection time
1258 (delayed_node_table_gc) in seconds. Valid values are either
1259 infinity or an integer in the range 0-100000000. Defaults to 60.
1260 Node table entries that are not referred linger in the table for
1262 at least the amount of time that this parameter determines. The
1263 lingering prevents repeated deletions and insertions in the
1264 tables from occurring.
1265 +ztma true | false:
1267 Enables or disables support for tuple module apply in the emula‐
1268 tor. This is a transitional flag for running code that uses
1269 parameterized modules and was compiled under OTP 20 or earlier.
1270 For future compatibility, the modules will need to be recompiled
1271 with the +tuple_calls compiler option. Defaults to false.
1272
1274 ERL_CRASH_DUMP:
1275 If the emulator needs to write a crash dump, the value of this
1276 variable is the filename of the crash dump file. If the variable is
1277 not set, the name of the crash dump file is erl_crash.dump in the
1278 current directory.
1279 ERL_CRASH_DUMP_NICE:
1281 Unix systems: If the emulator needs to write a crash dump, it uses
1282 the value of this variable to set the nice value for the process,
1283 thus lowering its priority. Valid range is 1-39 (higher values are
1284 replaced with 39). The highest value, 39, gives the process the
1285 lowest priority.
1286 ERL_CRASH_DUMP_SECONDS:
1288 Unix systems: This variable gives the number of seconds that the
1289 emulator is allowed to spend writing a crash dump. When the given
1290 number of seconds have elapsed, the emulator is terminated.
1291 ERL_CRASH_DUMP_SECONDS=0:
1293 If the variable is set to 0 seconds, the runtime system does not
1294 even attempt to write the crash dump file. It only terminates.
1295 This is the default if option -heart is passed to erl and
1296 ERL_CRASH_DUMP_SECONDS is not set.
1297 ERL_CRASH_DUMP_SECONDS=S:
1299 If the variable is set to a positive value S, wait for S seconds
1300 to complete the crash dump file and then terminates the runtime
1301 system with a SIGALRM signal.
1302 ERL_CRASH_DUMP_SECONDS=-1:
1304 A negative value causes the termination of the runtime system to
1305 wait indefinitely until the crash dump file has been completly
1306 written. This is the default if option -heart is not passed to
1307 erl and ERL_CRASH_DUMP_SECONDS is not set.
1308 See also heart(3).
1310 ERL_CRASH_DUMP_BYTES:
1312 This variable sets the maximum size of a crash dump file in bytes.
1313 The crash dump will be truncated if this limit is exceeded. If the
1314 variable is not set, no size limit is enforced by default. If the
1315 variable is set to 0, the runtime system does not even attempt to
1316 write a crash dump file.
1317 Introduced in ERTS 8.1.2 (Erlang/OTP 19.2).
1319 ERL_AFLAGS:
1321 The content of this variable is added to the beginning of the com‐
1322 mand line for erl.
1323 Flag -extra is treated in a special way. Its scope ends at the end
1325 of the environment variable content. Arguments following an -extra
1326 flag are moved on the command line into section -extra, that is,
1327 the end of the command line following an -extra flag.
1328 ERL_ZFLAGS and ERL_FLAGS:
1330 The content of these variables are added to the end of the command
1331 line for erl.
1332 Flag -extra is treated in a special way. Its scope ends at the end
1334 of the environment variable content. Arguments following an -extra
1335 flag are moved on the command line into section -extra, that is,
1336 the end of the command line following an -extra flag.
1337 ERL_LIBS:
1339 Contains a list of additional library directories that the code
1340 server searches for applications and adds to the code path; see
1341 code(3).
1342 ERL_EPMD_ADDRESS:
1344 Can be set to a comma-separated list of IP addresses, in which case
1345 the epmd daemon listens only on the specified address(es) and on
1346 the loopback address (which is implicitly added to the list if it
1347 has not been specified).
1348 ERL_EPMD_PORT:
1350 Can contain the port number to use when communicating with epmd.
1351 The default port works fine in most cases. A different port can be
1352 specified to allow nodes of independent clusters to co-exist on the
1353 same host. All nodes in a cluster must use the same epmd port num‐
1354 ber.
1355
1357 On Unix systems, the Erlang runtime will interpret two types of sig‐
1358 nals.
1359 SIGUSR1:
1361 A SIGUSR1 signal forces a crash dump.
1362 SIGTERM:
1364 A SIGTERM will produce a stop message to the init process. This is
1365 equivalent to a init:stop/0 call.
1366 Introduced in ERTS 8.3 (Erlang/OTP 19.3)
1368 The signal SIGUSR2 is reserved for internal usage. No other signals are
1370 handled.
1371
1373 The standard Erlang/OTP system can be reconfigured to change the
1374 default behavior on startup.
1375 The .erlang startup file:
1377 When Erlang/OTP is started, the system searches for a file named
1378 .erlang in the user's home directory.
1379 If an .erlang file is found, it is assumed to contain valid Erlang
1381 expressions. These expressions are evaluated as if they were input
1382 to the shell.
1383 A typical .erlang file contains a set of search paths, for example:
1385 io:format("executing user profile in HOME/.erlang\n",[]).
1387 code:add_path("/home/calvin/test/ebin").
1388 code:add_path("/home/hobbes/bigappl-1.2/ebin").
1389 io:format(".erlang rc finished\n",[]).
1390 user_default and shell_default:
1392 Functions in the shell that are not prefixed by a module name are
1393 assumed to be functional objects (funs), built-in functions (BIFs),
1394 or belong to the module user_default or shell_default.
1395 To include private shell commands, define them in a module
1397 user_default and add the following argument as the first line in
1398 the .erlang file:
1399 code:load_abs("..../user_default").
1401 erl:
1403 If the contents of .erlang are changed and a private version of
1404 user_default is defined, the Erlang/OTP environment can be custom‐
1405 ized. More powerful changes can be made by supplying command-line
1406 arguments in the startup script erl. For more information, see
1407 init(3).
1408
1410 epmd(1), erl_prim_loader(3), erts_alloc(3), init(3), application(3),
1411 auth(3), code(3), erl_boot_server(3), heart(3), net_kernel(3), make(3)
1412Ericsson AB erts 10.3.5.2 erl(1)