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 Indicates if the system is to load code dynamically (interactive),
260 or if all code is to be loaded during system initialization (embed‐
261 ded); see code(3). Defaults to interactive.
262 -name Name:
264 Makes the Erlang runtime system into a distributed node. This flag
265 invokes all network servers necessary for a node to become distrib‐
266 uted; see net_kernel(3). It is also ensured that epmd runs on the
267 current host before Erlang is started; see epmd(1).and the
268 -start_epmd option.
269 The node name will be Name@Host, where Host is the fully qualified
271 host name of the current host. For short names, use flag -sname
272 instead.
273 Warning:
275 Starting a distributed node without also specifying -proto_dist
276 inet_tls will expose the node to attacks that may give the attacker
277 complete access to the node and in extension the cluster. When using
278 un-secure distributed nodes, make sure that the network is configured
279 to keep potential attackers out.
280 -noinput:
283 Ensures that the Erlang runtime system never tries to read any
284 input. Implies -noshell.
285 -noshell:
287 Starts an Erlang runtime system with no shell. This flag makes it
288 possible to have the Erlang runtime system as a component in a
289 series of Unix pipes.
290 -nostick:
292 Disables the sticky directory facility of the Erlang code server;
293 see code(3).
294 -oldshell:
296 Invokes the old Erlang shell from Erlang/OTP 3.3. The old shell can
297 still be used.
298 -pa Dir1 Dir2 ...:
300 Adds the specified directories to the beginning of the code path,
301 similar to code:add_pathsa/1. Note that the order of the given
302 directories will be reversed in the resulting path.
303 As an alternative to -pa, if several directories are to be
305 prepended to the code path and the directories have a common parent
306 directory, that parent directory can be specified in environment
307 variable ERL_LIBS; see code(3).
308 -pz Dir1 Dir2 ...:
310 Adds the specified directories to the end of the code path, similar
311 to code:add_pathsz/1; see code(3).
312 -path Dir1 Dir2 ...:
314 Replaces the path specified in the boot script; see script(4).
315 -proto_dist Proto:
317 Specifies a protocol for Erlang distribution:
320 inet_tcp:
322 TCP over IPv4 (the default)
323 inet_tls:
325 Distribution over TLS/SSL, See the Using SSL for Erlang Distri‐
326 bution User's Guide for details on how to setup a secure distrib‐
327 uted node.
328 inet6_tcp:
330 TCP over IPv6
331 For example, to start up IPv6 distributed nodes:
333 % erl -name test@ipv6node.example.com -proto_dist inet6_tcp
335 -remsh Node:
337 Starts Erlang with a remote shell connected to Node.
338 -rsh Program:
340 Specifies an alternative to rsh for starting a slave node on a
341 remote host; see slave(3).
342 -run Mod [Func [Arg1, Arg2, ...]] (init flag):
344 Makes init call the specified function. Func defaults to start. If
345 no arguments are provided, the function is assumed to be of arity
346 0. Otherwise it is assumed to be of arity 1, taking the list
347 [Arg1,Arg2,...] as argument. All arguments are passed as strings.
348 See init(3).
349 -s Mod [Func [Arg1, Arg2, ...]] (init flag):
351 Makes init call the specified function. Func defaults to start. If
352 no arguments are provided, the function is assumed to be of arity
353 0. Otherwise it is assumed to be of arity 1, taking the list
354 [Arg1,Arg2,...] as argument. All arguments are passed as atoms. See
355 init(3).
356 -setcookie Cookie:
358 Sets the magic cookie of the node to Cookie; see
359 erlang:set_cookie/2.
360 -shutdown_time Time:
362 Specifies how long time (in milliseconds) the init process is
363 allowed to spend shutting down the system. If Time milliseconds
364 have elapsed, all processes still existing are killed. Defaults to
365 infinity.
366 -sname Name:
368 Makes the Erlang runtime system into a distributed node, similar to
369 -name, but the host name portion of the node name Name@Host will be
370 the short name, not fully qualified.
371 This is sometimes the only way to run distributed Erlang if the
373 Domain Name System (DNS) is not running. No communication can exist
374 between nodes running with flag -sname and those running with flag
375 -name, as node names must be unique in distributed Erlang systems.
376 Warning:
378 Starting a distributed node without also specifying -proto_dist
379 inet_tls will expose the node to attacks that may give the attacker
380 complete access to the node and in extension the cluster. When using
381 un-secure distributed nodes, make sure that the network is configured
382 to keep potential attackers out.
383 -start_epmd true | false:
386 Specifies whether Erlang should start epmd on startup. By default
387 this is true, but if you prefer to start epmd manually, set this to
388 false.
389 This only applies if Erlang is started as a distributed node, i.e.
391 if -name or -sname is specified. Otherwise, epmd is not started
392 even if -start_epmd true is given.
393 Note that a distributed node will fail to start if epmd is not run‐
395 ning.
396 -smp [enable|auto|disable]:
398 -smp enable and -smp start the Erlang runtime system with SMP sup‐
399 port enabled. This can fail if no runtime system with SMP support
400 is available. -smp auto starts the Erlang runtime system with SMP
401 support enabled if it is available and more than one logical pro‐
402 cessor is detected. -smp disable starts a runtime system without
403 SMP support. The runtime system without SMP support is deprecated
404 and will be removed in a future major release.
405 Note:
407 See also flag+S.
408 -version (emulator flag):
411 Makes the emulator print its version number. The same as erl +V.
412
414 erl invokes the code for the Erlang emulator (virtual machine), which
415 supports the following flags:
416 +a size:
418 Suggested stack size, in kilowords, for threads in the async thread
419 pool. Valid range is 16-8192 kilowords. The default suggested stack
420 size is 16 kilowords, that is, 64 kilobyte on 32-bit architectures.
421 This small default size has been chosen because the number of async
422 threads can be large. The default size is enough for drivers deliv‐
423 ered with Erlang/OTP, but might not be large enough for other
424 dynamically linked-in drivers that use the driver_async() function‐
425 ality. Notice that the value passed is only a suggestion, and it
426 can even be ignored on some platforms.
427 +A size:
429 Sets the number of threads in async thread pool. Valid range is
430 0-1024. Defaults to 10 if thread support is available.
431 +B [c | d | i]:
433 Option c makes Ctrl-C interrupt the current shell instead of invok‐
434 ing the emulator break handler. Option d (same as specifying +B
435 without an extra option) disables the break handler. Option i makes
436 the emulator ignore any break signal.
437 If option c is used with oldshell on Unix, Ctrl-C will restart the
439 shell process rather than interrupt it.
440 Notice that on Windows, this flag is only applicable for werl, not
442 erl (oldshell). Notice also that Ctrl-Break is used instead of
443 Ctrl-C on Windows.
444 +c true | false:
446 Enables or disables time correction:
447 true:
449 Enables time correction. This is the default if time correction
450 is supported on the specific platform.
451 false:
453 Disables time correction.
454 For backward compatibility, the boolean value can be omitted. This
456 is interpreted as +c false.
457 +C no_time_warp | single_time_warp | multi_time_warp:
459 Sets time warp mode:
460 no_time_warp:
462 No time warp mode (the default)
463 single_time_warp:
465 Single time warp mode
466 multi_time_warp:
468 Multi-time warp mode
469 +d:
471 If the emulator detects an internal error (or runs out of memory),
472 it, by default, generates both a crash dump and a core dump. The
473 core dump is, however, not very useful as the content of process
474 heaps is destroyed by the crash dump generation.
475 Option +d instructs the emulator to produce only a core dump and no
477 crash dump if an internal error is detected.
478 Calling erlang:halt/1 with a string argument still produces a crash
480 dump. On Unix systems, sending an emulator process a SIGUSR1 signal
481 also forces a crash dump.
482 +e Number:
484 Sets the maximum number of ETS tables.
485 +ec:
487 Forces option compressed on all ETS tables. Only intended for test
488 and evaluation.
489 +fnl:
491 The virtual machine works with filenames as if they are encoded
492 using the ISO Latin-1 encoding, disallowing Unicode characters with
493 code points > 255.
494 For more information about Unicode filenames, see section Unicode
496 Filenames in the STDLIB User's Guide. Notice that this value also
497 applies to command-line parameters and environment variables (see
498 section Unicode in Environment and Parameters in the STDLIB User's
499 Guide).
500 +fnu[{w|i|e}]:
502 The virtual machine works with filenames as if they are encoded
503 using UTF-8 (or some other system-specific Unicode encoding). This
504 is the default on operating systems that enforce Unicode encoding,
505 that is, Windows and MacOS X.
506 The +fnu switch can be followed by w, i, or e to control how
508 wrongly encoded filenames are to be reported:
509 * w means that a warning is sent to the error_logger whenever a
511 wrongly encoded filename is "skipped" in directory listings. This
512 is the default.
513 * i means that those wrongly encoded filenames are silently
515 ignored.
516 * e means that the API function returns an error whenever a wrongly
518 encoded filename (or directory name) is encountered.
519 Notice that file:read_link/1 always returns an error if the link
521 points to an invalid filename.
522 For more information about Unicode filenames, see section Unicode
524 Filenames in the STDLIB User's Guide. Notice that this value also
525 applies to command-line parameters and environment variables (see
526 section Unicode in Environment and Parameters in the STDLIB User's
527 Guide).
528 +fna[{w|i|e}]:
530 Selection between +fnl and +fnu is done based on the current locale
531 settings in the OS. This means that if you have set your terminal
532 for UTF-8 encoding, the filesystem is expected to use the same
533 encoding for filenames. This is default on all operating systems,
534 except MacOS X and Windows.
535 The +fna switch can be followed by w, i, or e. This has effect if
537 the locale settings cause the behavior of +fnu to be selected; see
538 the description of +fnu above. If the locale settings cause the
539 behavior of +fnl to be selected, then w, i, or e have no effect.
540 For more information about Unicode filenames, see section Unicode
542 Filenames in the STDLIB User's Guide. Notice that this value also
543 applies to command-line parameters and environment variables (see
544 section Unicode in Environment and Parameters in the STDLIB User's
545 Guide).
546 +hms Size:
548 Sets the default heap size of processes to the size Size.
549 +hmbs Size:
551 Sets the default binary virtual heap size of processes to the size
552 Size.
553 +hmax Size:
555 Sets the default maximum heap size of processes to the size Size.
556 Defaults to 0, which means that no maximum heap size is used. For
557 more information, see process_flag(max_heap_size, MaxHeapSize).
558 +hmaxel true|false:
560 Sets whether to send an error logger message or not for processes
561 reaching the maximum heap size. Defaults to true. For more informa‐
562 tion, see process_flag(max_heap_size, MaxHeapSize).
563 +hmaxk true|false:
565 Sets whether to kill processes reaching the maximum heap size or
566 not. Default to true. For more information, see
567 process_flag(max_heap_size, MaxHeapSize).
568 +hpds Size:
570 Sets the initial process dictionary size of processes to the size
571 Size.
572 +hmqd off_heap|on_heap:
574 Sets the default value for process flag message_queue_data.
575 Defaults to on_heap. If +hmqd is not passed, on_heap will be the
576 default. For more information, see process_flag(message_queue_data,
577 MQD).
578 +K true | false:
580 Enables or disables the kernel poll functionality if supported by
581 the emulator. Defaults to false (disabled). If the emulator does
582 not support kernel poll, and flag +K is passed to the emulator, a
583 warning is issued at startup.
584 +l:
586 Enables autoload tracing, displaying information while loading
587 code.
588 +L:
590 Prevents loading information about source filenames and line num‐
591 bers. This saves some memory, but exceptions do not contain infor‐
592 mation about the filenames and line numbers.
593 +MFlag Value:
595 Memory allocator-specific flags. For more information, see
596 erts_alloc(3).
597 +pc Range:
599 Sets the range of characters that the system considers printable in
600 heuristic detection of strings. This typically affects the shell,
601 debugger, and io:format functions (when ~tp is used in the format
602 string).
603 Two values are supported for Range:
605 latin1:
607 The default. Only characters in the ISO Latin-1 range can be con‐
608 sidered printable. This means that a character with a code point
609 > 255 is never considered printable and that lists containing
610 such characters are displayed as lists of integers rather than
611 text strings by tools.
612 unicode:
614 All printable Unicode characters are considered when determining
615 if a list of integers is to be displayed in string syntax. This
616 can give unexpected results if, for example, your font does not
617 cover all Unicode characters.
618 See also io:printable_range/0 in STDLIB.
620 +P Number:
622 Sets the maximum number of simultaneously existing processes for
623 this system if a Number is passed as value. Valid range for Number
624 is [1024-134217727]
625 NOTE: The actual maximum chosen may be much larger than the Number
627 passed. Currently the runtime system often, but not always, chooses
628 a value that is a power of 2. This might, however, be changed in
629 the future. The actual value chosen can be checked by calling
630 erlang:system_info(process_limit).
631 The default value is 262144
633 +Q Number:
635 Sets the maximum number of simultaneously existing ports for this
636 system if a Number is passed as value. Valid range for Number is
637 [1024-134217727]
638 NOTE: The actual maximum chosen may be much larger than the actual
640 Number passed. Currently the runtime system often, but not always,
641 chooses a value that is a power of 2. This might, however, be
642 changed in the future. The actual value chosen can be checked by
643 calling erlang:system_info(port_limit).
644 The default value used is normally 65536. However, if the runtime
646 system is able to determine maximum amount of file descriptors that
647 it is allowed to open and this value is larger than 65536, the cho‐
648 sen value will increased to a value larger or equal to the maximum
649 amount of file descriptors that can be opened.
650 On Windows the default value is set to 8196 because the normal OS
652 limitations are set higher than most machines can handle.
653 +R ReleaseNumber:
655 Sets the compatibility mode.
656 The distribution mechanism is not backward compatible by default.
658 This flag sets the emulator in compatibility mode with an earlier
659 Erlang/OTP release ReleaseNumber. The release number must be in the
660 range <current release>-2..<current release>. This limits the emu‐
661 lator, making it possible for it to communicate with Erlang nodes
662 (as well as C- and Java nodes) running that earlier release.
663 Note:
665 Ensure that all nodes (Erlang-, C-, and Java nodes) of a distributed
666 Erlang system is of the same Erlang/OTP release, or from two differ‐
667 ent Erlang/OTP releases X and Y, where all Y nodes have compatibility
668 mode X.
669 +r:
672 Forces ETS memory block to be moved on realloc.
673 +rg ReaderGroupsLimit:
675 Limits the number of reader groups used by read/write locks opti‐
676 mized for read operations in the Erlang runtime system. By default
677 the reader groups limit is 64.
678 When the number of schedulers is less than or equal to the reader
680 groups limit, each scheduler has its own reader group. When the
681 number of schedulers is larger than the reader groups limit, sched‐
682 ulers share reader groups. Shared reader groups degrade read lock
683 and read unlock performance while many reader groups degrade write
684 lock performance. So, the limit is a tradeoff between performance
685 for read operations and performance for write operations. Each
686 reader group consumes 64 byte in each read/write lock.
687 Notice that a runtime system using shared reader groups benefits
689 from binding schedulers to logical processors, as the reader groups
690 are distributed better between schedulers.
691 +S Schedulers:SchedulerOnline:
693 Sets the number of scheduler threads to create and scheduler
694 threads to set online when SMP support has been enabled. The maxi‐
695 mum for both values is 1024. If the Erlang runtime system is able
696 to determine the number of logical processors configured and logi‐
697 cal processors available, Schedulers defaults to logical processors
698 configured, and SchedulersOnline defaults to logical processors
699 available; otherwise the default values are 1. Schedulers can be
700 omitted if :SchedulerOnline is not and conversely. The number of
701 schedulers online can be changed at runtime through erlang:sys‐
702 tem_flag(schedulers_online, SchedulersOnline).
703 If Schedulers or SchedulersOnline is specified as a negative num‐
705 ber, the value is subtracted from the default number of logical
706 processors configured or logical processors available, respec‐
707 tively.
708 Specifying value 0 for Schedulers or SchedulersOnline resets the
710 number of scheduler threads or scheduler threads online, respec‐
711 tively, to its default value.
712 This option is ignored if the emulator does not have SMP support
714 enabled (see flag -smp).
715 +SP SchedulersPercentage:SchedulersOnlinePercentage:
717 Similar to +S but uses percentages to set the number of scheduler
718 threads to create, based on logical processors configured, and
719 scheduler threads to set online, based on logical processors avail‐
720 able, when SMP support has been enabled. Specified values must be >
721 0. For example, +SP 50:25 sets the number of scheduler threads to
722 50% of the logical processors configured, and the number of sched‐
723 uler threads online to 25% of the logical processors available.
724 SchedulersPercentage can be omitted if :SchedulersOnlinePercentage
725 is not and conversely. The number of schedulers online can be
726 changed at runtime through erlang:system_flag(schedulers_online,
727 SchedulersOnline).
728 This option interacts with +S settings. For example, on a system
730 with 8 logical cores configured and 8 logical cores available, the
731 combination of the options +S 4:4 +SP 50:25 (in either order)
732 results in 2 scheduler threads (50% of 4) and 1 scheduler thread
733 online (25% of 4).
734 This option is ignored if the emulator does not have SMP support
736 enabled (see flag -smp).
737 +SDcpu DirtyCPUSchedulers:DirtyCPUSchedulersOnline:
739 Sets the number of dirty CPU scheduler threads to create and dirty
740 CPU scheduler threads to set online when threading support has been
741 enabled. The maximum for both values is 1024, and each value is
742 further limited by the settings for normal schedulers:
743 * The number of dirty CPU scheduler threads created cannot exceed
745 the number of normal scheduler threads created.
746 * The number of dirty CPU scheduler threads online cannot exceed
748 the number of normal scheduler threads online.
749 For details, see the +S and +SP. By default, the number of dirty
751 CPU scheduler threads created equals the number of normal scheduler
752 threads created, and the number of dirty CPU scheduler threads
753 online equals the number of normal scheduler threads online. Dirty‐
754 CPUSchedulers can be omitted if :DirtyCPUSchedulersOnline is not
755 and conversely. The number of dirty CPU schedulers online can be
756 changed at runtime through erlang:system_flag(dirty_cpu_sched‐
757 ulers_online, DirtyCPUSchedulersOnline).
758 The amount of dirty CPU schedulers is limited by the amount of nor‐
760 mal schedulers in order to limit the effect on processes executing
761 on ordinary schedulers. If the amount of dirty CPU schedulers was
762 allowed to be unlimited, dirty CPU bound jobs would potentially
763 starve normal jobs.
764 This option is ignored if the emulator does not have threading sup‐
766 port enabled.
767 +SDPcpu DirtyCPUSchedulersPercentage:DirtyCPUSchedulersOnlinePercent‐
769 age:
770 Similar to +SDcpu but uses percentages to set the number of dirty
771 CPU scheduler threads to create and the number of dirty CPU sched‐
772 uler threads to set online when threading support has been enabled.
773 Specified values must be > 0. For example, +SDPcpu 50:25 sets the
774 number of dirty CPU scheduler threads to 50% of the logical proces‐
775 sors configured and the number of dirty CPU scheduler threads
776 online to 25% of the logical processors available. DirtyCPUSched‐
777 ulersPercentage can be omitted if :DirtyCPUSchedulersOnlinePercent‐
778 age is not and conversely. The number of dirty CPU schedulers
779 online can be changed at runtime through erlang:sys‐
780 tem_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline).
781 This option interacts with +SDcpu settings. For example, on a sys‐
783 tem with 8 logical cores configured and 8 logical cores available,
784 the combination of the options +SDcpu 4:4 +SDPcpu 50:25 (in either
785 order) results in 2 dirty CPU scheduler threads (50% of 4) and 1
786 dirty CPU scheduler thread online (25% of 4).
787 This option is ignored if the emulator does not have threading sup‐
789 port enabled.
790 +SDio DirtyIOSchedulers:
792 Sets the number of dirty I/O scheduler threads to create when
793 threading support has been enabled. Valid range is 0-1024. By
794 default, the number of dirty I/O scheduler threads created is 10,
795 same as the default number of threads in the async thread pool.
796 The amount of dirty IO schedulers is not limited by the amount of
798 normal schedulers like the amount of dirty CPU schedulers. This
799 since only I/O bound work is expected to execute on dirty I/O
800 schedulers. If the user should schedule CPU bound jobs on dirty I/O
801 schedulers, these jobs might starve ordinary jobs executing on
802 ordinary schedulers.
803 This option is ignored if the emulator does not have threading sup‐
805 port enabled.
806 +sFlag Value:
808 Scheduling specific flags.
809 +sbt BindType:
811 Sets scheduler bind type.
812 Schedulers can also be bound using flag +stbt. The only differ‐
814 ence between these two flags is how the following errors are han‐
815 dled:
816 * Binding of schedulers is not supported on the specific plat‐
818 form.
819 * No available CPU topology. That is, the runtime system was not
821 able to detect the CPU topology automatically, and no user-
822 defined CPU topology was set.
823 If any of these errors occur when +sbt has been passed, the run‐
825 time system prints an error message, and refuses to start. If any
826 of these errors occur when +stbt has been passed, the runtime
827 system silently ignores the error, and start up using unbound
828 schedulers.
829 Valid BindTypes:
831 u:
833 unbound - Schedulers are not bound to logical processors, that
834 is, the operating system decides where the scheduler threads
835 execute, and when to migrate them. This is the default.
836 ns:
838 no_spread - Schedulers with close scheduler identifiers are
839 bound as close as possible in hardware.
840 ts:
842 thread_spread - Thread refers to hardware threads (such as
843 Intel's hyper-threads). Schedulers with low scheduler identi‐
844 fiers, are bound to the first hardware thread of each core,
845 then schedulers with higher scheduler identifiers are bound to
846 the second hardware thread of each core,and so on.
847 ps:
849 processor_spread - Schedulers are spread like thread_spread,
850 but also over physical processor chips.
851 s:
853 spread - Schedulers are spread as much as possible.
854 nnts:
856 no_node_thread_spread - Like thread_spread, but if multiple
857 Non-Uniform Memory Access (NUMA) nodes exist, schedulers are
858 spread over one NUMA node at a time, that is, all logical pro‐
859 cessors of one NUMA node are bound to schedulers in sequence.
860 nnps:
862 no_node_processor_spread - Like processor_spread, but if multi‐
863 ple NUMA nodes exist, schedulers are spread over one NUMA node
864 at a time, that is, all logical processors of one NUMA node are
865 bound to schedulers in sequence.
866 tnnps:
868 thread_no_node_processor_spread - A combination of
869 thread_spread, and no_node_processor_spread. Schedulers are
870 spread over hardware threads across NUMA nodes, but schedulers
871 are only spread over processors internally in one NUMA node at
872 a time.
873 db:
875 default_bind - Binds schedulers the default way. Defaults to
876 thread_no_node_processor_spread (which can change in the
877 future).
878 Binding of schedulers is only supported on newer Linux, Solaris,
880 FreeBSD, and Windows systems.
881 If no CPU topology is available when flag +sbt is processed and
883 BindType is any other type than u, the runtime system fails to
884 start. CPU topology can be defined using flag +sct. Notice that
885 flag +sct can have to be passed before flag +sbt on the command
886 line (if no CPU topology has been automatically detected).
887 The runtime system does by default not bind schedulers to logical
889 processors.
890 Note:
892 If the Erlang runtime system is the only operating system process
893 that binds threads to logical processors, this improves the perfor‐
894 mance of the runtime system. However, if other operating system
895 processes (for example another Erlang runtime system) also bind
896 threads to logical processors, there can be a performance penalty
897 instead. This performance penalty can sometimes be severe. If so,
898 you are advised not to bind the schedulers.
899 How schedulers are bound matters. For example, in situations when
902 there are fewer running processes than schedulers online, the
903 runtime system tries to migrate processes to schedulers with low
904 scheduler identifiers. The more the schedulers are spread over
905 the hardware, the more resources are available to the runtime
906 system in such situations.
907 Note:
909 If a scheduler fails to bind, this is often silently ignored, as it
910 is not always possible to verify valid logical processor identi‐
911 fiers. If an error is reported, it is reported to the error_logger.
912 If you want to verify that the schedulers have bound as requested,
913 call erlang:system_info(scheduler_bindings).
914 +sbwt none|very_short|short|medium|long|very_long:
917 Sets scheduler busy wait threshold. Defaults to medium. The
918 threshold determines how long schedulers are to busy wait when
919 running out of work before going to sleep.
920 Note:
922 This flag can be removed or changed at any time without prior
923 notice.
924 +scl true|false:
927 Enables or disables scheduler compaction of load. By default
928 scheduler compaction of load is enabled. When enabled, load bal‐
929 ancing strives for a load distribution, which causes as many
930 scheduler threads as possible to be fully loaded (that is, not
931 run out of work). This is accomplished by migrating load (for
932 example, runnable processes) into a smaller set of schedulers
933 when schedulers frequently run out of work. When disabled, the
934 frequency with which schedulers run out of work is not taken into
935 account by the load balancing logic.
936 +scl false is similar to +sub true, but +sub true also balances
938 scheduler utilization between schedulers.
939 +sct CpuTopology:
941 * <Id> = integer(); when 0 =< <Id> =< 65535
944 * <IdRange> = <Id>-<Id>
946 * <IdOrIdRange> = <Id> | <IdRange>
948 * <IdList> = <IdOrIdRange>,<IdOrIdRange> | <IdOrIdRange>
950 * <LogicalIds> = L<IdList>
952 * <ThreadIds> = T<IdList> | t<IdList>
954 * <CoreIds> = C<IdList> | c<IdList>
956 * <ProcessorIds> = P<IdList> | p<IdList>
958 * <NodeIds> = N<IdList> | n<IdList>
960 * <IdDefs> = <LogicalIds><ThreadIds><CoreIds><Proces‐
962 sorIds><NodeIds> | <LogicalIds><ThreadIds><Cor‐
963 eIds><NodeIds><ProcessorIds>
964 * CpuTopology = <IdDefs>:<IdDefs> | <IdDefs>
966 Sets a user-defined CPU topology. The user-defined CPU topology
968 overrides any automatically detected CPU topology. The CPU topol‐
969 ogy is used when binding schedulers to logical processors.
970 Uppercase letters signify real identifiers and lowercase letters
972 signify fake identifiers only used for description of the topol‐
973 ogy. Identifiers passed as real identifiers can be used by the
974 runtime system when trying to access specific hardware; if they
975 are incorrect the behavior is undefined. Faked logical CPU iden‐
976 tifiers are not accepted, as there is no point in defining the
977 CPU topology without real logical CPU identifiers. Thread, core,
978 processor, and node identifiers can be omitted. If omitted, the
979 thread ID defaults to t0, the core ID defaults to c0, the proces‐
980 sor ID defaults to p0, and the node ID is left undefined. Either
981 each logical processor must belong to only one NUMA node, or no
982 logical processors must belong to any NUMA nodes.
983 Both increasing and decreasing <IdRange>s are allowed.
985 NUMA node identifiers are system wide. That is, each NUMA node on
987 the system must have a unique identifier. Processor identifiers
988 are also system wide. Core identifiers are processor wide. Thread
989 identifiers are core wide.
990 The order of the identifier types implies the hierarchy of the
992 CPU topology. The valid orders are as follows:
993 * <LogicalIds><ThreadIds><CoreIds><ProcessorIds><NodeIds>, that
995 is, thread is part of a core that is part of a processor, which
996 is part of a NUMA node.
997 * <LogicalIds><ThreadIds><CoreIds><NodeIds><ProcessorIds>, that
999 is, thread is part of a core that is part of a NUMA node, which
1000 is part of a processor.
1001 A CPU topology can consist of both processor external, and pro‐
1003 cessor internal NUMA nodes as long as each logical processor
1004 belongs to only one NUMA node. If <ProcessorIds> is omitted, its
1005 default position is before <NodeIds>. That is, the default is
1006 processor external NUMA nodes.
1007 If a list of identifiers is used in an <IdDefs>:
1009 * <LogicalIds> must be a list of identifiers.
1011 * At least one other identifier type besides <LogicalIds> must
1013 also have a list of identifiers.
1014 * All lists of identifiers must produce the same number of iden‐
1016 tifiers.
1017 A simple example. A single quad core processor can be described
1019 as follows:
1020 % erl +sct L0-3c0-3
1022 1> erlang:system_info(cpu_topology).
1023 [{processor,[{core,{logical,0}},
1024 {core,{logical,1}},
1025 {core,{logical,2}},
1026 {core,{logical,3}}]}]
1027 A more complicated example with two quad core processors, each
1029 processor in its own NUMA node. The ordering of logical proces‐
1030 sors is a bit weird. This to give a better example of identifier
1031 lists:
1032 % erl +sct L0-1,3-2c0-3p0N0:L7,4,6-5c0-3p1N1
1034 1> erlang:system_info(cpu_topology).
1035 [{node,[{processor,[{core,{logical,0}},
1036 {core,{logical,1}},
1037 {core,{logical,3}},
1038 {core,{logical,2}}]}]},
1039 {node,[{processor,[{core,{logical,7}},
1040 {core,{logical,4}},
1041 {core,{logical,6}},
1042 {core,{logical,5}}]}]}]
1043 As long as real identifiers are correct, it is OK to pass a CPU
1045 topology that is not a correct description of the CPU topology.
1046 When used with care this can be very useful. This to trick the
1047 emulator to bind its schedulers as you want. For example, if you
1048 want to run multiple Erlang runtime systems on the same machine,
1049 you want to reduce the number of schedulers used and manipulate
1050 the CPU topology so that they bind to different logical CPUs. An
1051 example, with two Erlang runtime systems on a quad core machine:
1052 % erl +sct L0-3c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname one
1054 % erl +sct L3-0c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname two
1055 In this example, each runtime system have two schedulers each
1057 online, and all schedulers online will run on different cores. If
1058 we change to one scheduler online on one runtime system, and
1059 three schedulers online on the other, all schedulers online will
1060 still run on different cores.
1061 Notice that a faked CPU topology that does not reflect how the
1063 real CPU topology looks like is likely to decrease the perfor‐
1064 mance of the runtime system.
1065 For more information, see erlang:system_info(cpu_topology).
1067 +secio true|false:
1069 Enables or disables eager check I/O scheduling. Defaults to true.
1070 The default was changed from false as from ERTS 7.0. The behavior
1071 before this flag was introduced corresponds to +secio false.
1072 The flag effects when schedulers will check for I/O operations
1074 possible to execute, and when such I/O operations will execute.
1075 As the parameter name implies, schedulers are more eager to check
1076 for I/O when true is passed. This, however, also implies that
1077 execution of outstanding I/O operation is not prioritized to the
1078 same extent as when false is passed.
1079 erlang:system_info(eager_check_io) returns the value of this
1081 parameter used when starting the virtual machine.
1082 +sfwi Interval:
1084 Sets scheduler-forced wakeup interval. All run queues are scanned
1085 each Interval milliseconds. While there are sleeping schedulers
1086 in the system, one scheduler is woken for each non-empty run
1087 queue found. Interval default to 0, meaning this feature is dis‐
1088 abled.
1089 Note:
1091 This feature has been introduced as a temporary workaround for
1092 long-executing native code, and native code that does not bump
1093 reductions properly in OTP. When these bugs have be fixed, this
1094 flag will be removed.
1095 +spp Bool:
1098 Sets default scheduler hint for port parallelism. If set to true,
1099 the virtual machine schedules port tasks when it improves paral‐
1100 lelism in the system. If set to false, the virtual machine tries
1101 to perform port tasks immediately, improving latency at the
1102 expense of parallelism. Default to false. The default used can be
1103 inspected in runtime by calling erlang:system_info(port_parallel‐
1104 ism). The default can be overridden on port creation by passing
1105 option parallelism to erlang:open_port/2.
1106 +sss size:
1108 Suggested stack size, in kilowords, for scheduler threads. Valid
1109 range is 20-8192 kilowords. The default suggested stack size is
1110 128 kilowords.
1111 +sssdcpu size:
1113 Suggested stack size, in kilowords, for dirty CPU scheduler
1114 threads. Valid range is 20-8192 kilowords. The default suggested
1115 stack size is 40 kilowords.
1116 +sssdio size:
1118 Suggested stack size, in kilowords, for dirty IO scheduler
1119 threads. Valid range is 20-8192 kilowords. The default suggested
1120 stack size is 40 kilowords.
1121 +stbt BindType:
1123 Tries to set the scheduler bind type. The same as flag +sbt
1124 except how some errors are handled. For more information, see
1125 +sbt.
1126 +sub true|false:
1128 Enables or disables scheduler utilization balancing of load. By
1129 default scheduler utilization balancing is disabled and instead
1130 scheduler compaction of load is enabled, which strives for a load
1131 distribution that causes as many scheduler threads as possible to
1132 be fully loaded (that is, not run out of work). When scheduler
1133 utilization balancing is enabled, the system instead tries to
1134 balance scheduler utilization between schedulers. That is, strive
1135 for equal scheduler utilization on all schedulers.
1136 +sub true is only supported on systems where the runtime system
1138 detects and uses a monotonically increasing high-resolution
1139 clock. On other systems, the runtime system fails to start.
1140 +sub true implies +scl false. The difference between +sub true
1142 and +scl false is that +scl false does not try to balance the
1143 scheduler utilization.
1144 +swct very_eager|eager|medium|lazy|very_lazy:
1146 Sets scheduler wake cleanup threshold. Defaults to medium. Con‐
1147 trols how eager schedulers are to be requesting wakeup because of
1148 certain cleanup operations. When a lazy setting is used, more
1149 outstanding cleanup operations can be left undone while a sched‐
1150 uler is idling. When an eager setting is used, schedulers are
1151 more frequently woken, potentially increasing CPU-utilization.
1152 Note:
1154 This flag can be removed or changed at any time without prior
1155 notice.
1156 +sws default|legacy:
1159 Sets scheduler wakeup strategy. Default strategy changed in ERTS
1160 5.10 (Erlang/OTP R16A). This strategy was known as proposal in
1161 Erlang/OTP R15. The legacy strategy was used as default from R13
1162 up to and including R15.
1163 Note:
1165 This flag can be removed or changed at any time without prior
1166 notice.
1167 +swt very_low|low|medium|high|very_high:
1170 Sets scheduler wakeup threshold. Defaults to medium. The thresh‐
1171 old determines when to wake up sleeping schedulers when more work
1172 than can be handled by currently awake schedulers exists. A low
1173 threshold causes earlier wakeups, and a high threshold causes
1174 later wakeups. Early wakeups distribute work over multiple sched‐
1175 ulers faster, but work does more easily bounce between sched‐
1176 ulers.
1177 Note:
1179 This flag can be removed or changed at any time without prior
1180 notice.
1181 +t size:
1184 Sets the maximum number of atoms the virtual machine can handle.
1185 Defaults to 1,048,576.
1186 +T Level:
1188 Enables modified timing and sets the modified timing level. Valid
1189 range is 0-9. The timing of the runtime system is changed. A high
1190 level usually means a greater change than a low level. Changing the
1191 timing can be very useful for finding timing-related bugs.
1192 Modified timing affects the following:
1194 Process spawning:
1196 A process calling spawn, spawn_link, spawn_monitor, or spawn_opt
1197 is scheduled out immediately after completing the call. When
1198 higher modified timing levels are used, the caller also sleeps
1199 for a while after it is scheduled out.
1200 Context reductions:
1202 The number of reductions a process is allowed to use before it is
1203 scheduled out is increased or reduced.
1204 Input reductions:
1206 The number of reductions performed before checking I/O is
1207 increased or reduced.
1208 Note:
1210 Performance suffers when modified timing is enabled. This flag is
1211 only intended for testing and debugging.
1212 return_to and return_from trace messages are lost when tracing on the
1214 spawn BIFs.
1215 This flag can be removed or changed at any time without prior notice.
1217 +v:
1220 Verbose.
1221 +V:
1223 Makes the emulator print its version number.
1224 +W w | i | e:
1226 Sets the mapping of warning messages for error_logger. Messages
1227 sent to the error logger using one of the warning routines can be
1228 mapped to errors (+W e), warnings (+W w), or information reports
1229 (+W i). Defaults to warnings. The current mapping can be retrieved
1230 using error_logger:warning_map/0. For more information, see
1231 error_logger:warning_map/0 in Kernel.
1232 +zFlag Value:
1234 Miscellaneous flags:
1235 +zdbbl size:
1237 Sets the distribution buffer busy limit (dist_buf_busy_limit) in
1238 kilobytes. Valid range is 1-2097151. Defaults to 1024.
1239 A larger buffer limit allows processes to buffer more outgoing
1241 messages over the distribution. When the buffer limit has been
1242 reached, sending processes will be suspended until the buffer
1243 size has shrunk. The buffer limit is per distribution channel. A
1244 higher limit gives lower latency and higher throughput at the
1245 expense of higher memory use.
1246 +zdntgc time:
1248 Sets the delayed node table garbage collection time
1249 (delayed_node_table_gc) in seconds. Valid values are either
1250 infinity or an integer in the range 0-100000000. Defaults to 60.
1251 Node table entries that are not referred linger in the table for
1253 at least the amount of time that this parameter determines. The
1254 lingering prevents repeated deletions and insertions in the
1255 tables from occurring.
1256
1258 ERL_CRASH_DUMP:
1259 If the emulator needs to write a crash dump, the value of this
1260 variable is the filename of the crash dump file. If the variable is
1261 not set, the name of the crash dump file is erl_crash.dump in the
1262 current directory.
1263 ERL_CRASH_DUMP_NICE:
1265 Unix systems: If the emulator needs to write a crash dump, it uses
1266 the value of this variable to set the nice value for the process,
1267 thus lowering its priority. Valid range is 1-39 (higher values are
1268 replaced with 39). The highest value, 39, gives the process the
1269 lowest priority.
1270 ERL_CRASH_DUMP_SECONDS:
1272 Unix systems: This variable gives the number of seconds that the
1273 emulator is allowed to spend writing a crash dump. When the given
1274 number of seconds have elapsed, the emulator is terminated.
1275 ERL_CRASH_DUMP_SECONDS=0:
1277 If the variable is set to 0 seconds, the runtime system does not
1278 even attempt to write the crash dump file. It only terminates.
1279 This is the default if option -heart is passed to erl and
1280 ERL_CRASH_DUMP_SECONDS is not set.
1281 ERL_CRASH_DUMP_SECONDS=S:
1283 If the variable is set to a positive value S, wait for S seconds
1284 to complete the crash dump file and then terminates the runtime
1285 system with a SIGALRM signal.
1286 ERL_CRASH_DUMP_SECONDS=-1:
1288 A negative value causes the termination of the runtime system to
1289 wait indefinitely until the crash dump file has been completly
1290 written. This is the default if option -heart is not passed to
1291 erl and ERL_CRASH_DUMP_SECONDS is not set.
1292 See also heart(3).
1294 ERL_CRASH_DUMP_BYTES:
1296 This variable sets the maximum size of a crash dump file in bytes.
1297 The crash dump will be truncated if this limit is exceeded. If the
1298 variable is not set, no size limit is enforced by default. If the
1299 variable is set to 0, the runtime system does not even attempt to
1300 write a crash dump file.
1301 Introduced in ERTS 8.1.2 (Erlang/OTP 19.2).
1303 ERL_AFLAGS:
1305 The content of this variable is added to the beginning of the com‐
1306 mand line for erl.
1307 Flag -extra is treated in a special way. Its scope ends at the end
1309 of the environment variable content. Arguments following an -extra
1310 flag are moved on the command line into section -extra, that is,
1311 the end of the command line following an -extra flag.
1312 ERL_ZFLAGS and ERL_FLAGS:
1314 The content of these variables are added to the end of the command
1315 line for erl.
1316 Flag -extra is treated in a special way. Its scope ends at the end
1318 of the environment variable content. Arguments following an -extra
1319 flag are moved on the command line into section -extra, that is,
1320 the end of the command line following an -extra flag.
1321 ERL_LIBS:
1323 Contains a list of additional library directories that the code
1324 server searches for applications and adds to the code path; see
1325 code(3).
1326 ERL_EPMD_ADDRESS:
1328 Can be set to a comma-separated list of IP addresses, in which case
1329 the epmd daemon listens only on the specified address(es) and on
1330 the loopback address (which is implicitly added to the list if it
1331 has not been specified).
1332 ERL_EPMD_PORT:
1334 Can contain the port number to use when communicating with epmd.
1335 The default port works fine in most cases. A different port can be
1336 specified to allow nodes of independent clusters to co-exist on the
1337 same host. All nodes in a cluster must use the same epmd port num‐
1338 ber.
1339
1341 On Unix systems, the Erlang runtime will interpret two types of sig‐
1342 nals.
1343 SIGUSR1:
1345 A SIGUSR1 signal forces a crash dump.
1346 SIGTERM:
1348 A SIGTERM will produce a stop message to the init process. This is
1349 equivalent to a init:stop/0 call.
1350 Introduced in ERTS 8.3 (Erlang/OTP 19.3)
1352 The signal SIGUSR2 is reserved for internal usage. No other signals are
1354 handled.
1355
1357 The standard Erlang/OTP system can be reconfigured to change the
1358 default behavior on startup.
1359 The .erlang startup file:
1361 When Erlang/OTP is started, the system searches for a file named
1362 .erlang in the directory where Erlang/OTP is started. If not found,
1363 the user's home directory is searched for an .erlang file.
1364 If an .erlang file is found, it is assumed to contain valid Erlang
1366 expressions. These expressions are evaluated as if they were input
1367 to the shell.
1368 A typical .erlang file contains a set of search paths, for example:
1370 io:format("executing user profile in HOME/.erlang\n",[]).
1372 code:add_path("/home/calvin/test/ebin").
1373 code:add_path("/home/hobbes/bigappl-1.2/ebin").
1374 io:format(".erlang rc finished\n",[]).
1375 user_default and shell_default:
1377 Functions in the shell that are not prefixed by a module name are
1378 assumed to be functional objects (funs), built-in functions (BIFs),
1379 or belong to the module user_default or shell_default.
1380 To include private shell commands, define them in a module
1382 user_default and add the following argument as the first line in
1383 the .erlang file:
1384 code:load_abs("..../user_default").
1386 erl:
1388 If the contents of .erlang are changed and a private version of
1389 user_default is defined, the Erlang/OTP environment can be custom‐
1390 ized. More powerful changes can be made by supplying command-line
1391 arguments in the startup script erl. For more information, see
1392 init(3).
1393
1395 epmd(1), erl_prim_loader(3), erts_alloc(3), init(3), application(3),
1396 auth(3), code(3), erl_boot_server(3), heart(3), net_kernel(3), make(3)
1397Ericsson AB erts 9.3.3.10 erl(1)