![[Erlang Systems]](min_head.gif)
The erl program starts the Erlang runtime system.
The exact details (e.g. whether erl is a script or a program
and which other programs it calls) are system-dependent.
Windows 95/98/2000/NT users will probably want to use the werl
program instead, which run in its own window with scrollbars and
supports command-line editing.
The erl program on Windows provides no line editing in its
shell, and on Windows 95 there is no way to scroll back to text which
has scrolled off the screen.
The erl program must be used, however, in pipelines or if you want
to redirect standard input or output.
erl <arguments>
Starts the Erlang system.
Any argument starting with a plus sign (+) is always interpreted
as a system flag (described below), regardless of where it occurs
on the command line (except after the flag -extra).
Arguments starting with a hyphen (-) are the start of
a flag. A flag includes all following arguments up to the next
argument starting with a hyphen.
Example:
erl -sname arne -myflag 1 -s mod func arg
Here -sname arne is a flag and so are -myflag 1
and -s mod func arg. Note that these flags are treated
differently. -sname arne is interpreted by the OTP system,
but it still included in the list of flags returned by
init:get_arguments/0. -s mod func arg is also
treated specially and it is not included in the return value
for init:get_arguments/0. Finally, -myflag 1 is
not interpreted by the OTP system in any way, but it is
included in init:get_arguments/0.
Plain arguments are not interpreted in any way. They
can be retrieved using init:get_plain_arguments/0. Plain
arguments
can occur in the following places: Before the first flag argument on
the command line, or after a -- argument. Additionally,
the flag -extra causes everything that follows to become
plain arguments.
The following flags are supported:
-- will not be interpreted
in any way. They can be retrieved by init:get_plain_arguments/0.
The exception is arguments starting with a +, which will
be interpreted as system flags (see below).
Key configuration parameter of the
AppName application. See application(3).
This type of flag can also be retrieved using the init module.
File.boot,
which is used to start the system. See init(3). Unless
File contains an absolute path, the system searches for File.boot in the current and <ERL_INSTALL_DIR>/bin directories.
<ERL_INSTALL_DIR>/bin/start.boot boot script is used.
<ERL_INSTALL_DIR>/lib directory. $Var is expanded
to Directory in the boot script.
mod1.erl mod2.erl .... and
then terminate (with non-zero exit code if the compilation of some
file didn't succeed). Implies -noinput.
Not recommended - use erlc(1) instead.
Config.config configuration file in order to
configure the system. See application(3).
global will not
maintain a fully connected network of distributed erlang
nodes, and then global name registration cannot be used.
See global(3).-setcookie.
Use -setcookie Cookie option if want to override the default
cookie.
Variable to the value Value
of the Erlang system. For example:
% erl -env DISPLAY gin:0
In this example, an Erlang system is started with the DISPLAY environment
variable set to the value gin:0.
-extra will not be interpreted
in any way. They can be retrieved by init:get_plain_arguments/0.
nodes/0
on the other node. See also hidden global groups,
global_group(3).
-loader inet
flag is present. On each host, there must be one Erlang node running,
on which the boot_server must be started.
Id must be identical to the name
supplied together with the -sname or -name distribution
flags.
instrument. Functionally, it behaves exactly like
an ordinary Erlang system.
Loader can be efile (use the
local file system), or inet (load using the
boot_server on another Erlang node). If Loader is
something else, the user supplied Loader port program is
started.
-loader flag is omitted efile is assumed.
make:all() in the
current work directory and then terminate. See make(3).
Implies -noinput.
Module.
Only supported on Unix.
Mode can be either
interactive to allow automatic code loading, or
embedded to load all code during start-up. See code(3).
Name@Host, where
Host is the fully qualified host name of the current host.
This flag also ensures that epmd runs on
the current host before Erlang is started.
See epmd(1).
-noshell.
code server.
See code(3).
Directories to the head of the search
path of the code server, as if code:add_pathsa/1 was
called. See code(3).
Directories to the end of the search
path of the code server, as if code:add_pathsa/1 was
called. See code(3).
-run flag to the init:boot() routine.
See init(3).
-s flag to the init:boot() routine.
See init(3).
Cookie.
As erlang:set_cookie(node(),Cookie) is used, all
other nodes will also be assumed to have their cookies
set to Cookie. In this way, several nodes can
share one magic cookie. Erlang magic cookies are explained
in auth(3).
-name flag, with the exception that
the host name portion of the node name will not be fully qualified.
The following command is used do start Erlang at the host with the name gin.eua.ericsson.se
% erl -sname klacke
Eshell V4.7 (abort with ^G)
(klacke@gin)1>
Only the host name portion of the node name will be relevant. This is
sometimes the only way to run distributed Erlang if the DNS (Domain
Name System) is not running. There can be no communication between
systems running with the -sname flag and those running with
the -name flag, as node names must be unique in distributed
Erlang systems.
All these flags are processed during the start-up of the Erlang
kernel servers and before any user processes are started.
All flags are passed to init:boot(Args). See init(3).
All additional flags passed to the script will be passed to
init:boot/2 as well, and they can be accessed using
the init module.
The erl script invokes the code for the Erlang virtual
machine. This program supports the following flags:
size.
libc, and elib (some
malloc libraries may not be available on some operating systems).
By default libc is used.
Number must be in the range [16, 262144].
sl_alloc specific flags, see
sl_alloc(3) for further
information.sbrk()) that
will be keept by the allocator (not released to the operating
system). When the amount of free memory at the top of the heap
exceeds the trim threshold, the allocator will release it (by
calling sbrk()). Threshold is given in kilobytes.
Default trim threshold is 128 kilobytes.
sbrk() is called to get more
memory from the operating system. TopPad is given
in kilobytes. Default top pad size is 0 kilobytes.
 |
Regarding memory allocation flags: Only use the +S*, +T, +t, +m, and +d flags if you are absolutely sure what you are doing. Unsuitable settings may cause serious performance degradation (and even a system crash) at any time during operation. Most of these flags are highly implementation dependent, and they may be changed or removed without prior notice. The memory allocator may use other values than those passed to it (even ignore them). It will for example most likely page align threshold values. Observe that the |
Example:
% erl -name foo +B +l
In this example, a distributed node is started with the break handler turned off and a lot of info is displayed while the code is loading.
init(3), erl_prim_loader(3), erl_boot_server(3), code(3), application(3), heart(3), net_kernel(3), auth(3), make(3), epmd(1), sl_alloc(3)