erl_call(1) User Commands erl_call(1)NAMEerl_call - Call/Start a Distributed Erlang Node
DESCRIPTIONerl_call makes it possible to start and/or communicate with a distrib‐
uted Erlang node. It is built upon the erl_interface library as an
example application. Its purpose is to use an Unix shell script to
interact with a distributed Erlang node. It performs all communication
with the Erlang rex server, using the standard Erlang RPC facility. It
does not require any special software to be run at the Erlang target
node.
The main use is to either start a distributed Erlang node or to make an
ordinary function call. However, it is also possible to pipe an Erlang
module to erl_call and have it compiled, or to pipe a sequence of
Erlang expressions to be evaluated (similar to the Erlang shell).
Options, which cause stdin to be read, can be used with advantage as
scripts from within (Unix) shell scripts. Another nice use of erl_call
could be from (http) CGI-bin scripts.
EXPORTSerl_call <options>
Each option flag is described below with its name, type and
meaning.
-a [Mod [Fun [Args]]]]:
(optional): Applies the specified function and returns the
result. Mod must be specified, however start and [] are
assumed for unspecified Fun and Args, respectively. Args
should be in the same format as for erlang:apply/3. Note
that this flag takes exactly one argument, so quoting may be
necessary in order to group Mod, Fun and Args, in a manner
dependent on the behavior of your command shell.
-c Cookie:
(optional): Use this option to specify a certain cookie. If
no cookie is specified, the ~/.erlang.cookie file is read
and its content are used as cookie. The Erlang node we want
to communicate with must have the same cookie.
-d:
(optional): Debug mode. This causes all IO to be output to
the file ~/.erl_call.out.Nodename, where Nodename is the
node name of the Erlang node in question.
-e:
(optional): Reads a sequence of Erlang expressions, sepa‐
rated by ',' and ended with a '.', from stdin until EOF
(Control-D). Evaluates the expressions and returns the
result from the last expression. Returns {ok,Result} if suc‐
cessful.
-h HiddenName:
(optional): Specifies the name of the hidden node that
erl_call represents.
-m:
(optional): Reads an Erlang module from stdin and compiles
it.
-n Node:
(one of -n, -name, -sname is required): Has the same meaning
as -name and can still be used for backwards compatibility
reasons.
-name Node:
(one of -n, -name, -sname is required): Node is the name of
the node to be started or communicated with. It is assumed
that Node is started with erl -name, which means that fully
qualified long node names are used. If the -s option is
given, an Erlang node will (if necessary) be started with
erl -name.
-q:
(optional): Halts the Erlang node specified with the -n
switch. This switch overrides the -s switch.
-r:
(optional): Generates a random name of the hidden node that
erl_call represents.
-s:
(optional): Starts a distributed Erlang node if necessary.
This means that in a sequence of calls, where the '-s' and
'-n Node' are constant, only the first call will start the
Erlang node. This makes the rest of the communication very
fast. This flag is currently only available on the Unix
platform.
-sname Node:
(one of -n, -name, -sname is required): Node is the name of
the node to be started or communicated with. It is assumed
that Node is started with erl -sname which means that short
node names are used. If -s option is given, an Erlang node
will be started (if necessary) with erl -sname.
-v:
(optional): Prints a lot of verbose information. This is
only useful for the developer and maintainer of erl_call.
-x ErlScript:
(optional): Specifies another name of the Erlang start-up
script to be used. If not specified, the standard erl start-
up script is used.
EXAMPLES
Starts an Erlang node and calls erlang:time/0.
erl_call-s -a 'erlang time' -n madonna
{18,27,34}
Terminates an Erlang node by calling erlang:halt/0.
erl_call-s -a 'erlang halt' -n madonna
An apply with several arguments.
erl_call-s -a 'lists map [{math,sqrt},[1,4,9,16,25]]' -n madonna
Evaluates a couple of expressions. The input ends with EOF (Control-D)
.
erl_call-s -e -n madonna
statistics(runtime),
X=1,
Y=2,
{_,T}=statistics(runtime),
{X+Y,T}.
^D
{ok,{3,0}}
Compiles a module and runs it. Again, the input ends with EOF (Control-
D) . (In the example shown, the output has been formatted afterwards).
erl_call-s -m -a lolita -n madonna
-module(lolita).
-compile(export_all).
start() ->
P = processes(),
F = fun(X) -> {X,process_info(X,registered_name)} end,
lists:map(F,[],P).
^D
[{<madonna@chivas.du.etx.ericsson.se,0,0>,
{registered_name,init}},
{<madonna@chivas.du.etx.ericsson.se,2,0>,
{registered_name,erl_prim_loader}},
{<madonna@chivas.du.etx.ericsson.se,4,0>,
{registered_name,error_logger}},
{<madonna@chivas.du.etx.ericsson.se,5,0>,
{registered_name,application_controller}},
{<madonna@chivas.du.etx.ericsson.se,6,0>,
{registered_name,kernel}},
{<madonna@chivas.du.etx.ericsson.se,7,0>,
[]},
{<madonna@chivas.du.etx.ericsson.se,8,0>,
{registered_name,kernel_sup}},
{<madonna@chivas.du.etx.ericsson.se,9,0>,
{registered_name,net_sup}},
{<madonna@chivas.du.etx.ericsson.se,10,0>,
{registered_name,net_kernel}},
{<madonna@chivas.du.etx.ericsson.se,11,0>,
[]},
{<madonna@chivas.du.etx.ericsson.se,12,0>,
{registered_name,global_name_server}},
{<madonna@chivas.du.etx.ericsson.se,13,0>,
{registered_name,auth}},
{<madonna@chivas.du.etx.ericsson.se,14,0>,
{registered_name,rex}},
{<madonna@chivas.du.etx.ericsson.se,15,0>,
[]},
{<madonna@chivas.du.etx.ericsson.se,16,0>,
{registered_name,file_server}},
{<madonna@chivas.du.etx.ericsson.se,17,0>,
{registered_name,code_server}},
{<madonna@chivas.du.etx.ericsson.se,20,0>,
{registered_name,user}},
{<madonna@chivas.du.etx.ericsson.se,38,0>,
[]}]
Ericsson AB erl_interface 3.7.20 erl_call(1)
