NAME
erl_call - Call/Start a Distributed Erlang Node
DESCRIPTION
erl_call makes it possible to start and/or communicate with a
distributed 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.
EXPORTS
erl_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 [] is assumed
for unspecified Fun and Args. 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,
separated 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
successful.
-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>,
[]}]