erlaunch

NAME

erlaunch - efficiently execute selected Erlang functions from command line

SYNOPSIS

erlaunch [-p port] [-s shell] [-f] [-c cookie] start
erlaunch [-h host] [-p port] [-s shell] [-f] -c cookie connect
erlaunch status
erlaunch command {argument}

DESCRIPTION

erlaunch start spawns a detached Erlang/OTP BEAM emulator, sets the environment variables ERLAUNCH_HOST, ERLAUNCH_PORT, and ERLAUNCH_COOKIE to refer to that emulator, and starts a subshell. When the subshell is exited, the emulator exits as well.

erlaunch connect connects to an existing emulator, setting the environment variables as erlaunch start.

erlaunch status reports whether a detached emulator is running based on the current settings of environment variables.

erlaunch command arg1 arg2 ... argN looks up the environment variables set by a previous erlaunch start or erlaunch connect, uses them to establish a TCP/IP dialogue with the emulator, and asks the emulator to execute the given command with the given arguments.

OPTIONS

• -h host

  Specify the host on which the server resides. If not given, defaults to 127.0.0.1 (the loopback address.) Only sensible in combination with connect.

• -p port

  Specify the port on which the server is listening, or should be listening. If not given, defaults to 17779. Only sensible in combination with start and connect.

• -s shell

  Specify the shell which should be run once the emulator has launched. If not given, defaults to the value of the SHELL environment variable. Only sensible in combination with start and connect.

• -c cookie

  Specify the cookie which the server is using to authenticate, or should use to authenticate. If not given, a random cookie is generated internally. Only sensible in combination with start and connect; essentially mandatory in combination with connect.

• -f

  Force a new shell to be invoked (with start and connect) and a new emulator to be launched (with start) even if environment variables are set indicating that an emulator has already been launched.

CONFIGURATION

See the example priv/erlaunch.cmds file.

SEE ALSO

erl_call(1), escript(1)

BUGS

Assuredly many.

Ideally, the erlaunch client should contain a break handler that sends an end-of-file condition to the server when interrupted.

It would be very nice to be able to determine whether the server was launched sucessfully before starting the subshell.

erlaunch should be able to determine command from argv[0], so that different symbolic links pointing to the erlaunch executable can invoke different commands.

-h, -p, and -c options are probably sensible in combination with erlaunch command {argument}, but they do not currently have any effect.

send_array is particularly inefficient on both ends. A future version might coalesce the entire array into a single packet.

The protocol could be optimized by having each command say whether it needs arguments, the current working directory, or the environment, and only transferring over the TCP/IP connection, those which are actually needed by the command.