## Introduction

Erlang Top, etop, is a tool for presenting information about Erlang processes similar to the information presented by top in UNIX.

## Getting Started

Start Erlang Top in either of the following ways:

Use script etop. Use batch file etop.bat, for example, etop -node tiger@durin.

## Output

The output from Erlang Top is as follows:

`======================================================================================== tiger@durin 13:40:32 Load: cpu 0 Memory: total 1997 binary 33 procs 197 processes 0 code 173 runq 135 atom 1002 ets 95 Pid Name or Initial Func Time Reds Memory MsgQ Current Function ---------------------------------------------------------------------------------------- <127.23.0> code_server 0 59585 78064 0 gen_server:loop/6 <127.21.0> file_server_2 0 36380 44276 0 gen_server:loop/6 <127.2.0> erl_prim_loader 0 27962 3740 0 erl_prim_loader:loop <127.9.0> kernel_sup 0 6998 4676 0 gen_server:loop/6 <127.17.0> net_kernel 62 6018 3136 0 gen_server:loop/6 <127.0.0> init 0 4156 4352 0 init:loop/1 <127.16.0> auth 0 1765 1264 0 gen_server:loop/6 <127.18.0> inet_tcp_dist:accept 0 660 1416 0 prim_inet:accept0/2 <127.5.0> application_controll 0 569 6756 0 gen_server:loop/6 <127.137.0> net_kernel:do_spawn_ 0 553 5840 0 dbg:do_relay_1/1 ========================================================================================`

The header includes some system information:

`Load` `cpu`

Runtime/Wallclock, that is, the percentage of time where the node has been active.

`procs`

The number of processes on the node.

`runq`

The number of processes that are ready to run.

`Memory`

The memory allocated by the node in kilobytes.

For each process the following information is presented:

`Time`

The runtime for the process, that is, the time that the process has been scheduled in.

`Reds`

The number of reductions executed on the process.

`Memory`

The size of the process in bytes, obtained by a call to process_info(Pid,memory).

`MsgQ`

The length of the message queue for the process.

Time and Reds can be presented as accumulated values or as values since the last update.

## Configuration

All configuration parameters can be set at start by adding -OptName Value to the command line, for example:

    % etop -node tiger@durin -setcookie mycookie -lines 15

A list of all valid Erlang Top configuration parameters is available in module etop.

The parameters lines, interval, accumulate, and sort can be changed during runtime with function etop:config/2.

Example:

Change configuration parameter lines with text-based presentation. Before the change, 10 lines are presented as follows:

`======================================================================================== tiger@durin 10:12:39 Load: cpu 0 Memory: total 1858 binary 33 procs 191 processes 0 code 173 runq 2 atom 1002 ets 95 Pid Name or Initial Func Time Reds Memory MsgQ Current Function ---------------------------------------------------------------------------------------- <127.23.0> code_server 0 60350 71176 0 gen_server:loop/6 <127.21.0> file_server_2 0 36380 44276 0 gen_server:loop/6 <127.2.0> erl_prim_loader 0 27962 3740 0 erl_prim_loader:loop <127.17.0> net_kernel 0 13808 3916 0 gen_server:loop/6 <127.9.0> kernel_sup 0 6998 4676 0 gen_server:loop/6 <127.0.0> init 0 4156 4352 0 init:loop/1 <127.18.0> inet_tcp_dist:accept 0 2196 1416 0 prim_inet:accept0/2 <127.16.0> auth 0 1893 1264 0 gen_server:loop/6 <127.43.0> ddll_server 0 582 3744 0 gen_server:loop/6 <127.5.0> application_controll 0 569 6756 0 gen_server:loop/6 ========================================================================================`

Function etop:config/2 is called to change the number of showed lines to 5:

    > etop:config(lines,5).
    ok

After the change, 5 lines are presented as follows:

`(etop@durin)2> ======================================================================================== tiger@durin 10:12:44 Load: cpu 0 Memory: total 1859 binary 33 procs 192 processes 0 code 173 runq 2 atom 1002 ets 95 Pid Name or Initial Func Time Reds Memory MsgQ Current Function ---------------------------------------------------------------------------------------- <127.17.0> net_kernel 183 70 4092 0 gen_server:loop/6 <127.335.0> inet_tcp_dist:do_acc 141 22 1856 0 dist_util:con_loop/9 <127.19.0> net_kernel:ticker/2 155 6 1244 0 net_kernel:ticker1/2 <127.341.0> net_kernel:do_spawn_ 0 0 5840 0 dbg:do_relay_1/1 <127.43.0> ddll_server 0 0 3744 0 gen_server:loop/6 ========================================================================================`

## Print to File

At any time, the current Erlang Top display can be dumped to a text file with function etop:dump/1.

## Stop

To stop Erlang Top, use function etop:stop/0.