Program (om_exec)

This module will execute a program or script on startup and write (pipe) log data to its standard input. Unless OutputType is set to something else, only the contents of the $raw_event field are sent over the pipe. The execution of the program or script will terminate when the module is stopped, which usually happens when NXLog exits and the pipe is closed.

To examine the supported platforms, see the list of installer packages in the Available Modules chapter.

The program or script is started when NXLog starts and must not exit until the module is stopped. To invoke a program or script for each log message, use xm_exec instead.

Configuration

The om_exec module accepts the following directives in addition to the common module directives. The Command directive is required.

Command

This mandatory directive specifies the name of the program or script to be executed.

Programs, scripts, and commands are executed under the context of the user running NXLog. When NXLog is running as a service, the service user will be used. If the program, script, or command accesses environment variables, make sure that these are available for the NXLog user.

Arg: This is an optional parameter. Arg can be specified multiple times, once for each argument that needs to be passed to the Command. Note that specifying multiple arguments with one Arg directive, with arguments separated by spaces, will not work (the Command will receive it as one argument).

Restart: Restart the process if it exits. There is a one second delay before it is restarted to avoid a denial-of-service when a process is not behaving. Looping should be implemented in the script itself. This directive is only to provide some safety against malfunctioning scripts and programs. This boolean directive defaults to FALSE: the Command will not be restarted if it exits.

Examples

Example 1. Piping logs to an external program

This configuration reads logs from a file and writes the log lines to the standard input of an application. The Command directive specifies the path to the application executable and the Arg directive specifies an application argument.

nxlog.conf

<Input log_file>
    Module      im_file
    File        '/path/to/log/file'
</Input>

<Output myapp>
    Module      om_exec
    Command     /path/to/myapp

    # On Windows the path to the application executable
    # should include the file extension.
    #Command    C:\Program Files\MyApp\myapp.exe

    Arg         --level=info
</Output>

Example 2. Piping logs to the standard output

This configuration reads logs from a file and writes the log lines to the standard output using the Linux cat command-line tool. The Command directive specifies the path to the Linux system shell. The first Arg directive passes the -c argument to the shell and the second Arg directive specifies the command to execute.

nxlog.conf

<Input log_file>
    Module      im_file
    File        '/path/to/log/file'
</Input>

<Output stdout>
    Module      om_exec
    Command     /bin/sh
    Arg         -c
    Arg         cat $1
</Output>

Example 3. Executing a script

This configuration reads logs from a file and pipes the log lines to a Python script. The Command directive specifies the path to the Python executable and the Arg directive specifies the path to the script.

nxlog.conf

<Input log_file>
    Module    im_file
    File      '/path/to/log/file'
</Input>

<Output python_script>
   Module     om_exec
   Command    C:\Python39\python.exe
   Arg        C:\Scripts\myscript.py
</Output>

Example 4. Executing commands under a specific shell

To execute commands under a specific shell, the Command directive should specify the path to the shell executable. The commands to execute can be passed as arguments according to the shell being used. The configuration below executes PowerShell commands from a file.

nxlog.conf

<Input log_file>
    Module    im_file
    File      '/path/to/log/file'
</Input>

<Output powershell_script>
   Module     om_exec
   Command    C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
   Arg        C:\Scripts\myscript.ps1
</Output>