Program (om_exec)
This module executes a program or script on startup and writes (pipes) log data to its standard input.
By default, it will write the contents of the $raw_event core field one record per line.
The output format can be changed with the OutputType common module directive.
The program or script is expected to be able to read data from its standard input.
Refer to the Examples below.
When the module stops, which usually happens when NXLog exits and the pipe is closed, it will stop the program or script by sending a SIGTERM (15) signal followed by a SIGKILL (9) signal if the process does not terminate within the stipulated timeout.
| 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. |
If you are using a Python script, we recommend disabling buffering of the stdout and stderr streams using the -u command-line option.
This is because, under certain circumstances, Python’s internal buffering may result in loss of data.
|
Configuration
The om_exec module accepts the following directives in addition to the common module directives. The Command directive is required.
Required directives
The following directives are required for the module to start.
This mandatory directive specifies the name of the program or script to be executed.
|
Optional directives
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 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 |
Examples
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.
<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>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.
<Input log_file>
Module im_file
File '/path/to/log/file'
</Input>
<Output stdout>
Module om_exec
Command /bin/sh
Arg -c
Arg cat $1
</Output>This configuration reads logs from file and pipes the log lines to a Bash script. The Command directive specifies the path to script and the Arg directives specify script arguments.
<Input log_file>
Module im_file
File '/path/to/log/file'
</Input>
<Output bash_script>
Module om_exec
Command /path/to/logreader.sh
Arg -o
Arg /path/to/output.log
</Output>#!/usr/bin/env bash
LOG=./output.log
PIDF=./pidf
ME=$(basename $0)
echo $$ > $PIDF
while getopts o: flag
do
case "${flag}" in
o) # Path to the output log file
LOG=${OPTARG};;
\?) # Invalid option
echo "Error: Invalid option"
exit;;
esac
done
printlog(){
echo "$ME[$$]:$@" >> $LOG
}
trap_function(){
rm $PIDF
exit
}
trap trap_function 15 2
while read LINE; do
printlog "INPUT:$LINE"
done
trap_functionThis 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.
The first Arg directive specifies the -u command-line option to disable buffering for the stdout and stderr streams.
It is recommended to disable buffering because, under certain circumstances, it may lead to loss of data.
The second Arg directive specifies the path to the script, and the following Arg directives specify script arguments.
<Input log_file>
Module im_file
File 'C:\Logs\input.log'
</Input>
<Output python_script>
Module om_exec
Command C:\Python39\python.exe
Arg -u
Arg C:\Scripts\logreader.py
Arg --output-file
Arg C:\Logs\output.log
</Output>import argparse
import sys
arg_parser = argparse.ArgumentParser()
arg_parser.add_argument("--output-file",
type=str,
required=False,
dest="output_file",
default="./output.log",
help="Path to the output log file")
parsed_args = arg_parser.parse_args()
def read_stdin(file_path):
with open(file_path, "a") as fh_stream:
while True:
for line in sys.stdin:
fh_stream.write(line)
fh_stream.flush()
if __name__ == '__main__':
read_stdin(parsed_args.output_file)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. The first Arg directive specifies the path to the script, and the following Arg directives specify script arguments.
<Input log_file>
Module im_file
File 'C:\Logs\input.log'
</Input>
<Output powershell_script>
Module om_exec
Command C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
Arg C:\Scripts\logreader.ps1
Arg -OutputFile
Arg C:\Logs\output.log
</Output>param (
[string]$OutputFile = "$PSScriptRoot\output.log"
)
while ($line = Read-Host)
{
$line | Add-Content -Path $OutputFile
}
