How to remove computer and process names and process ids from syslog

Question

Debian syslog contains repeating infomation like:

Dec 25 09:43:28 uvn-76-202 Eeva[7192]:          at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Dec 25 09:43:28 uvn-76-202 Eeva[7192]:          at Program.<>c.<<Main>b__3_6>d.MoveNext() in C:\raamat\eevaweb\Store\Program.cs:line 979
Dec 25 09:43:28 uvn-76-202 Eeva[7192]:       
Dec 25 09:45:01 uvn-76-202 CRON[18528]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)
Dec 25 09:54:14 uvn-76-202 systemd[1]: Created slice User Slice of UID 0.

How to remove server name, process name, process id and spaces so that output is

Dec 25 09:43:28 at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Dec 25 09:43:28 at Program.<>c.<<Main>b__3_6>d.MoveNext() in C:\raamat\eevaweb\Store\Program.cs:line 979
Dec 25 09:45:01 (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)
Dec 25 09:54:14 Created slice User Slice of UID 0.

Tried to use in ASP.NET 9 MVC controller

  StribBuilder sb = new();
  using StreamReader reader = new("/var/log/syslog");
  string line;
  while ((line = await reader.ReadLineAsync()) != null)
  {
    line = StrTran(line, "uvn-76-202 Eeva", "");
    line = StrTran(line, "         "), "");
    sb.AppendLine(line);
  }

static string StrTran(string cSearchIn, string cSearchFor, string cReplaceWith)
{
  StringBuilder sb = new(cSearchIn);
  return sb.Replace(cSearchFor, cReplaceWith).ToString();
}

but this removes only part of unnessecary information.

Answer 1

using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

public class LogProcessor
{
public static async Task<string> ProcessLogAsync(string logPath)
{
    StringBuilder sb = new();
    using StreamReader reader = new(logPath);

    string line;
    while ((line = await reader.ReadLineAsync()) != null)
    {
        // Use regex to remove the server name, process name, and process 
ID.
        line = Regex.Replace(line, @"\buvn-76-202\b.*?\[\d+\]:\s*", "");

        // Remove leading spaces (if any).
        line = line.TrimStart();

        sb.AppendLine(line);
    }

    return sb.ToString();
    }
}


class Program
{
public static async Task Main(string[] args)
{
    string logPath = "/var/log/syslog";
    string processedLogs = await LogProcessor.ProcessLogAsync(logPath);
    Console.WriteLine(processedLogs);
    }
}

EXplanation:

StringBuilder object is created to efficiently build the cleaned log contents. StreamReader for Reading the File:

The file at logPath is opened for reading using StreamReader, which reads the file asynchronously. Line-by-Line Processing:

The file is read line by line using ReadLineAsync(). For each line: Regex Replacement: A regular expression removes patterns that match a specific format: Example: uvn-76-202... [1234]: Regex: \buvn-76-202\b: Matches the server name uvn-76-202 exactly. .?: Matches any characters up to the next part. [\d+]: Matches a process ID enclosed in square brackets (e.g., [1234]). :\s: Matches a colon followed by optional spaces. Trim Leading Spaces: Removes any spaces at the start of the line after the regex operation.

Each cleaned line is appended to the StringBuilder object. Return Cleaned Log After all lines are processed, the cleaned log is returned as a single string. Program Class In order to serve as the entry point for the application. Method Steps: Define Log Path: The path to the log file is set (/var/log/syslog). Call ProcessLogAsync: The log is processed asynchronously using the LogProcessor. Display Cleaned Logs: The processed log is printed to the console.