How to extract only date and time from a large logfile?

Question

I'd like to extract just date and time values out of a log file.

Here are a couple of lines from the log file:

2022-05-22 13:51:52,689 STATUS [Thread-5] hoststate.HighwayMonitorObserverImpl.localHighwayStateChanged - Highway State Changed [LOCAL APP_HW] to FAILURE.
2022-05-22 13:51:54,448 STATUS [HostStateManager[0]] hoststate.HostStateManager.a - [0] high way state changes : sys1-a - [OK, OK, OK, null]->[DELAY, OK, OK, null]
2022-05-22 13:51:54,450 STATUS [HostStateManager[0]] hoststate.HostStateManager.a - [0] update necessary

Btw I'm trying to parse all dates from the log files into another file and I'm stuck at this moment, thanks to everyone who could help me.

you can try regular expressions with `20[0-9]{2}-[01][1-9]-[0-3][0-9] [0-2][0-9]:[0-5][0-9]:[0-5][0-9],[0-9]{3}` or alike pattern — Dmitry Bychenko, Jan 04 '23 at 10:43

score 1 · Answer 1 · answered Jan 04 '23 at 10:27

I just did it, using this commandline command:

grep -o "[0-9\-]* [0-9\:]*,[0-9]*" file.txt

Explanation:

[0-9\-]* covers the date
[0-9\:]* covers the time, minus the milliseconds
, makes the presence of the comma mandatory
,[0-9]* covers the milliseconds, based on the mandatory comma

You can use this as a basis for your regular expression.

score 0 · Accepted Answer · answered Jan 04 '23 at 10:54

For 250kb size file, you can use the below code using Regex.

using System.Text.RegularExpressions;

// read file
string logFile = File.ReadAllText("abc.txt");

// Use regex
Regex regex = new Regex(@"\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}");
MatchCollection matches = regex.Matches(logFile);

// print all dates
foreach (Match match in matches)
{
    Console.WriteLine(match.Value);
}

How to extract only date and time from a large logfile?

2 Answers2