How can I parse out a date from string using a regular expression?

Question

I am trying to parse out a DateTime from a string using a regular expression. My issue is that I have a list of strings which need to be sorted by their date in descending order. I want to find a regex that will get the date from the strings. They all look similar but I am not sure how to do it. All help is much appreciated.

This is what the string looks like:

sdfsad[10/16/2014 at 9:52 AM by AJOHNSON]sdfsadf

And I have a list that all have the same type of format.

This is the regex I have so far:

[0-9].[/][0-9].[0-9].*[at]

Your edit between versions 1 and 2 of the question is a little bit strong, I'd recommend completing the question next time, in order to make the progression more visible — samy
– samy, Commented Oct 16, 2014 at 19:55

Jim Mischel · Accepted Answer · 2014-10-16 18:23:14Z

2

If all of your lines take this form:

sdfsad[10/16/2014 at 9:52 AM by AJOHNSON]sdfsadf

Then I would suggest using a regular expression to grab everything from the [ to the space before by, and then pass that string to DateTime.ParseExact or DateTime.TryParseExact.

The regex to extract that bit of text should be straightforward, and using the DateTime parser to get the date and time will be easier than trying to do it with a regular expression.

answered Oct 16, 2014 at 18:23

Jim Mischel

135k25 gold badges197 silver badges377 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user3788671 Over a year ago

Can you help me with the regex? This is what i have but since there can be multiple dates in one string it does not stop right after the first bracketed date. "[0-9].*[/][0-9].*[0-9]... "

Jim Mischel Over a year ago

@user3788671: You'll have to show examples of strings you want to parse the date from. Your original question and the sample string say that there is one date that you want to use for the sort. If that's not correct, then you need to clarify. Edit your question and show more sample strings, including one that has multiple dates.

samy · Accepted Answer · 2014-10-16 19:44:44Z

1

Use a regular expression to extract the components that interest you (date and time), create a datetime from these components and sort each line depending on the date time. you can use a temporary data class in order to help you create the structure you want

public class DataWithTimestamp
{
    public string line {get;set;}
    public DateTime stamp {get;set;}

    public DataWithTimestamp(string data)
    {
        stamp = regex.extract(pattern); // not the correct syntax, set it here
        line = data;
    } 
}

and in your code change your lines to the class, sort on the

var allLines = File.ReadAllLines("file.txt");
var sortedLines = allLines
                      .Select(s => new DataWithTimestamp(s))
                      .OrderBy(data => data.stamp)
                      .Select(data => data.line);

EDIT: this regex should work:

\[(?<date>[\d\/]+) at (?<time>[\d:]+).*\]

find the catpured groups date and time then ParseExact them into the correct DateTime

edited Oct 16, 2014 at 19:44

answered Oct 16, 2014 at 17:33

samy

15k3 gold badges57 silver badges85 bronze badges

4 Comments

user3788671 Over a year ago

okay, I was trying to avoid that but it might be my only option

samy Over a year ago

I don't really see another way, and it feels quite readable to me :)

user3788671 Over a year ago

Well there is also a lot of html element in the actual string but i think the brackets help a little bit with the parsing.

user3788671 Over a year ago

Any chance you can help me with the regex?

Collectives™ on Stack Overflow

How can I parse out a date from string using a regular expression?

2 Answers 2

2 Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related