How to extract date section from filename?

Question

I need to find a regex to extract date section from the name of several files.

In particular I have these two formats:

ATC0200720140828080610.xls
ATC0200720140901080346_UFF_ACC.xls

I use these two regex to check file name format:

^ATC02007[0-9]{14}.xls$
^ATC02007[0-9]{14}_UFF_ACC.xls$

But I need a regex to extract a specific section:

constant | yyyyMMddHHmmss |   constant
    ^            ^               ^
ATC02007 | 20140901080346 | _UFF_ACC.xls

Both regex I'm using match the entire file name, so I can't use to extract the middle section, so which is the right expression?

how about `fileName.substring(8,8 + 14)`? (not sure about the values) — assylias, Sep 19 '14 at 14:01
possible duplicate of [Using Regular Expressions to Extract a Value in Java](http://stackoverflow.com/questions/237061/using-regular-expressions-to-extract-a-value-in-java) — PM 77-1, Sep 19 '14 at 14:05

score 2 · Accepted Answer · answered Sep 19 '14 at 14:04

2

You are almost there. Just use round brackets to contain the numbers you want.

^ATC02007([0-9]{14})(_UFF_ACC)?.xls$

See example. The numbers are captured in group 1$1.

answered Sep 19 '14 at 14:04

Steven Xu

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Avinash Raj · Answer 2 · 2014-09-19T14:10:53.590

You need to use capturing groups.

^(ATC02007)([0-9]{14})((?:[^.]*)?\\.xls)$

DEMO

GRoup index 1 contains the first constant and group 2 contains date and time and group 3 contains the third constant.

String s = "ATC0200720140828080610.xls\n" + 
        "ATC0200720140901080346_UFF_ACC.xls";
Pattern regex = Pattern.compile("(?m)^(ATC02007)([0-9]{14})((?:[^.]*)?\\.xls)$");
 Matcher matcher = regex.matcher(s);
 while(matcher.find()){
        System.out.println(matcher.group(1));
        System.out.println(matcher.group(2));
        System.out.println(matcher.group(3));
}

Output:

ATC02007
20140828080610
.xls
ATC02007
20140901080346
_UFF_ACC.xls

or `^(.*)([0-9]{14})((?:[^.]*)?\.xls)$` – Avinash Raj Sep 19 '14 at 14:08 — Avinash Raj, Sep 19 '14 at 14:08

How to extract date section from filename?

2 Answers2