Extract largest numeric sequence from string (regex, or?) - regex

Question

I have strings similar to the following:
4123499-TESCO45-123
every99999994_54
And I want to extract the largest numeric sequence in each string, respectively:
4123499
99999994
I have previously tried regex (I am using VB6)
Set rx = New RegExp
rx.Pattern = "[^\d]"
rx.Global = True
StringText = rx.Replace(StringText, "")
Which gets me partway there, but it only removes the non-numeric values, and I end up with the first string looking like:
412349945123
Can I find a regex that will give me what I require, or will I have to try another method? Essentially, my pattern would have to be anything that isn't the longest numeric sequence. But I'm not actually sure if that is even a reasonable pattern. Could anyone with a better handle of regex tell me if I am going down a rabbit hole? I appreciate any help!

Answer 1

You cannot get the result by just a regex. You will have to extract all numeric chunks and get the longest one using other programming means.
Here is an example:
Dim strPattern As String: strPattern = "\d+"
Dim str As String: str = "4123499-TESCO45-123"
Dim regEx As New RegExp
Dim matches As MatchCollection
Dim match As Match
Dim result As String
With regEx
.Global = True
.MultiLine = False
.IgnoreCase = False
.Pattern = strPattern
End With
Set matches = regEx.Execute(str)
For Each m In matches
If result < Len(m.Value) Then result = m.Value
Next
Debug.Print result
The \d+ with RegExp.Global=True will find all digit chunks and then only the longest will be printed after all matches are processed in a loop.

Answer 2

That's not solvable with an RE on its own.
Instead you can simply walk along the string tracking the longest consecutive digit group:
For i = 1 To Len(StringText)
If IsNumeric(Mid$(StringText, i, 1)) Then
a = a & Mid$(StringText, i, 1)
Else
a = ""
End If
If Len(a) > Len(longest) Then longest = a
Next
MsgBox longest
(first result wins a tie)

Answer 3

If the two examples you gave, are of a standard where:
<long_number>-<some_other_data>-<short_number>
<text><long_number>_<short_number>
Are the two formats that the strings come in, there are some solutions.
However, if you are searching any string in any format for the longest number, these will not work.
Solution 1
([0-9]+)[_-].*
See the demo
In the first capture group, you should have the longest number for those 2 formats.
Note: This assumes that the longest number will be the first number it encounters with an underscore or a hyphen next to it, matching those two examples given.
Solution 2
\d{6,}
See the demo
Note: This assumes that the shortest number will never exceed 5 characters in length, and the longest number will never be shorter than 6 characters in length

Answer 4

Please, try.
Pure VB. No external libs or objects.
No brain-breaking regexp's patterns.
No string manipulations, so - speed. Superspeed. ~30 times faster than regexp :)
Easy transform on variouse needs.
For example, concatenate all digits from the source string to a single string.
Moreover, if target string is only intermediate step,
so it's possible to manipulate with numbers only.
Public Sub sb_BigNmb()
Dim sSrc$, sTgt$
Dim taSrc() As Byte, taTgt() As Byte, tLB As Byte, tUB As Byte
Dim s As Byte, t As Byte, tLenMin As Byte
tLenMin = 4
sSrc = "every99999994_54"
sTgt = vbNullString
taSrc = StrConv(sSrc, vbFromUnicode)
tLB = LBound(taSrc)
tUB = UBound(taSrc)
ReDim taTgt(tLB To tUB)
t = 0
For s = tLB To tUB
Select Case taSrc(s)
Case 48 To 57
taTgt(t) = taSrc(s)
t = t + 1
Case Else
If CBool(t) Then Exit For ' *** EXIT FOR ***
End Select
Next
If (t > tLenMin) Then
ReDim Preserve taTgt(tLB To (t - 1))
sTgt = StrConv(taTgt, vbUnicode)
End If
Debug.Print "'" & sTgt & "'"
Stop
End Sub
How to handle sSrc = "ev_1_ery99999994_54", please, make by yourself :)
.