Regex to extract numeric string

Question

Hi I don't feel very well with regular expressions. What I would like to achieve is to extract a numeric substring (only 0-9 digits) from the input string.

The numeric string that is searched should be preceded only by a semicolon (;), space ( ) or should be placed exactly at the begining of the input (not line).
The numeric string that is searched should be followed only by a semicolon (;), the end of line or the end of the input string.

Exemplary input:

;x; ;SrvId=3993;ad257c823; 435223;

Output:

435223

I tried: [ \A|;|[ ]]\d*[\r|;|\Z] but it did not worked, it did not even compiled.

FailedDev · Accepted Answer · 2011-10-12 08:55:35Z

2

Try this one:

string resultString = null;
try {
    resultString = Regex.Match(subjectString, @"(?<=\A|\s+|;)(\d+)(?=$|;|\Z)").Groups[1].Value;
} catch (ArgumentException ex) {
    // Syntax error in the regular expression
}

Break down :

(?<=\A|\s+|;)

Posiive lookbehind : start of input or at least one whitespace character or a semicolon.

(\d+) at least one digit

(?=$|;|\Z)

Positive lookahead either end of line, or semicolon or and of input.

Input : ;x; ;SrvId=3993;ad257c823; 435223;

Output of group 1 : 435223

edited Oct 12, 2011 at 8:55

answered Oct 12, 2011 at 8:49

FailedDev

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5 Comments

FailedDev Over a year ago

@HasanKhan Can you provide an input which makes it to match where it shouldn't match?

Muhammad Hasan Khan Over a year ago

@FailedDev it doesn't match the number at the end of line when there is more text in new line

FailedDev Over a year ago

@HasanKhan I don't see any new line in OP examples. Do you?

Muhammad Hasan Khan Over a year ago

@FailedDev "The numeric string that is searched should be followed only by a semicolon (;), the end of line or the end of the input string."

FailedDev Over a year ago

@HasanKhan You can write whatever bold letters you want, however this still doesn't change the fact that there is no new line in the OPs post :) Also if my english don't deceive me the end of line should be the last part of the string. OP doesn't mention possibility of multiple new lines. So you are wrong - again :D

Aziz Shaikh · Accepted Answer · 2011-10-12 08:55:00Z

1

Try this regex:

^(?:[; ]?)(?:.*?)([0-9]+);$

answered Oct 12, 2011 at 8:55

Aziz Shaikh

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Comments

user489998 · Accepted Answer · 2011-10-12 08:55:35Z

1

Using ^.*[ ;](\d+)[;\n]?$ will capture the numbers you're interested in although you may have to change the \n to \r\n depending on the line endings of your input file.

answered Oct 12, 2011 at 8:55

user489998

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Comments

Fischermaen · Accepted Answer · 2011-10-12 08:45:55Z

0

The regular expression should be this:

"[; ]{1}[0-9]+($|[^0-9]+)"

answered Oct 12, 2011 at 8:45

Fischermaen

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1 Comment

Simon Hughes Over a year ago

This returns 435223; which includes the semi-colon

Chief · Accepted Answer · 2011-10-12 09:03:18Z

0

Try using this expression

(\d+\.?\d*|\.\d+)

answered Oct 12, 2011 at 9:03

Chief

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