using reqular expression wrong

Anonymous_Banned275

I am trying to simplify the process

This regular expression works and removes all control code

QString result = inString.remove(QRegularExpression("[^\w\d ]+"));
qDebug() <<"QRegularExpression remove ascii applied \n " << result;

This regal expression DOES NOT WORK
I get run time error

QString::replace: invalid QRegularExpression object

It supposedly remove all control code

result  = inString.remove(QRegularExpression("[^\\u0000-\\u007F]+"));
        qDebug() <<"QRegularExpression remove ascii applied  \n " << result;

return result;

Christian Ehrlicher

@AnneRanch said in using reqular expression wrong:

This regal expression DOES NOT WORK

Because \u0000 and \u007F are not valid for pcre -> https://www.regular-expressions.info/unicode.html#codepoint

JonB

@AnneRanch
As @Christian-Ehrlicher has said.

That should be QRegularExpression("[^\\000-\\177]+")

However it will not do what you intend. It will remove all ASCII characters, as the comment said, and return an empty string.

I suspect you are wanting to try:

result  = inString.remove(QRegularExpression("[^\\000-\\037]+"));

which will remove just the characters you have which are non-ASCII-printable control characters.
Your \u0001\u001B[1;39m\u0002export should result in [1;39mexport.

Anonymous_Banned275

I am not sure linking to other forums is OK , but here is a part of it

I am trying to port the Java code to C++ and this reference claims that
the "controls characters " are identified as "[^\u0000-\u007F]"

and that is my objective "remove" all control characters.

And this removes ascii , not control characters>

QString result = inString.remove(QRegularExpression("[^\000-\037]+"));

and that has been my issue since I started this - remove control characters using this expression "[^\000-\037]+"));

I thin I am not using "remove" and plain "match the expression " correctly .

https://stackoverflow.com/questions/24229262/match-non-printable-non-ascii-characters-and-remove-from-text
public static string RemoveTroublesomeCharacters(string inString)
{
if (inString == null)
{
return null;
}

else
{
    char ch;
    Regex regex = new Regex(@"[^\u0000-\u007F]", RegexOptions.IgnoreCase);
    Match charMatch = regex.Match(inString);

JonB

@AnneRanch
That code you are trying to use is for regular expressions understood by .NET. They are not identical to those used by Qt.

And this removes ascii , not control characters>

QString result = inString.remove(QRegularExpression("[^\\000-\\037]+"));

Just remove the ^ I wrote (I forgot you were removing rather than retaining). Should be:

QString result = inString.remove(QRegularExpression("[\\000-\\037]+"));

VRonin

@AnneRanch said in using reqular expression wrong:

THIS SORT OF WORKS
qDebug() <<"match list " << match.capturedTexts();

HOW TO GET INDIVIDUAL QSTRING HERE

match.captured(0);

JonB

@VRonin
If the OP ever returns to look at the answers to this question, it would be a shame if she did not first try the simple

QString result = inString.remove(QRegularExpression("[\\000-\\037]+"));

at least to see if that is acceptable to her, compared to other more complex regular expression solutions....

[I have said that none proposed so far will be perfect, she would have to deal properly with removing just the ANSI escape sequences if she wants it to be really right.]

ChrisW67

@AnneRanch said in using reqular expression wrong:

I am trying to port the Java code to C++ and this reference claims that
the "controls characters " are identified as "[^\u0000-\u007F]"

Well, that reference is wrong. This is the Unicode basic Latin page, covering code points from 0 through 127 decimal, which were specifically designed to be identical to ASCII codes. You will see that only the first 32 code points (0x0000 through 0x001F) and last code point (0x007f, Del) are non-printables: the remainder are printable characters. There are other non-printables outside this range also.

and that is my objective "remove" all control characters.
And this removes ascii , not control characters>
QString result = inString.remove(QRegularExpression("[^\000-\037]+"));
and that has been my issue since I started this - remove control characters using this expression "[^\000-\037]+"));

The regular expression matches any run of characters that is not in the range 0 to 31 decimal. You ask Qt to remove any character that the pattern matches: it does, leaving only those things in the control character block. You want the opposite of that.

It turns out that the documented regular expression dialect allows the POSIX character classes which can make life easier:

#include <QCoreApplication>
#include <QString>
#include <QRegularExpression>
#include <QDebug>

int main(int argc, char **argv) {
        QCoreApplication app(argc, argv);

        QString testString("ABC\tabc\177DEF-def\n\007");

        // following removes all the ASCII printables (i.e. your broken result)
        QString temp(testString);
        temp.remove(QRegularExpression("[^\\000-\\037]+"));
        qDebug() << testString << "==>" << temp;

        // following removes all except the ASCII printables
        temp = testString;
        temp.remove(QRegularExpression("[\\000-\\037\\177]+"));
        qDebug() << testString << "==>" << temp;

        // Following uses a POSIX character class to remove control characters
        // (which include TAB and NL).
        temp = testString;
        temp.remove(QRegularExpression("[[:cntrl:]]+"));
        qDebug() << testString << "==>" << temp;

        return 0;
}

Output:

"ABC\tabc\u007FDEF-def\n\u0007" ==> "\t\n\u0007"
"ABC\tabc\u007FDEF-def\n\u0007" ==> "ABCabcDEF-def"
"ABC\tabc\u007FDEF-def\n\u0007" ==> "ABCabcDEF-def"

JonB

@ChrisW67 said in using reqular expression wrong:

You want the opposite of that.

I did reply earlier:

Just remove the ^ I wrote (I forgot you were removing rather than retaining). Should be:
QString result = inString.remove(QRegularExpression("[\\000-\\037]+"));

Anonymous_Banned275

JobB please get off your horse - this is a discussions and we all have difference of opinions - which is what discussions are for.
( You remind me of "study group " I had years ago where certain cultures insisted on "we all have to have same opinion and agree ... then we can go home ')
I did state I am porting from Java , hence the source ( I used ) is different...
( I realize things get missed . miss-read etc. )
There are two concepts ( to get the job done ) - so far
identify all ASCII characters
remove all control characters

Here is the code :

#ifdef BYPASS
      
        QRegularExpression re("[^\\w\\d (:/<>) ]+");
        QString result  = inString.remove(re); // keep  all ascii plus some 
        qDebug() <<"remove all controls \n    " << result;
        return result;
#endif
        
        QString result = inString.remove(QRegularExpression("[\\000-\\037]+"));
        qDebug() <<"remove all controls \n    " << result;
        return result;

They both leave some unwanted characters. Those are easy to remove after
"regular expression" is done.
4. Looks as "match" is OK but too complex to accomplish what I want.

AS the original title said - I was using the concept wrong - did not pay attention to actual expression - identifying or deleting stuff.

I really appreciate everybody input , it has been educational.

Cheers

JonB

@AnneRanch said in using reqular expression wrong:

JobB please get off your horse - this is a discussions and we all have difference of opinions - which is what discussions are for.

What are you talking about? I gave you the code you need to remove all non-ASCII chars. That's all. And as usual got abuse back. I know you are rude to everybody, but any reason to single me out? :) Oh, and I just saw you use what I suggested and still are cross with me!

Anonymous_Banned275

@JonB ok let's get serious Your posts are great technically, but you just cannot say it without making comments - such as " if he comes back ..."
"I told you so ..." etc.
I realize that each of us has different way to express stuff and that is perfectly OK .
My gut feeling is - I am not native English speaker and not used to this sentence structure:

" ...YOU can do it this way , I ALREADY TOLD YOU SO . "

In may native language I would say
" ... do it this way, "

Cheers

JonB

@AnneRanch
Ah, OK. The trouble is we seem to tell you stuff and you often seem to ignore it and not act on it. That can be frustrating. But I will (try to) bear in mind what you say when replying in your threads :)

Anonymous_Banned275

SOLVED
use QString "replace" instead...

I need more help making the actual expression

QRegularExpression re("[\000-\037[1;139m]+")

This works BUT deletes EVERY occurrence of "m" .

I like to delete ONLY this string "[1;139m"

PS
can anybody recommend "use regular expressing examples in C++"?
I am getting too many "tutorials" and like to know group recommendation .

This one does not really explain stuff, just looks pretty (IMHO) ,,,

https://www.softwaretestinghelp.com/regex-in-cpp/

JonB

@AnneRanch
It gets harder to write the the regular expression for that case.

In all the examples you have shown so far, like

stream raw line  
  "\u0001\u001B[1;39m\u0002export          \u0001\u001B[0m\u0002Print environment variables"

they all look like

\u0001...\u0002

That means they have an ASCII-1 at the start and an ASCII-2 at the end. If all your cases look like this, then:

line.remove(QRegularExpression("\\001[^\\002]*\\002"));

should get rid of just what you want, and leave no "artefact bits".