I want to learn more about the regex syntax of the search and replace function in eclipse c++.
Does it use it's own regex syntax(in this case anyone knows a good tutorial) or does it use the syntax of another language(like java regex, grep, perl regex)?
Eclipse search and replace feature uses Java regex:
The regular expression must respect Java Regex.
However, one of the peculiarities is that you cannot match zero-legnth strings (i.e. (?=,) won't match the empty string before ,). In such cases, use capturing groups in the regex and use backreferences to those groups in the replacement patterns (e.g. to add newlines after a comma use , in the search and $0\n in the replacement).
Related
Does VSCode have support for numbered backreferences? I'm trying to do a find replace from the dialog but it matches the entire regex and replaces with a literal \1
# Regex
<tr><th align="right">target</th><td><pre>(.*)</pre></td></tr>
What is the regex engine that VSCode actually uses under the hood?
VSCode search and replace feature uses ECMAScript standard for the regex based search, and the replacement backreferences are also those that can be used in JavaScript.
To insert Group 1 value use $1.
However, to replace with the whole match, you may use both $& (as in JavaScript) and $0 (as in PCRE).
And remember to use $$ to insert a single literal $ char.
Note that beginning with Visual Studio Code v.1.31.0 release, as a result of moving to Electron 3.0, you may use all the cool features ECMAScript 2018 provides (like infinite-width lookbehinds).
I am having an issue with trying to figure out how to insert some text after I perform a regex search. I know there is a replace function, but I am not looking for that option, just inserting. The text editor I am using is Notepad2, but I am willing to try this in other text editors.
Here is the example that I have.
TEST|Test2|Test3|Test4
This is what I am looking for
Test|Test2|PrefixTest3|Test4
Notice that I am trying to insert the the phrase "Prefix" after the 2nd pipe and leave everything else alone.
I can successfully query the result by using this regex:
^[^|]*\|[^|]*|
But then I do not know how I can retain everything prior and after the search point. Any ideas?
You could simply use \K inorder to discard the previously matched characters.
^[^|]*\|[^|]*\|\K
Then replace the match with the string prefix.
DEMO
You may easily do that in Notepad2 using the regex-based Replace feature.
Find: ^\([^|]*|[^|]*|\)
Replace: \1Prefix
Details:
^ - start of a line (Notepad2 never overflows line boundaries!)
\([^|]*|[^|]*|\) - Capturing group 1 matching a sequence of:
[^|]* - zero or more chars other than |
| - a literal (yes, no escaping is necessary, both escaped and unescaped | match a literal |) pipe symbol
[^|]*| - see above, gets to the second |.
The replacement contains a \1 backreference that inserts what was captured with the capturing group 1.
NOTE that Notepad2 regex engine is very limited. Here is what the Notepad2 documentation says:
Notepad2 supports only a limited subset of regular expressions, as provided by built-in engine of the Scintilla source code editing component. The advantage is that it has a very small footprint. There's currently no plans to integrate a more advanced regular expressions engine, but this may be an option for future development.
Note: Regular expression search is limited to single lines, only.
Also, you may refer to the inline comments inside Scintilla RESearch.cxx file describing the supported syntax. Bear in mind that the regex type used in the Notepad2 S&R tool is that of POSIX and not all of the described Scintilla regex features will work in the tool.
Note that Notepad2 does not seem to support alternation and limiting quantifiers (similar to Lua patterns), but \w matches Unicode letters together with ASCII ones. Sadly, I could not make ? quantifier work.
^([^|]*\|[^|]*\|)
Try this.Replace by $1prefix.See demo.Just capture the first group and then use it for replace.The first group can be accessed by $1.
http://regex101.com/r/pQ9bV3/11
I have got a weird thing to solve in perl using regular expressions.
Consider the strings -
abcdef000000123
blaDeF002500456
wefdEF120045423
All of these strings are matching with the below regular expression when I tried in C with pcre library support :
???[dD][eE][fF][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]
But I'm unable to achieve the same in perl code. I'm getting some weird errors.
Please help with the piece of perl code with which these two things match.
Thanks in advance...
? is called quantifier that makes preceding pattern or group an optional match. Independently ? doesn't make any sense in regex and you are getting an error like: Quantifier follows nothing in regex.
Following regex should work for you in perl:
...[dD][eE][fF][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]
OR even more concise regex:
.{3}[dD][eE][fF][0-9]{9}
Each dot means match any character.
PS: You probably are getting confused by shell's glob vs regex.
That looks more like a file system regex than a PCRE. In Perl, the ? is a quantifier, not a wild card. You may want to replace them with . to get the same results in anything Perl compatible.
I might use ...[dD][eE][fF][0-9]{9} or even replace the [0-9] with \d.
qr/[A-z]{3}def[0-9]{9}/i
should be the Perl Regex object used to validate the mentioned strings.
Regards
I have tried to use the Notepad++ Search/Replace with a Regular Expression to replace specific words with shorter versions of those words.
I used the following regex to match every word that ends with er (but not er as a word) - and replace the matching words with the same words minus the ending r, using a backreference:
Find what: ([a-zA-z]+e)r
Replace with: $1
But it doesn't replace the matching words, even though it finds them.
However, if I change the backreference syntax to this:
Replace with: \1
Everything works fine.
Why doesn't the $1 backreference work?
What is the difference between the two forms of the backrefernce - \1 and $1?
Notepad++'s earlier versions (v5.9.8 and prior) only supported standard POSIX Regular Expressions. However, full PCRE (Perl Compatible Regular Expression) Search/Replace support was added in version 6.0:
New features and enhancement in Notepad++ 6.0:
PCRE (Perl Compatible Regular Expressions) is supported.
This means that if you're using Notepad++ v6.0 or any newer version (e.g v6.1.5), you can use the PCRE syntax, and use $1 instead of \1 for backreference, but it won't be compatible with earlier versions of Notepad++ (prior to version 6.0). Other than that, they're similar.
For more info regarding the differences between the backreference syntax and the reasons behind the new syntax support, see Backreferences syntax in replacement strings (why dollar sign?).
A useful tutorial on how to use regular expressions in Notepad++ can be found here.
I've got a string:
doCall(valA, val.valB);
Using a regex in GVIM I would like to change this to:
valA = doCall(valA, val.valB);
How would I go about doing this? I use %s for basic regex search and replace in GVIM, but this a bit different from my normal usages.
Thanks
You can use this:
%s/\vdoCall\(<(\w*)>,/\1 = doCall(\1,/
\v enables “more magic” in regular expressions – not strictly necessary here but I usually use it to make the expressions simpler. <…> matches word boundaries and the in-between part matches the first parameter and puts it in the first capture group. The replacement uses \1 to access that capture group and insert into the right two places.