Use \r
instead of \n
.
Substituting by \n
inserts a null character into the text. To get a newline, use \r
. When searching for a newline, you’d still use \n
, however. This asymmetry is due to the fact that \n
and \r
do slightly different things:
\n
matches an end of line (newline), whereas \r
matches a carriage return. On the other hand, in substitutions \n
inserts a null character whereas \r
inserts a newline (more precisely, it’s treated as the input CR). Here’s a small, non-interactive example to illustrate this, using the Vim command line feature (in other words, you can copy and paste the following into a terminal to run it). xxd
shows a hexdump of the resulting file.
echo bar > test
(echo 'Before:'; xxd test) > output.txt
vim test '+s/b/\n/' '+s/a/\r/' +wq
(echo 'After:'; xxd test) >> output.txt
more output.txt
Before:
0000000: 6261 720a bar.
After:
0000000: 000a 720a ..r.
In other words, \n
has inserted the byte 0x00 into the text; \r
has inserted the byte 0x0a.
You can access capturing groups like this:
var myString = "something format_abc";
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;
var myRegexp = new RegExp("(?:^|\s)format_(.*?)(?:\s|$)", "g");
var match = myRegexp.exec(myString);
console.log(match[1]); // abc
And if there are multiple matches you can iterate over them:
var myString = "something format_abc";
var myRegexp = new RegExp("(?:^|\s)format_(.*?)(?:\s|$)", "g");
match = myRegexp.exec(myString);
while (match != null) {
// matched text: match[0]
// match start: match.index
// capturing group n: match[n]
console.log(match[0])
match = myRegexp.exec(myString);
}
Edit: 2019-09-10
As you can see the way to iterate over multiple matches was not very intuitive. This lead to the proposal of the String.prototype.matchAll
method. This new method is expected to ship in the ECMAScript 2020 specification. It gives us a clean API and solves multiple problems. It has been started to land on major browsers and JS engines as Chrome 73+ / Node 12+ and Firefox 67+.
The method returns an iterator and is used as follows:
const string = "something format_abc";
const regexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;
const matches = string.matchAll(regexp);
for (const match of matches) {
console.log(match);
console.log(match.index)
}
As it returns an iterator, we can say it's lazy, this is useful when handling particularly large numbers of capturing groups, or very large strings. But if you need, the result can be easily transformed into an Array by using the spread syntax or the Array.from
method:
function getFirstGroup(regexp, str) {
const array = [...str.matchAll(regexp)];
return array.map(m => m[1]);
}
// or:
function getFirstGroup(regexp, str) {
return Array.from(str.matchAll(regexp), m => m[1]);
}
In the meantime, while this proposal gets more wide support, you can use the official shim package.
Also, the internal workings of the method are simple. An equivalent implementation using a generator function would be as follows:
function* matchAll(str, regexp) {
const flags = regexp.global ? regexp.flags : regexp.flags + "g";
const re = new RegExp(regexp, flags);
let match;
while (match = re.exec(str)) {
yield match;
}
}
A copy of the original regexp is created; this is to avoid side-effects due to the mutation of the lastIndex
property when going through the multple matches.
Also, we need to ensure the regexp has the global flag to avoid an infinite loop.
I'm also happy to see that even this StackOverflow question was referenced in the discussions of the proposal.
Best Answer
For versions before Visual studio 2012:
It works when I do this:
find
include "{[a-zA-Z]+\.h}"
,replace with
include <\1>
.The most relevant parts for your question are the curly braces
{}
and the back reference\1
:\n
references to the n'th group indicated by curly braces in the search expression.For versions Visual studio 2012 & up:
Starting with VS2012 .NET Framework regular expressions are used. So there it should be:
find
include "([a-zA-Z]+\.h)"
,replace with
include <$1>
.