I have the following code:
String newStr = "aa\$";
print newStr;
print "wwwww ? eeee".replaceFirst("\\?", "'${newStr}'"); // (3)
and I keep getting -- at line 3 -- the following error:
Caught: java.lang.IllegalArgumentException: Illegal group reference
at com.example.MyBuilder.main(MyBuilder.groovy:196)
It looks like that replaceFirst ignores that $ was escaped. How could I let my code run? Does anybody experience such an error?
First
String newStr == "aa\$"
should be
String newStr = "aa\$"
Then, because you are using normal strings to declare your regex, you need to double escape the dollar sign:
String newStr = "aa\\$"
Or, use slashy strings:
String newStr = /aa\$/
I have found a working solution for my problem: String newStr == "aa\\\$";
You need to have three backslashes. The first backslash (from right to left) escapes $ so Groovy Interpreter does not understand $ as a mark for a variable.
The two following slashes has to escape $ for replaceFirst, because $ is interpreted by Matcher.appendReplacement() -- called inside replaceFirst -- as a grouping. It is an unexpected but well documented in JavaDoc behavior:
backslashes (\) and dollar signs ($) in the
replacement string may cause the
results to be different than if it
were being treated as a literal
replacement string
ps. After fighting with escaping other "special" symbol -- backslash -- I switched to String.replace(CharSequence,CharSequence).
Related
I'm having trouble escaping double dollars from a string to be used with regex functions pattern/matcher.
This is part of the String:
WHERE oid_2 = $$test$$ || oid_2 = $$test2$$
and this is the closest code I've tried to get near the solution:
List<String> strList = new ArrayList<String>();
Pattern pattern = Pattern.compile("\$\$.*?\$\$");
log.debug("PATTERN: "+pattern)
Matcher matcher = pattern.matcher(queryText);
while (matcher.find()) {
strList.add(matcher.group());
}
log.debug(strList)
This is the debug output i get
- PATTERN: $$.*?$$
- []
So the pattern is actually right, but the placeholders are not found in the string.
As a test I've tried to replace "$$test$$" with "XXtestXX" and everything works perfectly. What am I missing? I've tried "/$" strings, "\\" but still have no solution.
Note that a $ in regex matches the end of the string. To use it as a literal $ symbol, you need to escape it with a literal backslash.
You used "\$\$.*?\$\$" that got translated into a literal string like $$.*?$$ that matches 2 end of string positions, any 0+ chars as few as possible and then again 2 end of strings, which has little sense. You actually would need a backslash to first escape the $ that is used in Groovy to inject variables into a double quoted string literal, and then use 2 backslashes to define a literal backslash - "\\\$\\\$.*?\\\$\\\$".
However, when you work with regex, slashy strings are quite helpful since all you need to escape a special char is a single backslash.
Here is a sample code extracting all matches from the string you have in Groovy:
def regex = /\$\$.*?\$\$/;
def s = 'WHERE oid_2 = $$test$$ || oid_2 = $$test2$$'
def m = s =~ regex
(0..<m.count).each { print m[it] + '\n' }
See the online demo.
Anyone who gets here might like to know another answer to this, if you want to use Groovy slashy strings:
myComparisonString ==~ /.*something costs [$]stuff.*/
I couldn't find another way of putting a $ in a slashy string, at least if the $ is to be followed by text. If, conversely, it is followed by a number (or presumably any non-letter), this will work:
myComparisonString ==~ /.*something costs \$100.*/
... the trouble being, of course, that the GString "compiler" (if that's its name) would recognise "$stuff" as an interpolated variable.
So I am experiencing some inconsistent behavior in my regex
My regex:
(?<=test\\\\)(.*)(?=\",)
The input string:
"test.exe /c echo teststring > \\\\.\\test\\teststring",
When I run this in https://Regex101.com
I get the value teststring however when I run this in F#
Regex.Match(inputString, "(?<=test\\\\)(.*)(?=\",)")
I get \teststring back. My goal is to get just teststring. I'm not sure what I'm doing wrong.
I had success using triple quoted strings. Then only the regex escapes need be considered, and not the F# string escapes.
let inputString = """test.exe /c echo teststring > \\\\.\\test\\teststring","""
let x = Regex.Match(inputString, """(?<=test\\\\)(.*)(?=\",)""")
"teststring" comes out
The string in your source comes out as
(?<=test\\)(.*)(?=",)
If you don't want to use triple quotes or verbatim, you will have to write this in F# :
"(?<=test\\\\\\\\)(.*)(?=\\\",)"
This string in F# uses backslashes to escape backslashes and a quote character. There are eight backslashes in a row in one place, and this then becomes four actual backslashes in the string value. There is also this:
\\\"
which translates to one actual \ and one actual " in the actual string value.
So then we end up with a string value of
(?<=test\\\\)(.*)(?=\",)
This then is the actual string value fed to the regex engine. The regex engine, like the F# compiler, also uses the backslash to escape characters. That's why any actual backslash had to be doubled and then doubled again.
In Javascript, when I put a backslash in some variables like:
var ttt = "aa ///\\\";
var ttt = "aa ///\";
Javascript shows an error.
If I try to restrict user in entering this character, I also get an error:
(("aaa ///\\\").indexOf('"') != -1)
Restricting backslashes from user input is not a good strategy, because you have to show an annoying message to the user.
Why am I getting an error with backslash?
The backslash (\) is an escape character in Javascript (along with a lot of other C-like languages). This means that when Javascript encounters a backslash, it tries to escape the following character. For instance, \n is a newline character (rather than a backslash followed by the letter n).
In order to output a literal backslash, you need to escape it. That means \\ will output a single backslash (and \\\\ will output two, and so on). The reason "aa ///\" doesn't work is because the backslash escapes the " (which will print a literal quote), and thus your string is not properly terminated. Similarly, "aa ///\\\" won't work, because the last backslash again escapes the quote.
Just remember, for each backslash you want to output, you need to give Javascript two.
You may want to try the following, which is more or less the standard way to escape user input:
function stringEscape(s) {
return s ? s.replace(/\\/g,'\\\\').replace(/\n/g,'\\n').replace(/\t/g,'\\t').replace(/\v/g,'\\v').replace(/'/g,"\\'").replace(/"/g,'\\"').replace(/[\x00-\x1F\x80-\x9F]/g,hex) : s;
function hex(c) { var v = '0'+c.charCodeAt(0).toString(16); return '\\x'+v.substr(v.length-2); }
}
This replaces all backslashes with an escaped backslash, and then proceeds to escape other non-printable characters to their escaped form. It also escapes single and double quotes, so you can use the output as a string constructor even in eval (which is a bad idea by itself, considering that you are using user input). But in any case, it should do the job you want.
You have to escape each \ to be \\:
var ttt = "aa ///\\\\\\";
Updated: I think this question is not about the escape character in string at all. The asker doesn't seem to explain the problem correctly.
because you had to show a message to user that user can't give a name which has (\) character.
I think the scenario is like:
var user_input_name = document.getElementById('the_name').value;
Then the asker wants to check if user_input_name contains any [\]. If so, then alert the user.
If user enters [aa ///\] in HTML input box, then if you alert(user_input_name), you will see [aaa ///\]. You don't need to escape, i.e. replace [\] to be [\\] in JavaScript code. When you do escaping, that is because you are trying to make of a string which contain special characters in JavaScript source code. If you don't do it, it won't be parsed correct. Since you already get a string, you don't need to pass it into an escaping function. If you do so, I am guessing you are generating another JavaScript code from a JavaScript code, but it's not the case here.
I am guessing asker wants to simulate the input, so we can understand the problem. Unfortunately, asker doesn't understand JavaScript well. Therefore, a syntax error code being supplied to us:
var ttt = "aa ///\";
Hence, we assume the asker having problem with escaping.
If you want to simulate, you code must be valid at first place.
var ttt = "aa ///\\"; // <- This is correct
// var ttt = "aa ///\"; // <- This is not.
alert(ttt); // You will see [aa ///\] in dialog, which is what you expect, right?
Now, you only need to do is
var user_input_name = document.getElementById('the_name').value;
if (user_input_name.indexOf("\\") >= 0) { // There is a [\] in the string
alert("\\ is not allowed to be used!"); // User reads [\ is not allowed to be used]
do_something_else();
}
Edit: I used [] to quote text to be shown, so it would be less confused than using "".
The backslash \ is reserved for use as an escape character in Javascript.
To use a backslash literally you need to use two backslashes
\\
If you want to use special character in javascript variable value, Escape Character (\) is required.
Backslash in your example is special character, too.
So you should do something like this,
var ttt = "aa ///\\\\\\"; // --> ///\\\
or
var ttt = "aa ///\\"; // --> ///\
But Escape Character not require for user input.
When you press / in prompt box or input field then submit, that means single /.
Note: I had to simplify my actual use case to spare SO a lot of backstory. So if your first reaction to this question is: why would you ever do this, trust me, I just need to.
I'm trying to write a Groovy expression that replaces double-quotes (""") that appear in a string with single-quotes ("'").
// BEFORE: Replace my "double" quotes with 'single' quotes.
String toReplace = "Replace my \"double-quotes\" with 'single' quotes.";
// Wrong: compiler error
String replacerExpression = "toReplace.replace(""", "'");";
Binding binding = new Binding();
binding.setVariable("toReplace", toReplace);
GroovyShell shell = new GroovyShell(binding);
// AFTER: Replace my 'double' quotes with 'single' quotes.
String replacedString = (String)shell.evaluate(replacerExpression);
The problem is, I'm getting a compile error on the line where I assign replacerExpression:
Syntax error on token ""toReplace.replace("", { expected
I think it's because I need to escape the string that contains the double-quote character (""") but since it's a string-inside-a-string, I'm not sure how to properly escape it here. Any ideas?
You need to escape the quote within quotes in this line:
String replacerExpression = "toReplace.replace(""", "'");";
The string will be evaluated twice: once as a string literal, and once as a script. This means you have to escape it with a backslash, and escape the backslash too. Also, with the embedded quotes, it'll be much more readable if you use triple quotes.
Try this (in groovy):
String replacerExpression = """toReplace.replace("\\"", "'");""";
In Java, you're stuck with using backslashes to escape all the quotes and the embedded backslash:
String replacerExpression = "toReplace.replace(\"\\\"\", \"\'\");";
Triple-quotes work well, but one can also use single-quoted string to specify a double-quote, and a double-quoted string for a single-quote.
Consider this:
String toReplace = "Replace my \"double-quotes\" with 'single' quotes."
// key line:
String replacerExpression = """toReplace.replace('"', "'");"""
Binding binding = new Binding(); binding.setVariable("toReplace", toReplace)
GroovyShell shell = new GroovyShell(binding)
String replacedString = (String)shell.evaluate(replacerExpression)
That is, after the string literal evaluation, this is evaluated in the Groovy shell:
toReplace.replace('"', "'");
If that is too hard on the eyes, replace the "key line" above with another style (using slashy strings):
String ESC_DOUBLE_QUOTE = /'"'/
String ESC_SINGLE_QUOTE = /"'"/
String replacerExpression = """toReplace.replace(${ESC_DOUBLE_QUOTE}, ${ESC_SINGLE_QUOTE});"""
Please try to use regular expressions to solve this kind of problems, instead of messing your head to tackle the escaping of quotes.
I have put up a solution using groovy console. Please see if that helps.
I want to write a function, to replace all the numbers in a string with literal \d. My code is:
val r = """\d""".r
val s = r.replaceAllIn("123abc", """\d""")
println(s)
I expect the result is \d\d\dabc, but get:
dddabc
Then I change my code (line 2) to:
val s = r.replaceAllIn("123abc", """\\d""")
The result is correct now: \d\d\dabc
But I don't understand why the method replaceAllIn converts the string, not use it directly?
There was a toList in my previous code, that now what I want. I have just update the question. Thanks to everyone.
Just remove the toList.
val r = """\d""".r
val list = r.replaceAllIn("123abc", """\\d""")
println(list)
Strings are (implicitly, via WrappedString, convertible to) Seq[Char]. If you invoke toList, you will have a List[Char].
Scala's Regex uses java.util.regex underneath (at least on the JVM). Now, if you look up replaceAll on Java docs, you'll see this:
Note that backslashes (\) and dollar
signs ($) in the replacement string
may cause the results to be different
than if it were being treated as a
literal replacement string. Dollar
signs may be treated as references to
captured subsequences as described
above, and backslashes are used to
escape literal characters in the
replacement string.