I have a regular expression that finds two words in a line.
The problem is that it is case sensitive. I need to edit it so that it matches both the case.
reqular expression
^(.*?(\bPain\b).*?(\bfever\b)[^$]*)$
You can use RegexOptions.Ignorecase to set case insensitive matching mode. This way you make the entire pattern case insensitive. The same effect can be achieved with (?i) inline option at the beginning of the pattern:
(?i)^(.*?(\bPain\b).*?(\bfever\b)[^$]*)$
You can use the inline flag to only set case insensitive mode to part of a pattern:
^(.*?(\b(?i:Pain)\b).*?(\b(?i:fever)\b)[^$]*)$
Or you can just match "pain" or "Pain" with
^(.*?(\b(?i:P)ain\b).*?(\bfever\b)[^$]*)$
Another alternative is using character classes [Pp], etc.
Note that you do not have to set a capturing group round the whole pattern, you will have access to it via rx.Match(str).Groups(0).Value.
^.*?(\b[pP]ain\b).*?(\b[Ff]ever\b)[^$]*$
You can usually set a flag for that, depending on your language, or you can mess up your regex into a more ugly looking one using multiple character classes. [pP][aA][iI][nN] is essentially the word "pain" without it being case sensitive at all.
Well, if you're using VB.net, you can tell the regex object to ignore the case sensitivity when you create it
'Defines the pattern
Dim MyPattern As String = "BlaBla"
'Create a new instance of the regex class with the above pattern
'and the option to ignore the casing
Dim Regex As New Regex(MyPattern, RegexOptions.IgnoreCase)
Related
How can I make the following regex ignore case sensitivity? It should match all the correct characters but ignore whether they are lower or uppercase.
G[a-b].*
Assuming you want the whole regex to ignore case, you should look for the i flag. Nearly all regex engines support it:
/G[a-b].*/i
string.match("G[a-b].*", "i")
Check the documentation for your language/platform/tool to find how the matching modes are specified.
If you want only part of the regex to be case insensitive (as my original answer presumed), then you have two options:
Use the (?i) and [optionally] (?-i) mode modifiers:
(?i)G[a-b](?-i).*
Put all the variations (i.e. lowercase and uppercase) in the regex - useful if mode modifiers are not supported:
[gG][a-bA-B].*
One last note: if you're dealing with Unicode characters besides ASCII, check whether or not your regex engine properly supports them.
Depends on implementation
but I would use
(?i)G[a-b].
VARIATIONS:
(?i) case-insensitive mode ON
(?-i) case-insensitive mode OFF
Modern regex flavors allow you to apply modifiers to only part of the regular expression. If you insert the modifier (?im) in the middle of the regex then the modifier only applies to the part of the regex to the right of the modifier. With these flavors, you can turn off modes by preceding them with a minus sign (?-i).
Description is from the page:
https://www.regular-expressions.info/modifiers.html
regular expression for validate 'abc' ignoring case sensitive
(?i)(abc)
The i flag is normally used for case insensitivity. You don't give a language here, but it'll probably be something like /G[ab].*/i or /(?i)G[ab].*/.
Just for the sake of completeness I wanted to add the solution for regular expressions in C++ with Unicode:
std::tr1::wregex pattern(szPattern, std::tr1::regex_constants::icase);
if (std::tr1::regex_match(szString, pattern))
{
...
}
JavaScript
If you want to make it case insensitive just add i at the end of regex:
'Test'.match(/[A-Z]/gi) //Returns ["T", "e", "s", "t"]
Without i
'Test'.match(/[A-Z]/g) //Returns ["T"]
In JavaScript you should pass the i flag to the RegExp constructor as stated in MDN:
const regex = new RegExp('(abc)', 'i');
regex.test('ABc'); // true
As I discovered from this similar post (ignorecase in AWK), on old versions of awk (such as on vanilla Mac OS X), you may need to use 'tolower($0) ~ /pattern/'.
IGNORECASE or (?i) or /pattern/i will either generate an error or return true for every line.
C#
using System.Text.RegularExpressions;
...
Regex.Match(
input: "Check This String",
pattern: "Regex Pattern",
options: RegexOptions.IgnoreCase)
specifically: options: RegexOptions.IgnoreCase
[gG][aAbB].* probably simples solution if the pattern is not too complicated or long.
Addition to the already-accepted answers:
Grep usage:
Note that for greping it is simply the addition of the -i modifier. Ex: grep -rni regular_expression to search for this 'regular_expression' 'r'ecursively, case 'i'nsensitive, showing line 'n'umbers in the result.
Also, here's a great tool for verifying regular expressions: https://regex101.com/
Ex: See the expression and Explanation in this image.
References:
man pages (man grep)
http://droptips.com/using-grep-and-ignoring-case-case-insensitive-grep
In Java, Regex constructor has
Regex(String pattern, RegexOption option)
So to ignore cases, use
option = RegexOption.IGNORE_CASE
Kotlin:
"G[a-b].*".toRegex(RegexOption.IGNORE_CASE)
You also can lead your initial string, which you are going to check for pattern matching, to lower case. And using in your pattern lower case symbols respectively .
You can practice Regex In Visual Studio and Visual Studio Code using find/replace.
You need to select both Match Case and Regular Expressions for regex expressions with case. Else [A-Z] won't work.enter image description here
In the next search on Vim I would like to ignore the case of the first letter:
/[tlcp]omo
I'd like to know how the case can be ignored for only the first letter of the search pattern.
Vim has the following options to ignore the case in the search pattern:
:set ignorecase
:set smartcase [ignore case if no uppercase in search]
or use \c it at any position in the search pattern:
/hello\c => [find hello and HELLO]
But all of these options ignore the case in the entire pattern, not in part.
One option to ignore the case of a single letter in the search pattern is, using the [] collection of regular expression, to specifically capitalize each letter:
/[tTlLcCpP]omo
But, is there any way to ignore the case in a part of the search pattern without having to specify each and every upper and lower case character using regular expression?
In general, this isn't possible in Vim. The /\c and /\C regexp modifiers unfortunately turn the whole pattern into case (in-)sensitive matching, regardless of where they are placed. (Introducing a new set of modifiers that only work from that position onwards would in my opinion be the best solution.)
Most people usually get around this by using lower/uppercase collections for the insensitive parts, /like [tT][hH][iI][sS]/.
You could also go the opposite route and instead force certain characters to a case (using /\l for lowercase and /\u for uppercase), /\c\%(\l\l\l\l\&like\) this/.
My CmdlineSpecialEdits plugin has (among many others) a CTRL-G c mapping that converts a pattern in the search command-line in such a way that those alphabetic characters between \c...\C become case-insensive matches while the rest remains case-sensitive. In other words, it converts the pattern as if \c and \C would only apply to following atoms, and not the entire pattern.
Example
/My \cfoo\C is \cbad!/
becomes
/My [fF][oO][oO] is [bB][aA][dD]!/
or alternatively
/\c\%(\u\&M\)\%(\l\&y\) foo\%(\l\{2}\&is\) bad!/
How can I make the following regex ignore case sensitivity? It should match all the correct characters but ignore whether they are lower or uppercase.
G[a-b].*
Assuming you want the whole regex to ignore case, you should look for the i flag. Nearly all regex engines support it:
/G[a-b].*/i
string.match("G[a-b].*", "i")
Check the documentation for your language/platform/tool to find how the matching modes are specified.
If you want only part of the regex to be case insensitive (as my original answer presumed), then you have two options:
Use the (?i) and [optionally] (?-i) mode modifiers:
(?i)G[a-b](?-i).*
Put all the variations (i.e. lowercase and uppercase) in the regex - useful if mode modifiers are not supported:
[gG][a-bA-B].*
One last note: if you're dealing with Unicode characters besides ASCII, check whether or not your regex engine properly supports them.
Depends on implementation
but I would use
(?i)G[a-b].
VARIATIONS:
(?i) case-insensitive mode ON
(?-i) case-insensitive mode OFF
Modern regex flavors allow you to apply modifiers to only part of the regular expression. If you insert the modifier (?im) in the middle of the regex then the modifier only applies to the part of the regex to the right of the modifier. With these flavors, you can turn off modes by preceding them with a minus sign (?-i).
Description is from the page:
https://www.regular-expressions.info/modifiers.html
regular expression for validate 'abc' ignoring case sensitive
(?i)(abc)
The i flag is normally used for case insensitivity. You don't give a language here, but it'll probably be something like /G[ab].*/i or /(?i)G[ab].*/.
Just for the sake of completeness I wanted to add the solution for regular expressions in C++ with Unicode:
std::tr1::wregex pattern(szPattern, std::tr1::regex_constants::icase);
if (std::tr1::regex_match(szString, pattern))
{
...
}
JavaScript
If you want to make it case insensitive just add i at the end of regex:
'Test'.match(/[A-Z]/gi) //Returns ["T", "e", "s", "t"]
Without i
'Test'.match(/[A-Z]/g) //Returns ["T"]
In JavaScript you should pass the i flag to the RegExp constructor as stated in MDN:
const regex = new RegExp('(abc)', 'i');
regex.test('ABc'); // true
As I discovered from this similar post (ignorecase in AWK), on old versions of awk (such as on vanilla Mac OS X), you may need to use 'tolower($0) ~ /pattern/'.
IGNORECASE or (?i) or /pattern/i will either generate an error or return true for every line.
C#
using System.Text.RegularExpressions;
...
Regex.Match(
input: "Check This String",
pattern: "Regex Pattern",
options: RegexOptions.IgnoreCase)
specifically: options: RegexOptions.IgnoreCase
[gG][aAbB].* probably simples solution if the pattern is not too complicated or long.
Addition to the already-accepted answers:
Grep usage:
Note that for greping it is simply the addition of the -i modifier. Ex: grep -rni regular_expression to search for this 'regular_expression' 'r'ecursively, case 'i'nsensitive, showing line 'n'umbers in the result.
Also, here's a great tool for verifying regular expressions: https://regex101.com/
Ex: See the expression and Explanation in this image.
References:
man pages (man grep)
http://droptips.com/using-grep-and-ignoring-case-case-insensitive-grep
In Java, Regex constructor has
Regex(String pattern, RegexOption option)
So to ignore cases, use
option = RegexOption.IGNORE_CASE
Kotlin:
"G[a-b].*".toRegex(RegexOption.IGNORE_CASE)
You also can lead your initial string, which you are going to check for pattern matching, to lower case. And using in your pattern lower case symbols respectively .
You can practice Regex In Visual Studio and Visual Studio Code using find/replace.
You need to select both Match Case and Regular Expressions for regex expressions with case. Else [A-Z] won't work.enter image description here
How can I make the following regex ignore case sensitivity? It should match all the correct characters but ignore whether they are lower or uppercase.
G[a-b].*
Assuming you want the whole regex to ignore case, you should look for the i flag. Nearly all regex engines support it:
/G[a-b].*/i
string.match("G[a-b].*", "i")
Check the documentation for your language/platform/tool to find how the matching modes are specified.
If you want only part of the regex to be case insensitive (as my original answer presumed), then you have two options:
Use the (?i) and [optionally] (?-i) mode modifiers:
(?i)G[a-b](?-i).*
Put all the variations (i.e. lowercase and uppercase) in the regex - useful if mode modifiers are not supported:
[gG][a-bA-B].*
One last note: if you're dealing with Unicode characters besides ASCII, check whether or not your regex engine properly supports them.
Depends on implementation
but I would use
(?i)G[a-b].
VARIATIONS:
(?i) case-insensitive mode ON
(?-i) case-insensitive mode OFF
Modern regex flavors allow you to apply modifiers to only part of the regular expression. If you insert the modifier (?im) in the middle of the regex then the modifier only applies to the part of the regex to the right of the modifier. With these flavors, you can turn off modes by preceding them with a minus sign (?-i).
Description is from the page:
https://www.regular-expressions.info/modifiers.html
regular expression for validate 'abc' ignoring case sensitive
(?i)(abc)
The i flag is normally used for case insensitivity. You don't give a language here, but it'll probably be something like /G[ab].*/i or /(?i)G[ab].*/.
Just for the sake of completeness I wanted to add the solution for regular expressions in C++ with Unicode:
std::tr1::wregex pattern(szPattern, std::tr1::regex_constants::icase);
if (std::tr1::regex_match(szString, pattern))
{
...
}
JavaScript
If you want to make it case insensitive just add i at the end of regex:
'Test'.match(/[A-Z]/gi) //Returns ["T", "e", "s", "t"]
Without i
'Test'.match(/[A-Z]/g) //Returns ["T"]
In JavaScript you should pass the i flag to the RegExp constructor as stated in MDN:
const regex = new RegExp('(abc)', 'i');
regex.test('ABc'); // true
As I discovered from this similar post (ignorecase in AWK), on old versions of awk (such as on vanilla Mac OS X), you may need to use 'tolower($0) ~ /pattern/'.
IGNORECASE or (?i) or /pattern/i will either generate an error or return true for every line.
C#
using System.Text.RegularExpressions;
...
Regex.Match(
input: "Check This String",
pattern: "Regex Pattern",
options: RegexOptions.IgnoreCase)
specifically: options: RegexOptions.IgnoreCase
[gG][aAbB].* probably simples solution if the pattern is not too complicated or long.
Addition to the already-accepted answers:
Grep usage:
Note that for greping it is simply the addition of the -i modifier. Ex: grep -rni regular_expression to search for this 'regular_expression' 'r'ecursively, case 'i'nsensitive, showing line 'n'umbers in the result.
Also, here's a great tool for verifying regular expressions: https://regex101.com/
Ex: See the expression and Explanation in this image.
References:
man pages (man grep)
http://droptips.com/using-grep-and-ignoring-case-case-insensitive-grep
In Java, Regex constructor has
Regex(String pattern, RegexOption option)
So to ignore cases, use
option = RegexOption.IGNORE_CASE
Kotlin:
"G[a-b].*".toRegex(RegexOption.IGNORE_CASE)
You also can lead your initial string, which you are going to check for pattern matching, to lower case. And using in your pattern lower case symbols respectively .
You can practice Regex In Visual Studio and Visual Studio Code using find/replace.
You need to select both Match Case and Regular Expressions for regex expressions with case. Else [A-Z] won't work.enter image description here
Thanks to the help with my previous homework question Regex to match tags like <A>, <BB>, <CCC> but not <ABC>, but now I have another homework question.
I need to match tags like <LOL>, <LOLOLOL> (3 uppercase letters, with repeatable last two letters), but not <lol> (need to be uppercase).
Using the technique from the previous homework, I tried <[A-Z]([A-Z][A-Z])\1*>. This works, except there's an additional catch: the repeating part can be in mixed case!
So I need to also match <LOLolol>, <LOLOLOlol>, because it's 3 uppercase letters, with repeatable last two letters in mixed case. I know you can make a pattern case-insensitive with /i, and that will let me match <LOLolol> with the regex I have, but it will also now match <lololol>, because the check for the first 3 letters are also case-insensitive.
So how do I do this? How can I check the first 3 letters case sensitively, and then the rest of the letters case-insensitively? Is this possible with regex?
Yes! You can in fact do this in some flavors, using what is called embedded modifier. This puts the modifier in the pattern, and you can essentially select which parts of the pattern the modifiers apply to.
The embedded modifier for case insensitivity is (?i), so the pattern you want in this case is:
<[A-Z]([A-Z]{2})(?i:\1*)>
References
regular-expressions.info/Modifiers
Specifying Modes Inside The Regular Expression
Instead of /regex/i, you can also do /(?i)regex/
Turning Modes On and Off for Only Part of The Regular Expression
You can also do /first(?i)second(?-i)third/
Modifier Spans
You can also do /first(?i:second)third/