Mixing
How to replace stuff between two flag symbols using regex
-1
For example I have below text
some {}} outside, and some inside $aa{bb}cc{{dd}ee}ff$, and some more $aa{bb}cc{{dd}ee}ff$ here.
I call $ flag symbol, and now I want to replace all { or } between pairs of $...$ using regex.
The only way I can think of is to replace multiple times, using regex
($.*?)({|})
each time it replaces a { or } inside $...$. After enough time of replacement, we got
some {}} outside, and some inside $aabbccddeeff$, and some more
$aabbccddeeff$ here.
The drawback is that you don't know how many times it needs to get { or } completely replaced, and it apparently not efficient at all.
So I am wondering, is regex capable to doing this in a single run? For regex flavor I mean perl compatible. But if perl can not do this, I would love to know if other regex flavor can do.
regex pcre
edited Jan 1 at 4:45
Charles Duffy
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
add a comment |
-1
For example I have below text
some {}} outside, and some inside $aa{bb}cc{{dd}ee}ff$, and some more $aa{bb}cc{{dd}ee}ff$ here.
I call $ flag symbol, and now I want to replace all { or } between pairs of $...$ using regex.
The only way I can think of is to replace multiple times, using regex
($.*?)({|})
each time it replaces a { or } inside $...$. After enough time of replacement, we got
some {}} outside, and some inside $aabbccddeeff$, and some more
$aabbccddeeff$ here.
The drawback is that you don't know how many times it needs to get { or } completely replaced, and it apparently not efficient at all.
So I am wondering, is regex capable to doing this in a single run? For regex flavor I mean perl compatible. But if perl can not do this, I would love to know if other regex flavor can do.
regex pcre
edited Jan 1 at 4:45
Charles Duffy
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
1
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41
add a comment |
-1
-1
-1
For example I have below text
some {}} outside, and some inside $aa{bb}cc{{dd}ee}ff$, and some more $aa{bb}cc{{dd}ee}ff$ here.
I call $ flag symbol, and now I want to replace all { or } between pairs of $...$ using regex.
The only way I can think of is to replace multiple times, using regex
($.*?)({|})
each time it replaces a { or } inside $...$. After enough time of replacement, we got
some {}} outside, and some inside $aabbccddeeff$, and some more
$aabbccddeeff$ here.
The drawback is that you don't know how many times it needs to get { or } completely replaced, and it apparently not efficient at all.
So I am wondering, is regex capable to doing this in a single run? For regex flavor I mean perl compatible. But if perl can not do this, I would love to know if other regex flavor can do.
regex pcre
edited Jan 1 at 4:45
Charles Duffy
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
For example I have below text
some {}} outside, and some inside $aa{bb}cc{{dd}ee}ff$, and some more $aa{bb}cc{{dd}ee}ff$ here.
I call $ flag symbol, and now I want to replace all { or } between pairs of $...$ using regex.
The only way I can think of is to replace multiple times, using regex
($.*?)({|})
each time it replaces a { or } inside $...$. After enough time of replacement, we got
some {}} outside, and some inside $aabbccddeeff$, and some more
$aabbccddeeff$ here.
The drawback is that you don't know how many times it needs to get { or } completely replaced, and it apparently not efficient at all.
So I am wondering, is regex capable to doing this in a single run? For regex flavor I mean perl compatible. But if perl can not do this, I would love to know if other regex flavor can do.
regex pcre
regex pcre
edited Jan 1 at 4:45
Charles Duffy
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
edited Jan 1 at 4:45
Charles Duffy
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
edited Jan 1 at 4:45
Charles Duffy
178k25201256
edited Jan 1 at 4:45
Charles Duffy
178k25201256
edited Jan 1 at 4:45
Charles Duffy
178k25201256
178k25201256
asked Jan 1 at 4:26
user15964user15964
790824
asked Jan 1 at 4:26
user15964user15964
790824
asked Jan 1 at 4:26
user15964user15964
790824
790824
1
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41
add a comment |
1
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41
1
1
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41
add a comment |
1 Answer
1
active
oldest
votes
1
Try this regex:
[{}](?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)
Click for Demo
Replace each match with a blank string.
Explanation:
[{}]- matches either{or}
(?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)- positive lookahead to make sure that the above match is followed by odd number of$somewhere later in the string. This would make sure that{or}is followed by 1 or 3 or 5 or 7... instances of$somewhere later in the string.
answered Jan 1 at 4:40
PotatoPotato
7,67821133
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this ((?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).
– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like[{}](?=[^$]*$(([^$]*$){2})*[^$]*$)also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2
– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
add a comment |
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1 Answer
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1 Answer
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votes
1
Try this regex:
[{}](?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)
Click for Demo
Replace each match with a blank string.
Explanation:
[{}]- matches either{or}
(?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)- positive lookahead to make sure that the above match is followed by odd number of$somewhere later in the string. This would make sure that{or}is followed by 1 or 3 or 5 or 7... instances of$somewhere later in the string.
answered Jan 1 at 4:40
PotatoPotato
7,67821133
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this ((?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).
– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like[{}](?=[^$]*$(([^$]*$){2})*[^$]*$)also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2
– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
add a comment |
1
Try this regex:
[{}](?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)
Click for Demo
Replace each match with a blank string.
Explanation:
[{}]- matches either{or}
(?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)- positive lookahead to make sure that the above match is followed by odd number of$somewhere later in the string. This would make sure that{or}is followed by 1 or 3 or 5 or 7... instances of$somewhere later in the string.
answered Jan 1 at 4:40
PotatoPotato
7,67821133
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this ((?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).
– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like[{}](?=[^$]*$(([^$]*$){2})*[^$]*$)also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2
– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
add a comment |
1
1
1
Try this regex:
[{}](?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)
Click for Demo
Replace each match with a blank string.
Explanation:
[{}]- matches either{or}
(?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)- positive lookahead to make sure that the above match is followed by odd number of$somewhere later in the string. This would make sure that{or}is followed by 1 or 3 or 5 or 7... instances of$somewhere later in the string.
answered Jan 1 at 4:40
PotatoPotato
7,67821133
Try this regex:
[{}](?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)
Click for Demo
Replace each match with a blank string.
Explanation:
[{}]- matches either{or}
(?=[^$]*$(?:(?:[^$]*$){2})*[^$]*$)- positive lookahead to make sure that the above match is followed by odd number of$somewhere later in the string. This would make sure that{or}is followed by 1 or 3 or 5 or 7... instances of$somewhere later in the string.
answered Jan 1 at 4:40
PotatoPotato
7,67821133
edited Jan 1 at 4:46
answered Jan 1 at 4:40
PotatoPotato
7,67821133
answered Jan 1 at 4:40
PotatoPotato
7,67821133
answered Jan 1 at 4:40
PotatoPotato
7,67821133
7,67821133
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this ((?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).
– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like[{}](?=[^$]*$(([^$]*$){2})*[^$]*$)also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2
– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
add a comment |
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this ((?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).
– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like[{}](?=[^$]*$(([^$]*$){2})*[^$]*$)also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2
– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
1
1
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this (
(?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).– Charles Duffy
Jan 1 at 4:42
Definitely not generic to all regex variants. Has the OP indicated that they have PCRE extensions available? Much of this (
(?:...)) doesn't work even in POSIX ERE, much less BRE; and even some modern engines intentionally don't support lookahead/lookbehind (since those features have serious impact on worst-case performance).– Charles Duffy
Jan 1 at 4:42
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
OP has mentioned that Perl compatible regex is required.
– Potato
Jan 1 at 4:44
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
So they have; adding that to the question's tagging.
– Charles Duffy
Jan 1 at 4:45
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like
[{}](?=[^$]*$(([^$]*$){2})*[^$]*$) also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2– user15964
Jan 1 at 6:51
Thank you so much! Your trick is so clever. There remains one thing I am not sure. Why we have to use non capture group? I found simply use capture group like
[{}](?=[^$]*$(([^$]*$){2})*[^$]*$) also give the same result. But the highlight is somewhat different on regex101.com. See regex101.com/r/nkgjPn/2– user15964
Jan 1 at 6:51
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
Yes you can remove the non-capturing group. In that case, whatever is matched by the regex pattern inside the parenthesis, will be captured in a Group. Refer THIS to know more about Regex Groups.
– Potato
Jan 1 at 7:53
add a comment |
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1
What language are you implementing this in? Can you post an example expected output for your input there?
– CertainPerformance
Jan 1 at 4:27
Hi ,@CertainPerformance I updated my post
– user15964
Jan 1 at 4:33
regexes don't by the themselves support any kind of replacement, modification, etc -- matching is the only thing they do. So you need more tags for whatever tool or layer you're adding that supports making changes.
– Charles Duffy
Jan 1 at 4:41