Regex for quoted string with escaping quotes

Question

How do I get the substring   It s big   problem    using a regular expression   s     function     return   It  s big   problem

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Taken straight from man perlre on a Linux system with Perl 5 22 0 installed  As an optimization  this regex uses the  posessive  form of both   and   to prevent backtracking  for it is known beforehand that a string without a closing quote wouldn t match in any case

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A more extensive version of https   stackoverflow com a 10786066 1794894            50                            50                               50                           This version also contains   Minimum quote length of 50 Extra type of quotes  open     and close

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Messed around at regexpal and ended up with this regex   Don t ask me how it works  I barely understand even tho I wrote it lol

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lt             1 is   should work with any quoted string

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If your IDE is IntelliJ Idea  you can forget all these headaches and store your regex into a String variable and as you copy-paste it inside the double-quote it will automatically change to a regex acceptable format  example in Java  String s    quot   quot en usa  quot             quot    now you can use this variable in your regexp or anywhere

User · Answer

I faced a similar problem trying to remove quoted strings that may interfere with parsing of some files   I ended up with a two-step solution that beats any convoluted regex you can come up with    line   line replace                  Replace escaped quotes with something easier to handle  line   line replaceAll                   x         Simple is beautiful   Easier to read and probably more efficient

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This one works perfect on PCRE and does not fall with StackOverflow                               Explanation    Every quoted string starts with Char      It may contain any number of any characters       Lazy match   ending with non escape character        Statement  2  is Lazy    optional because string can be empty      So               Finally  every quoted string ends with Char     but it can be preceded with even number of escape sign pairs          and it is Greedy    optional               Greedy matching   bacause string can be empty or without ending pairs

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This one works perfect on PCRE and does not fall with StackOverflow                               Explanation    Every quoted string starts with Char      It may contain any number of any characters       Lazy match   ending with non escape character        Statement  2  is Lazy    optional because string can be empty      So               Finally  every quoted string ends with Char     but it can be preceded with even number of escape sign pairs          and it is Greedy    optional               Greedy matching   bacause string can be empty or without ending pairs

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One has to remember that regexps aren t a silver bullet for everything string-y  Some stuff are simpler to do with a cursor and linear  manual  seeking  A CFL would do the trick pretty trivially  but there aren t many CFL implementations  afaik

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Most of the solutions provided here use alternative repetition paths i e   A B     You may encounter stack overflows on large inputs since some pattern compiler implements this using recursion   Java for instance  http   bugs java com bugdatabase view bug do bug id 6337993  Something like this                          or the one provided by Guy Bedford will reduce the amount of parsing steps avoiding most stack overflows

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An option that has not been touched on before is    Reverse the string  Perform the matching on the reversed string  Re-reverse the matched strings    This has the added bonus of being able to correctly match escaped open tags   Lets say you had the following string  String   this  should  NOT match   and  this   should   match  Here    this  should  NOT match   should not be matched and  should  should be  On top of that this   should   match should be matched and   should   should not   First an example       The input string  const myString    String    this  should  NOT match    and  this    should    match        The RegExp  const regExp   new RegExp         Match close                          2                                                Match escaped close quote               1             2                                     Match everything thats not the close quote                  1              0              Match open         1              2                            g         Reverse the matched strings  matches   myString        Reverse the string       split     reverse   join              hctam   dluohs   siht  dna   hctam TON  dluohs  siht   gnirtS          Match the quoted      match regExp            hctam   dluohs   siht      dluohs            Reverse the matches      map x   gt  x split     reverse   join                this   should   match      should            Re order the matches      reverse              should      this   should   match      Okay  now to explain the RegExp  This is the regexp can be easily broken into three pieces  As follows      Part 1                  Match a closing quotation mark   or                    As long as it s not followed by           2      A pair of escape characters                  and a single escape                  As long as that s not followed by an escape     Part 2                 Match inside the quotes                 Match option 1     1            Match the closing quote                 As long as it s followed by                 A pair of escape characters                                  As long as that s not followed by an escape                 and a single escape                 OR                 Match option 2        1         Any character that isn t the closing quote                   Match the group 0 or more times   Part 3   1              Match an open quotation mark that is the same as the closing one                  As long as it s not followed by           2      A pair of escape characters                  and a single escape                  As long as that s not followed by an escape     This is probably a lot clearer in image form  generated using Jex s Regulex  Image on github  JavaScript Regular Expression Visualizer   Sorry  I don t have a high enough reputation to include images  so  it s just a link for now   Here is a gist of an example function using this concept that s a little more advanced  https   gist github com scagood bd99371c072d49a4fee29d193252f5fc file-matchquotes-js

User · Answer

Taken straight from man perlre on a Linux system with Perl 5 22 0 installed  As an optimization  this regex uses the  posessive  form of both   and   to prevent backtracking  for it is known beforehand that a string without a closing quote wouldn t match in any case

User · Answer

Works in The Regex Coach and PCRE Workbench   Example of test in JavaScript    x000D   x000D      var s     function    return   Is big    problem       no         x000D      var m   s match                       x000D      if  m    null  x000D          alert m   x000D   x000D   x000D

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As provided by ePharaoh  the answer is                               To have the above apply to either single quoted or double quoted strings  use

User · Answer

One has to remember that regexps aren t a silver bullet for everything string-y  Some stuff are simpler to do with a cursor and linear  manual  seeking  A CFL would do the trick pretty trivially  but there aren t many CFL implementations  afaik

User · Answer

here is one that work with both   and   and you easily add others at the start              1    1     1  it uses the backreference   1  match exactley what is in the first group    or       http   www regular-expressions info backref html

User · Answer

lt             1 is   should work with any quoted string

User · Answer

Works in The Regex Coach and PCRE Workbench   Example of test in JavaScript    x000D   x000D      var s     function    return   Is big    problem       no         x000D      var m   s match                       x000D      if  m    null  x000D          alert m   x000D   x000D   x000D

User · Answer

This one comes from nanorc sample available in many linux distros   It is used for syntax highlighting of C style strings

User · Answer

If your IDE is IntelliJ Idea  you can forget all these headaches and store your regex into a String variable and as you copy-paste it inside the double-quote it will automatically change to a regex acceptable format  example in Java  String s    quot   quot en usa  quot             quot    now you can use this variable in your regexp or anywhere

User · Answer

I faced a similar problem trying to remove quoted strings that may interfere with parsing of some files   I ended up with a two-step solution that beats any convoluted regex you can come up with    line   line replace                  Replace escaped quotes with something easier to handle  line   line replaceAll                   x         Simple is beautiful   Easier to read and probably more efficient

User · Answer

If it is searched from the beginning  maybe this can work

User · Answer

A more extensive version of https   stackoverflow com a 10786066 1794894            50                            50                               50                           This version also contains   Minimum quote length of 50 Extra type of quotes  open     and close

User · Answer

If it is searched from the beginning  maybe this can work

User · Answer

lt             1 is   should work with any quoted string

User · Answer

One has to remember that regexps aren t a silver bullet for everything string-y  Some stuff are simpler to do with a cursor and linear  manual  seeking  A CFL would do the trick pretty trivially  but there aren t many CFL implementations  afaik

User · Answer

Messed around at regexpal and ended up with this regex   Don t ask me how it works  I barely understand even tho I wrote it lol

User · Answer

Works in The Regex Coach and PCRE Workbench   Example of test in JavaScript    x000D   x000D      var s     function    return   Is big    problem       no         x000D      var m   s match                       x000D      if  m    null  x000D          alert m   x000D   x000D   x000D

User · Answer

One has to remember that regexps aren t a silver bullet for everything string-y  Some stuff are simpler to do with a cursor and linear  manual  seeking  A CFL would do the trick pretty trivially  but there aren t many CFL implementations  afaik

User · Answer

As provided by ePharaoh  the answer is                               To have the above apply to either single quoted or double quoted strings  use

User · Answer

Alternating the    and the   passes over escaped quotes while the lazy quantifier    ensures that you don t go past the end of the quoted string  Works with  NET Framework RE classes

User · Answer

Most of the solutions provided here use alternative repetition paths i e   A B     You may encounter stack overflows on large inputs since some pattern compiler implements this using recursion   Java for instance  http   bugs java com bugdatabase view bug do bug id 6337993  Something like this                          or the one provided by Guy Bedford will reduce the amount of parsing steps avoiding most stack overflows

User · Answer

Works in The Regex Coach and PCRE Workbench   Example of test in JavaScript    x000D   x000D      var s     function    return   Is big    problem       no         x000D      var m   s match                       x000D      if  m    null  x000D          alert m   x000D   x000D   x000D

User · Answer

here is one that work with both   and   and you easily add others at the start              1    1     1  it uses the backreference   1  match exactley what is in the first group    or       http   www regular-expressions info backref html

User · Answer

This one comes from nanorc sample available in many linux distros   It is used for syntax highlighting of C style strings

User · Answer

Alternating the    and the   passes over escaped quotes while the lazy quantifier    ensures that you don t go past the end of the quoted string  Works with  NET Framework RE classes

User · Answer

lt             1 is   should work with any quoted string

User · Answer

An option that has not been touched on before is    Reverse the string  Perform the matching on the reversed string  Re-reverse the matched strings    This has the added bonus of being able to correctly match escaped open tags   Lets say you had the following string  String   this  should  NOT match   and  this   should   match  Here    this  should  NOT match   should not be matched and  should  should be  On top of that this   should   match should be matched and   should   should not   First an example       The input string  const myString    String    this  should  NOT match    and  this    should    match        The RegExp  const regExp   new RegExp         Match close                          2                                                Match escaped close quote               1             2                                     Match everything thats not the close quote                  1              0              Match open         1              2                            g         Reverse the matched strings  matches   myString        Reverse the string       split     reverse   join              hctam   dluohs   siht  dna   hctam TON  dluohs  siht   gnirtS          Match the quoted      match regExp            hctam   dluohs   siht      dluohs            Reverse the matches      map x   gt  x split     reverse   join                this   should   match      should            Re order the matches      reverse              should      this   should   match      Okay  now to explain the RegExp  This is the regexp can be easily broken into three pieces  As follows      Part 1                  Match a closing quotation mark   or                    As long as it s not followed by           2      A pair of escape characters                  and a single escape                  As long as that s not followed by an escape     Part 2                 Match inside the quotes                 Match option 1     1            Match the closing quote                 As long as it s followed by                 A pair of escape characters                                  As long as that s not followed by an escape                 and a single escape                 OR                 Match option 2        1         Any character that isn t the closing quote                   Match the group 0 or more times   Part 3   1              Match an open quotation mark that is the same as the closing one                  As long as it s not followed by           2      A pair of escape characters                  and a single escape                  As long as that s not followed by an escape     This is probably a lot clearer in image form  generated using Jex s Regulex  Image on github  JavaScript Regular Expression Visualizer   Sorry  I don t have a high enough reputation to include images  so  it s just a link for now   Here is a gist of an example function using this concept that s a little more advanced  https   gist github com scagood bd99371c072d49a4fee29d193252f5fc file-matchquotes-js

[regex] Regex for quoted string with escaping quotes

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