/(.+)n1/ works but /(.*)n1/ doesn't when they should both work

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP











up vote
0
down vote

favorite












I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.

The following command1:



sed -E '$!N;/(.+)n1/!P;D' <<IN
one
one_more
two
two_more
IN


prints



one_more
two_more


OK, that's the expected output.

Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:



sed -E '$!N;/(.*)n1/!P;D' <<IN
one
one_more
two
two_more
IN


prints just one line



two_more


It appears to work fine in the left hand side of a substitution e.g.



sed -E '$!N;s/(.*)n1/1/' <<IN
one
one_more
two
two_more
IN


prints



one_more
two_more


just not in a context address...

What's going on here ?



1: I'm using ERE for simplicity/readability, the same happens when using BRE






sed regular-expression







share|improve this question

























    up vote
    0
    down vote

    favorite












    I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.

    The following command1:



    sed -E '$!N;/(.+)n1/!P;D' <<IN
    one
    one_more
    two
    two_more
    IN


    prints



    one_more
    two_more


    OK, that's the expected output.

    Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:



    sed -E '$!N;/(.*)n1/!P;D' <<IN
    one
    one_more
    two
    two_more
    IN


    prints just one line



    two_more


    It appears to work fine in the left hand side of a substitution e.g.



    sed -E '$!N;s/(.*)n1/1/' <<IN
    one
    one_more
    two
    two_more
    IN


    prints



    one_more
    two_more


    just not in a context address...

    What's going on here ?



    1: I'm using ERE for simplicity/readability, the same happens when using BRE






    sed regular-expression







    share|improve this question























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.

      The following command1:



      sed -E '$!N;/(.+)n1/!P;D' <<IN
      one
      one_more
      two
      two_more
      IN


      prints



      one_more
      two_more


      OK, that's the expected output.

      Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:



      sed -E '$!N;/(.*)n1/!P;D' <<IN
      one
      one_more
      two
      two_more
      IN


      prints just one line



      two_more


      It appears to work fine in the left hand side of a substitution e.g.



      sed -E '$!N;s/(.*)n1/1/' <<IN
      one
      one_more
      two
      two_more
      IN


      prints



      one_more
      two_more


      just not in a context address...

      What's going on here ?



      1: I'm using ERE for simplicity/readability, the same happens when using BRE






      sed regular-expression







      share|improve this question













      I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.

      The following command1:



      sed -E '$!N;/(.+)n1/!P;D' <<IN
      one
      one_more
      two
      two_more
      IN


      prints



      one_more
      two_more


      OK, that's the expected output.

      Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:



      sed -E '$!N;/(.*)n1/!P;D' <<IN
      one
      one_more
      two
      two_more
      IN


      prints just one line



      two_more


      It appears to work fine in the left hand side of a substitution e.g.



      sed -E '$!N;s/(.*)n1/1/' <<IN
      one
      one_more
      two
      two_more
      IN


      prints



      one_more
      two_more


      just not in a context address...

      What's going on here ?



      1: I'm using ERE for simplicity/readability, the same happens when using BRE






      sed regular-expression




      sed regular-expression






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 41 mins ago









      don_crissti

      48.1k15127157




      48.1k15127157

























          active

          oldest

          votes











          Your Answer







          StackExchange.ready(function()
          var channelOptions =
          tags: "".split(" "),
          id: "106"
          ;
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function()
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled)
          StackExchange.using("snippets", function()
          createEditor();
          );

          else
          createEditor();

          );

          function createEditor()
          StackExchange.prepareEditor(
          heartbeatType: 'answer',
          convertImagesToLinks: false,
          noModals: false,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: null,
          bindNavPrevention: true,
          postfix: "",
          onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          );



          );













           

          draft saved


          draft discarded


















          StackExchange.ready(
          function ()
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f477595%2fn-1-works-but-n-1-doesnt-when-they-should-both-work%23new-answer', 'question_page');

          );

          Post as a guest






















          active

          oldest

          votes













          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes















           

          draft saved


          draft discarded















































           


          draft saved


          draft discarded














          StackExchange.ready(
          function ()
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f477595%2fn-1-works-but-n-1-doesnt-when-they-should-both-work%23new-answer', 'question_page');

          );

          Post as a guest
































































          -

          Popular posts from this blog

          How to check contact read email or not when send email to Individual?

          Image
          Clash Royale CLAN TAG #URR8PPP up vote 1 down vote favorite I'm using WordPress 4.9.8, CiviCRM to 5.5.1, I usually send email to contact by Search> Find contacts View contact details Action> Send email Send email ok, Contact received mail ok like picture But status only Email sent though contact read email or not. So, can CiviCRM can change status to Email read when contact read email? wordpress email share | improve this question asked Sep 26 at 0:12 ToanLuong 49 9 add a comment  |  up vote 1 down vote favorite I'm using WordPress 4.9.8, CiviCRM to 5.5.1, I usually send email to contact by Search> Find contacts View contact details Action> Send email Send email ok, Contact received mail ok like picture But status only Email sent though contact read email or not. So, can CiviCRM can change status to Email read when contact read email? wordpress email share | improve this questi...
          Read more

          Displaying single band from multi-band raster using QGIS

          Image
          Clash Royale CLAN TAG #URR8PPP 1 How can I extract a single band from multi-band raster in QGIS? I have an remote sensed image which has 6 bands (including NDVI band), I want to display each band separately, but have no idea how to do. I have seen some questions similar here but none worked for me. The original image (has 6 bands) is: I want to display the band 6 which should be like this: But I tried gdal_translate, and couldn't get the correct result. What I have got is: qgis raster multi-band share | improve this question edited Mar 5 at 0:53 Summer asked Mar 4 at 6:42 Summer Summer 23 6 Is this any help gis.stackexchange.com/questions/220658/… ? if not gis.stackexchange.com/questions/62133/… might help. – Michael Stimson Mar 4 at 6:46 Thanks for answering but when I used gdal_translate, qgis showed that 'Error 4: Kayena.tif: No such file or directory". Would you know how to fi...
          Read more

          How many registers does an x86_64 CPU actually have?

          Image
          Clash Royale CLAN TAG #URR8PPP up vote 2 down vote favorite I am currently learning reverse engineering and am studying the flags register. I had in my mind that rflags was just another name for one of the 16 general purpose registers, for example rax or rbx . But it looks like rflags is actually an additional register. So that makes 17 registers in total... how many more could there be? I have spent at least an hour on this and found numerous different answers. The best answer so far is this, which says that there are 40 registers in total. 16 General Purpose Registers 2 Status Registers 6 Code Segment Registers 16 SSE Registers 8 FPU/MMX Registers But if I add that up, I get 48. Could anybody provide an official answer on how many registers an x86_64 CPU has (e.g. an Intel i7). Additionally, I have seen references to 'hardware' and 'architectural' registers. What are those registers and how many are there? register x86-64 share | improve this...
          Read more