Regex for parsing directory and filename

Question

I m trying to write a regex that will parse out the directory and filename of a fully qualified path using matching groups   so      var log xyz 10032008 log   would recognize group 1 to be   var log xyz  and group 2 to be  10032008 log   Seems simple but I can t get the matching groups to work for the life of me   NOTE   As pointed out by some of the respondents this is probably not a good use of regular expressions   Generally I d prefer to use the file API of the language I was using   What I m actually trying to do is a little more complicated than this but would have been much more difficult to explain  so I chose a domain that everyone would be familiar with in order to most succinctly describe the root problem

User · Answer

What about this       0 1                      Deterministic                               Strict         0 1

User · Answer

Try this                            It will leave the trailing slash on the path  though

User · Answer

Try this                    EDIT  escaped the forward slash to prevent problems when copy pasting the Regex

User · Answer

What language  and why use regex for this simple task   If you must                    gives you the two parts you wanted  You might need to quote the parentheses                        depending on your preferred language syntax   But I suggest you just use your language s string search function that finds the last     character  and split the string on that index

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A very late answer  but hope this will help            w    log     This uses lazy check for    and I just modified the accepted answer  http   regex101 com r gV2xB7 1

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Reasoning   I did a little research through trial and error method  Found out that all the values that are available in keyboard are eligible to be a file or directory except     in  nux machine    I used touch command to create file for following characters and it created a file       Comma separated values below                                          amp                                   -                                             lt                              It failed only when I tried creating      because it s root directory  and filename container   because it file separator     And it changed the modified time of current dir   when I did touch    However  file log is possible   And of course  a-z  A-Z  0-9  -  hypen      underscore  should work   Outcome  So  by the above reasoning we know that a file name or directory name can contain anything except   forward slash  So  our regex will be derived by what will not be present in the file name directory name         P lt dir gt                        P lt filename gt            Step by Step regexp creation process  Pattern Explanation  Step-1  Start with matching root directory  A directory can start with   when it is absolute path and directory name when it s relative  Hence  look for   with zero or one occurrence      P lt filepath gt   P lt root gt        P lt rest of the path gt           Step-2  Try to find the first directory   Next  a directory and its child is always separated by    And a directory name can be anything except    Let s match  var  first then      P lt filepath gt   P lt first directory gt   P lt root gt                P lt rest of the path gt           Step-3  Get full directory path for the file  Next  let s match all directories     P lt filepath gt   P lt dir gt   P lt root gt        P lt single dir gt             P lt rest of the path gt           Here  single dir is yz  because  first it matched var   then it found next occurrence of same pattern i e  log   then it found the next occurrence of same pattern yz   So  it showed the last occurrence of pattern   Step-4  Match filename and clean up  Now  we know that we re never going to use the groups like single dir  filepath  root  Hence let s clean that up   Let s keep them as groups however don t capture those groups   And rest of the path is just the filename  So  rename it  And a file will not have   in its name  so it s better to keep             P lt dir gt                        P lt filename gt            This brings us to the final result  Of course  there are several other ways you can do it  I am just mentioning one of the ways here     Regex Rules used above are listed here    means string starts with    P lt dir gt pattern  means capture group by group name  We have two groups with group name dir and file     pattern  means don t consider this group or non-capturing group    means match zero or one    means match one or more       means matches any char except forward slash           means if it is absolute path then it can start with   otherwise it won t  So  match zero or one occurrence of             means one or more characters which aren t forward slash     which is followed by a forward slash      This will match var  or xyz   One directory at a time

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In languages that support regular expressions with non-capturing groups                       I ll explain the gnarly regex by exploding it                                              What the parts mean      -- capture group 1 starts        -- non-capturing group starts            -- greedily match as many non-directory separators as possible        -- match a single directory-separator character      -- non-capturing group ends      -- repeat the non-capturing group zero-or-more times    -- capture group 1 ends       -- capture all remaining characters in group 2   Example  To test the regular expression  I used the following Perl script        usr bin perl -w  use strict  use warnings   sub test     my  str   shift    my  testname   shift      str    m                        print   str --  testname n     print    1   1 n     print    2   2 n n      test   var log xyz 10032008 log    absolute path    test  var log xyz 10032008 log    relative path    test  10032008 log    filename-only    test   10032008 log    file directly under root      The output of the script      var log xyz 10032008 log -- absolute path   1   var log xyz    2  10032008 log  var log xyz 10032008 log -- relative path   1  var log xyz    2  10032008 log  10032008 log -- filename-only   1    2  10032008 log   10032008 log -- file directly under root   1      2  10032008 log

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Most languages have path parsing functions that will give you this already  If you have the ability  I d recommend using what comes to you for free out-of-the-box   Assuming   is the path delimiter                      The first group will be whatever the directory path info is  the second will be the filename  For example     foo bar baz log    foo bar   is the path   baz log  is the file foo bar log   foo   is the path   bar log  is the file  foo bar    foo   is the path   bar  is the file  foo bar     foo bar   is the path and there is no file

[regex] Regex for parsing directory and filename

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