CODEWITHSUNDEEP
javaregexparsingre2sumologic
Peter
Peter

Reputation: 448

Regex for partial path

I have paths like these (single lines):

/
/abc
/def/
/ghi/jkl
/mno/pqr/
/stu/vwx/yz
/abc/def/ghi/jkl

I just need patterns that match up to the third "/". In other words, paths containing just "/" and up to the first 2 directories. However, some of my directories end with a "/" and some don't. So the result I want is:

/
/abc
/def/
/ghi/jkl
/mno/pqr/
/stu/vwx/
/abc/def/

So far, I've tried (\/|.*\/) but this doesn't get the path ending without a "/".

Upvotes: 2

Views: 22738

Answers (4)

user10571144
user10571144

Reputation: 34

^(/([^/]+){0,2}\/?)$

To break it down

  • ^ is the start of the string

  • {0,2} means repeat the previous between 0 and 2 times.

  • Then it ends with an optional slash by using a ?

  • String end is $ so it doesn't match longer strings.

  • () Around the whole thing to capture it.

But I'll point out that the is almost always the wrong answer for directory matching. Some directories have special meaning, like /../.. which actually goes up two directories, not down. Better to use the systems directory API instead for more robust results.

Upvotes: 1

The fourth bird
The fourth bird

Reputation: 163207

Your regex (\/|.*\/) uses an alternation which matches either a forward slash or any characters 0+ times greedy followed by matching a forward slash.

So in for example /ghi/jkl, the first match will be the first forward slash. Then this part .* of the next pattern will match from the first g until the end of the string. The engine will backtrack to last forward slash to fullfill the whole .*\/ pattern.

The trailing jkl can not be matched anymore by neither patterns of the alternation.

Note that you don't have to escape the forward slash.

You could use:

^/(?:\w+/?){0,2}$

In Java:

String regex = "^/(?:\\w+/?){0,2}$";

Regex demo

Explanation

  • ^ Start of the string
  • / Match forward slash
  • (?: Non capturing group
    • \w+ Match 1+ word characters (If you want to match more than \w you could use a character class and add to that what you want match)
    • /? Match optional forward slash
  • ){0,2} Close non capturing group and repeat 0 - 2 times
  • $ End of the string

Upvotes: 2

azro
azro

Reputation: 54148

You need a pattern like ^(\/\w+){0,2}\/?$, it checks that you have (/ and name) no more than 2 times and that it can end with /

Details :

  • ^ : beginning of the string
  • (\/\w+) : slash (escaped) and word-char, all in a group
  • {0,2} the group can be 0/1/2 times
  • \/? : slash (escaped) can be 0 or 1 time

Online DEMO Regex DEMO

Upvotes: 2

slartidan
slartidan

Reputation: 21566

I would recommend this pattern:

/^(\/[^\/]+){0,2}\/?$/gm

DEMO

It works like this:

  • ^ searches for the beginning of a line
  • (\/[^\/]+) searches for a path element
    • ( starts a group
    • \/ searches for a slash
    • [^\/]+ searches for some non-slash characters
  • {0,2} says, that 0 to 2 of those path elements should be found
  • \/? allows trailling slashes
  • $ searches for the end of the line

Use these modifiers:

  • g to search for several matches within the input
  • m to treat every line as a separate input

Upvotes: 5

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