Regular Expressions Interview Questions and Answers
Question - 11 : - What is Greedy quantifiers * ,+,? ?.
Answer - 11 : -
Greedy quantifiers trying to match as much as possible.
Question - 12 : - What is Lazy quantifiers *? ,+?,?? ?.
Answer - 12 : -
Non Greedy or lazy quantifiers trying to match as possible minimum to satisfy condition
Question - 13 : - How do you see all text files from your system?
Answer - 13 : -
Go to search type *.txt
meaning of pattern is to select all the files which has extension .txt
Question - 14 : - What is Backreferencing in Regular expressions?
Answer - 14 : -
Backreferencing is a feature of regular expressions, it is used to match new text that is same as matched earlier in the expression.
[0-9]+ match all the digits 9334
([0-9])\1+ match only 9334
\1 represent the match which was matched ([0-9])
Question - 15 : - What is lookaround in Regular expressions?
Answer - 15 : -
Generally regex works left to right but sometimes needs to process the text right to left.
Processing text right to left is called lookaround.
example : Needs to insert coma after three digits in cash
12,345,678
Question - 16 : - How lookaround works in Regular expressions?
Answer - 16 : -
It is working like meta characters [\b][^][$] but they match the text based on positions with in the text.
Question - 17 : - Types of lookaround in Regular expressions?
Answer - 17 : -
we have two types of look around.
1) lookahead
2)lookbehind
Question - 18 : - What is lookahead in Regular expressions?
Answer - 18 : -
It is working towords to the right to see if match is exist
Positive Lookahead:
- If successful match to the right
- positive lookahead is specified with ( ?=...)
- Ex: (?=\d) successful where digit comes right
Negative Lookahead:
- If successful not match to the right
- positive lookahead is specified with ( ?!=...)
Question - 19 : - What is lookbehind in Regular expressions?
Answer - 19 : -
It is working towords to the left to see if match is exist
Positive Lookbehind:
If match is successful match to the left
Positive lookbehind is specified with ( ?<=...)
Ex: (?<=\d) successful where digit comes left
Negative Lookbehind:
If match is successful not match to the left
Negative lookbehind is specified with ( ?
Question - 20 : - What is the meaning "(?" in Regula expressions?
Answer - 20 : -
Open parenthesis sequence , They all begin with two characters like (? always perform some special functionality
(?: ..) : group it but don't capture
(?=...): look ahead
(?<=...) : look behind