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New question As suggested by Asaph in previous question: Regex to check if exact string exists
I am looking for a way to check if an exact string match exists in another string using Regex or any better method suggested. I understand that you tell regex to match a space or any other non-word character at the beginning or end of a string. However, I don't know exactly how to set it up.
Search String: #t
Should Match:
String 1: Hello World, Nice to see you! #t
String 2: #T Hello World, Nice to see you!
String 3: Hello World, #t Nice to see you!
Should not Match:
String 1: Hello World, Nice to see you!
String 2: Hello World, Nice to see you! #ta
String 3: #tHello World, Nice to see you!
Edit 2: Added more string samples
Edit 1 for Serg555 and SilentGhost:
Characters allowed in search string:#[_a-zA-Z0-9]# is optional.
Requirements: Search String may be at any character position in the Subject. There may or may not be a white-space character before or after it. I do not want it to match if it is part of another string; such as part of a word.
For the sake of this question: I think I would do this using this pattern: /\b\#t\b/gi
However, this is not returning the results as I would have expected.
I am able to find the exact matches for normal strings (strings where # isn't present) using:
/\b{$search_string}\b/gi
Additional info: this will be used in PHP 5
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You need to use an “escape” to tell the regular expression you want to match it exactly, not use its special behaviour. Like strings, regexps use the backslash, \ , to escape special behaviour. So to match an . , you need the regexp \. .
$ means "Match the end of the string" (the position after the last character in the string).
Basically (0+1)* mathes any sequence of ones and zeroes. So, in your example (0+1)*1(0+1)* should match any sequence that has 1. It would not match 000 , but it would match 010 , 1 , 111 etc. (0+1) means 0 OR 1.
All you need is:
/(?:^|\s)#t\b/i #t is in the beginning or preceded by space.
\b matches word border, which is a border between word-characters and non-word characters. # is a non-word character, therefore your regex matches only strings like this: abc#t, or ab_#t.
Also, normally # is not a special character in regex, you don't need to escape it.
ETA: Your requirements are rather ambiguous: There may or may not be a white-space character before or after it. I do not want it to match if it is part of another string; such as part of a word.
I think you need to give a comprehensive sample of your possible input strings. Because, as it is my regex works just fine.
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