Regular expression with $> symbol - regex

Question

/\/\*[ \t]*\./ /import/i /[ \t\w\/\.\=\-;\[\]\$>"']+\*\/[ \t]*[\n\r]{1,2}/
In the above regular expression, I don't know the meaning of [ \t\w\/\.\=\-;\[\]\$>"']+
which type of data syntax its going to handle.
Can any one please explain me with an example data?

Answer 1

Your characters are inside a Character Class, which means..
[ \t\w\/\.\=\-;\[\]\$>"']+
Any character of:
' ', \t (tab)
word characters (a-z, A-Z, 0-9, _)
\/, \., \=, \-, ;, \[, \], \$, >, ", '
(1 or more times)
In a regular expression characters that are to be interpreted literally rather than as metacharacters can be escaped by preceding them with a backslash symbol (\). Therefore, If you want to use any of these characters as a literal in a regular expression, you need to escape them with a backslash.
For PCRE, and most other Perl-compatible flavors, escape these inside of character classes:
^]\-
And escape these outside of character classes:
^.*+?$|()[{\
Note: The hyphen does not necessarily need escaped if it's considered the first or last character of range inside of the character class.
So basically, this could be simplified to the following.
[ \t\w\/.=;[\]$>"'-]+

Answer 2

To escape a character means to not use its common role, but its special role (if it has one).
For example, the common role for the letter "w" is a simple character "w" inside or outside a character class.
If the character "w" is escaped by putting a \ character before it, \w will have a special role and means any "word" character (letters, digits and _ character) inside or outside a character class.
The common role for the character "]" is not the simple character "]", but it has the role of ending a character class.
If the character "]" is escaped by placing a \ before it, ] will have a special role and it will mean this time a simple "]" character inside or outside a character class.
Outside a character class some characters like "$", "*", "?", "+" have another role than their simple character values, so when you want to specify a plus sign symbol for example, you need to escape it using + because otherwise its common role will be to mean "the previous character one or more times".
Inside a character class however, some of the characters are always used as common characters, so they don't need to be escaped. So for example you don't need to use \= * + \? inside a character class, but only = * + ?.
Inside a character class you need to escape however some characters like "]" because otherwise it will mean the end of the character class.
You also need to escape the character "-" because otherwise it will not be treated as a simple dash, but it will create a range between previous and next characters.
The alternative is to always place the "-" character as the first or the last character in the character class, and in that case it doesn't need to be escaped.
It may look to be complicated, but actually it is not.
You need to think logicly. What happends if you don't escape the "+" character when it appears in a character class? Can it mean that the previous character may appear once or for more times? It wouldn't have any sense such a thing in a character class, so you don't need to escape it. The "=" character don't have any special role insider or outside a character class, so you don't need to escape it either.
The simple dot "." outside a character class means any character but not \n unless the /s modifier is used), but in a character class its common meaning is to act as a simple dot (.) so you don't need to escape it either.
These are not all details regarding the common and special meanings of all characters but I gave them only as examples to show what escaping means.