Help with regex pattern

Question

I have a txt file and each line has a set of random strings, I need to select only the lines that contains only the characters: 1234567890qwertyuiopasdfghjklzxcvbnm-._~

I'm reading line by line and verifying char by char, I don't think it's the best way to do that, and I think a RegEx would be perfect.

So can anybody help with with a pattern for this?

thanks!

Answer 1

 /^[-0-9a-z._~]*$/

 ^       :: matches the start of a string/start of a line
 [       :: start of a character class, means match any one of the contained characters
 -       :: dash has a special meaning in character classes, so to avoid having it interpreted for its special meaning, list it first
 0-9     :: shorthand for 0123456789 in a character class
 a-z     :: shorthand for abcdefghijklmnopqrstuvwxyz in a character class
 ._~     :: means exactly these characters in a character class
 ]       :: end of the character class 
 *       :: match zero or more of the previous atom (in this case, the character class)
 $       :: matches the end of a string/end of a line

Answer 2

If I understand you well, you could go with this:

/^([-0-9a-zA-Z._~]\n)+$/

It is case-insensitive, check for end of line and doesn't match an empty line.

Answer 3

It doesn't take much to realize that the regular expression should be equivalent to ^[1234567890qwertyuiopasdfghjklzxcvbnm\-._~]*$. From there you can narrow it down trivially, replacing with 0-9, a-z, etc. . You should learn the basics of regular expressions before using answers you get from others.