Regex - Search from the end of the string

Question

How do i target something from the end of a string :
complexthing---50 other-_-50 MORE__------50

i want to end up with (50) but this "complexthing--" can end with - so in this case i cant break at " - " from the begging that might make it be confused so the easiest regex for me is to make it get whatever at the end and break at " - "

-(.*)

there is always a - before every 50 to seperate the number and the string, i want to target the number (50)

Answer 1

If I understand you correctly, something like this might work:

-(\d+)$

Match hyphen (-) followed by one or more digits (\d+) just before the end of the string ($). Capture the digits only ( (...) ).

Answer 2

Think about what you're asking for:

• A number which is always at the end of the string
• A number which immediately follows a - character.
• Something which follows a - character, which is not, itself, a - character.

These are all different ways of phrasing your question, getting less-specific as we go. Any of these would probably suit your needs, but I'll cover each case to show how it does what is does.

These can be spelled in a number of different ways. Depending on the regex flavour you're using, some of these ways may need to be escaped differently (for example, X+ vs X\+ vs XX*), and not all may be supported in all flavours.

"A number which is always at the end of the string":

([0-9][0-9]*)$
([0-9]+)$
(\d+)$

Regular expression patterns are greedy, that is: they match as much as they can. So in the first case, asking for at least one number at the end of the string ("at the end of the string" specified as $), will end up giving you the entire number at the end of the string.

"A number which immediately follows a - character":

-([0-9][0-9]*)
-([0-9]+)
-(\d+)

Here, rather than specifying the "end of the string", we specify that it should follow a - character. Because [0-9] will not match a - character itself, we don't need to do anything else to avoid capturing -.

"Something which follows a - character, which is not, itself, a - character":

-([^-][^-]*)
-([^-]+)

This one's a bit trickier: Rather than specifying we want a number, we just specify that we don't want a dash, by specifying a negative match ([^X]). Sometimes it can be tricky to match a - character in a character class, but the rule is "always specify - at the beginning", and you should be fine.