Het jokerteken: de punt `.`

The dot . in regex is the wildcard: it matches any single character\u2026 with one important exception: it does NOT match the newline (\n).

Pattern: c.t
Sample:  cat cot cut c@t c\nt
         ^^^ ^^^ ^^^ ^^^

Three letters: a c, any character, a t. No newline in between, so c\nt is not matched (by default).

The dot is extremely useful but also dangerous: used without discipline it captures more than you intended. Combined with the quantifiers in module 2 (.*, .+?) it is the source of 90% of patterns that "don't work the way I expected".

The s flag: "dotAll"

With the s flag (also called dotAll or single-line) the dot matches every character, newline included. Useful to extract blocks that span multiple lines.

Pattern: <p>.*</p>
Flag:    gs
Sample:  <p>prima\nseconda</p>
         ^^^^^^^^^^^^^^^^^^^^^

Limits and behavior of the dot wildcard

The dot . is a powerful wildcard, but by default it does not match newline characters (\\n). If you want the dot to match absolutely everything, including newlines, you must enable the s (dotAll) flag. Be careful when combining the dot with quantifiers (.*), as it tends to consume too much text (greedy behavior).

Try it

Review exercise

Additional challenge