regex period - match any one character

Anywhere you add a . (period) in your expression it will match any character in that spot.

Example 1:

$ grep 'c.t' file.txt
cat
cut
c1t
(implicit class)
cst
cpt
Location
simplification

From the example it won't match ct - it must have one character, and for 'c..t' - they should be 2 characters.