Bash Regular Expressions

Asterisk *:

matches either the string preceding it or the regular expression any time (including 0 times). For example:1122* possible matching strings are:1122,1122222,1123131231 ...

Period.:

matches any one character except for the line break. For example:". ", the string that matches 112+ at least one character may match:1121,1122, 112ABC,1123131231 ..., but does not match 112

Insert Symbol ^:

matches the beginning of a row, but sometimes depends on the context, which may indicate the meaning of a string in a negative regular expression. For example: "^abc" matches only the string with the beginning of ABC

Bash Regular Expressions