Basics

Question 1

Indicates the start of the expression

Question 2

Indicates the end of the expression

Answer 2

$

Question 3

lowercase characters

Answer 3

[[:lower:]]

Question 4

alphabetical characters

Answer 4

[[:alpha:]]

Question 5

Numbers

Answer 5

[[:digits:]]

Question 6

Punctuation

Answer 6

[[:punct:]]

Question 7

Uppercase

Answer 7

[[:upper:]]

Question 8

Wildcard for 1 character

Answer 8

.

Question 9

Escape character

Answer 9

\

So when you need to search for a period, you’d enter .

Question 10

Wildcard for multiple charcters

Answer 10

*

Question 11

Check for a specific number of characters

Answer 11

{2n}\ for example ‘T.{2}n’

Question 12

Back references

Answer 12

grep ‘(.)(\1)’ this finds any scenario where there are two identical charcters, side by side

Question 13

What is a token

Answer 13

Symbol character that has a specific meaning, rather than purely it’s face value

Question 14

What is a character class

Answer 14

A way to check for a specific set of characters

Question 15

whitespace

Answer 15

[[:space:]]

Question 16

What happens if grep encounters an error

Answer 16

It throws a message to the console

Question 17

What happens it grep matches a pattern

Answer 17

It prints out the matching line

Question 18

What happens if grep doesn’t find a match

Answer 18

It returns to the command prompt

Question 19

spaces (either spaces or tabs)

Answer 19

[[:space:]]

Question 20

What is a character literal

Answer 20

The charcter’s face or symbol is what it means. There is no other possible meaning.

This comes up in regular expressions because sometimes we can use symbols to indicate special patterns. If we want to search for the specific symbol instead of the pattern, we need to adjust how we search for it.

Question 21

What is considered a word

Answer 21

Characters with whitespace or special charcters on either side. The whitespace and special characters indicate the word boundaries (Where a word begins and ends).

Question 22

tab character

Answer 22

\t