Extended regex (grep -E) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to search for lines containing either 'cat' or 'dog' in the file animals.txt using extended regex.

Bash Scripting

grep -E '[1]' animals.txt

Drag options to blanks, or click blank then click option'

Acat|dog

Bcat*dog

Ccat?dog

Dcat.dog

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' which matches any character instead of '|' for OR.

Using '*' or '?' which are quantifiers, not OR operators.

The pipe symbol '|' in extended regex means OR, so 'cat|dog' matches lines with 'cat' or 'dog'.

2fill in blank

medium

Complete the code to find lines starting with 'Error' followed by a space and a number in log.txt using extended regex.

Bash Scripting

grep -E '^[1] [0-9]+' log.txt

Drag options to blanks, or click blank then click option'

AError*

BError

CError?

DError+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' or '+' after 'Error' which changes the meaning.

Using '?' which makes 'Error' optional.

The caret '^' anchors the start of the line, so '^Error ' matches lines starting with 'Error ' exactly.

3fill in blank

hard

Fix the error in the code to match lines containing either 'cat', 'dog', or 'bird' in pets.txt using extended regex.

Bash Scripting

grep -E 'cat[1]dog[2]bird' pets.txt

Drag options to blanks, or click blank then click option'

A|

B.

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' which matches any character instead of OR.

Using '*' or '+' which are quantifiers, not separators.

The '|' symbol is used to separate alternatives in extended regex, so 'cat|dog|bird' matches any of these words.

4fill in blank

hard

Fill both blanks to create a pattern that matches lines with a word starting with 'a' followed by one or more digits in data.txt.

Bash Scripting

grep -E '[1][0-9][2]' data.txt

Drag options to blanks, or click blank then click option'

Aa+

B+

Da

Attempts:

3 left

💡 Hint

Common Mistakes

Putting '+' after 'a' which means one or more 'a's, not digits.

Not using '+' after digits, so only one digit matches.

The pattern 'a[0-9]+' matches 'a' followed by one or more digits. The '+' after [0-9] means one or more digits.

5fill in blank

hard

Fill all three blanks to create a pattern that matches lines containing either 'cat', 'dog', or 'bird' followed by a space and a number in pets.txt.

Bash Scripting

grep -E '[1][2][3] [0-9]+' pets.txt

Drag options to blanks, or click blank then click option'

Acat

B|

Cdog|bird

Dbird

Attempts:

3 left

💡 Hint

Common Mistakes

Putting all animals in one option without '|'.

Missing the space before the number.

The pattern 'cat|dog|bird [0-9]+' matches any of the three words followed by a space and one or more digits.