grep in scripts in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the grep command do in a script?

grep searches for lines in a file or input that match a given pattern. It helps find specific text quickly.

beginner

How do you use grep to search for the word "apple" in a file named fruits.txt?

Use the command: grep 'apple' fruits.txt. It will show all lines containing "apple".

beginner

What does the -i option do in grep?

The -i option makes the search case-insensitive. It finds matches regardless of uppercase or lowercase letters.

intermediate

How can grep be used in a script to check if a pattern exists and then run a command?

You can use grep with an if statement. For example:<br>if grep -q 'pattern' file.txt; then echo 'Found'; fi<br>This runs the echo only if the pattern is found.

intermediate

What does the -q option do in grep?

The -q option makes grep run quietly. It does not print output but sets the exit status to indicate if a match was found.

What will grep 'dog' pets.txt do?

A Show lines containing 'dog' in pets.txt

B Delete lines containing 'dog' in pets.txt

C Replace 'dog' with 'cat' in pets.txt

D Count the number of lines in pets.txt

grep searches and shows lines matching the pattern. It does not delete or replace text.

Which grep option makes the search ignore case?

A -v

B -i

C -q

D -r

The -i option makes grep ignore case differences.

What does the -q option do in grep?

A Print matching lines

B Search recursively

C Run quietly without output

D Invert match

-q makes grep silent and only sets the exit status.

How can you use grep in a script to run a command only if a pattern is found?

A Use <code>grep -v</code>

B Use <code>grep -i</code>

C Use <code>grep -r</code>

D Use <code>if grep -q 'pattern' file; then ... fi</code>

The if statement with grep -q checks for the pattern quietly and runs commands conditionally.

What will grep -v 'cat' animals.txt do?

A Show lines not containing 'cat'

B Replace 'cat' with another word

C Count lines with 'cat'

D Show lines containing 'cat'

The -v option inverts the match, showing lines that do NOT contain the pattern.

Explain how you would use grep in a bash script to check if a file contains a specific word and then print a message.

Think about using <code>grep -q</code> inside an <code>if</code> condition.

Describe the difference between using grep with and without the -i option.

Consider how 'Apple' and 'apple' are treated.