Why file I/O is core to scripting in Bash Scripting - Challenge Your Understanding

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this file read command?

Consider a file named data.txt containing the lines:

apple
banana
cherry

What will the following command output?

head -n 2 data.txt

Bash Scripting

head -n 2 data.txt

A cherry

B

banana
cherry

C

apple
banana
cherry

D

apple
banana

💡 Hint

The head command shows the first lines of a file.

The head -n 2 command outputs the first two lines of the file, which are 'apple' and 'banana'.

💻 Command Output

intermediate

What does this file write command do?

What is the result of running this command?

echo "Hello World" > greetings.txt

Assuming greetings.txt did not exist before.

Bash Scripting

echo "Hello World" > greetings.txt

A Deletes greetings.txt if it exists

B Creates greetings.txt with content 'Hello World'

C Appends 'Hello World' to greetings.txt if it exists

D Prints 'Hello World' to the terminal only

💡 Hint

The single > operator writes to a file, creating or overwriting it.

The command creates the file greetings.txt and writes 'Hello World' inside it, overwriting if the file existed.

📝 Syntax

advanced

Which command correctly appends text to a file?

You want to add the line 'Goodbye' to the end of farewell.txt without deleting existing content. Which command does this?

A echo "Goodbye" >> farewell.txt

B echo "Goodbye" < farewell.txt

C echo "Goodbye" | farewell.txt

D echo "Goodbye" > farewell.txt

💡 Hint

Use the operator that adds to the file instead of replacing it.

The double >> operator appends text to the file, preserving existing content.

🔧 Debug

advanced

Why does this script fail to read the file?

This script tries to read notes.txt but prints nothing:

while read line; do
  echo $line
done < notes.txt

What is the problem?

Bash Scripting

while read line; do
  echo $line
done < notes.txt

A The file redirection should be after done, not before

B The variable $line is not quoted, causing issues with spaces

C The file notes.txt does not exist or is empty

D The read command needs -r option to work

💡 Hint

Check if the file exists and has content.

If notes.txt is missing or empty, the loop reads nothing and prints nothing.

🚀 Application

expert

How many lines will this script output?

Given a file log.txt with 100 lines, what is the number of lines output by this script?

count=0
while IFS= read -r line; do
  if [[ $line == *ERROR* ]]; then
    echo "$line"
    ((count++))
  fi
done < log.txt
echo $count

Bash Scripting

count=0
while IFS= read -r line; do
  if [[ $line == *ERROR* ]]; then
    echo "$line"
    ((count++))
  fi
done < log.txt
echo $count

A The number of lines containing 'ERROR' plus one

B The number of lines containing 'ERROR'

C 100 lines

D Zero lines

💡 Hint

The script prints lines with 'ERROR' and then prints the count of those lines.

The script outputs each line containing 'ERROR' and then prints the total count of such lines on a separate line, resulting in the number of lines containing 'ERROR' plus one.