Looping over files and directories in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to loop over all files in the current directory.

Bash Scripting

for file in [1]; do echo "$file"; done

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

A~

B.

C/

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' which refers to the current directory itself, not the files inside.

Using '/' which refers to the root directory.

Using '~' which refers to the home directory.

The asterisk (*) matches all files and directories in the current directory.

2fill in blank

medium

Complete the code to loop over all '.txt' files in the 'docs' directory.

Bash Scripting

for file in docs/[1]; do echo "$file"; done

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

A*.txt

B*.doc

Ctxt.*

Ddocs.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*.doc' which matches files with '.doc' extension, not '.txt'.

Using 'txt.*' which is not a valid pattern for '.txt' files.

Using 'docs.txt' which is a filename, not a pattern.

The pattern '*.txt' matches all files ending with '.txt' in the 'docs' directory.

3fill in blank

hard

Fix the error in the code to loop over directories only in the current folder.

Bash Scripting

for dir in [1]; do echo "$dir"; done

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

A*/**

B*/

C.*

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' which matches files and directories.

Using '.*' which matches hidden files and directories.

Using '*/**' which is not a valid pattern in basic bash globbing.

The pattern '*/' matches only directories in the current directory because directories end with a slash.

4fill in blank

hard

Fill both blanks to loop over all '.log' files larger than 1MB in the 'logs' directory.

Bash Scripting

for file in logs/[1]; do if [[ $(stat -c%s "$file") [2] 1048576 ]]; then echo "$file"; fi; done

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

A*.log

B>

C<

D*.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*.txt' which matches wrong file types.

Using '<' which checks for smaller files, not larger.

Forgetting to quote "$file" in stat command.

Use '*.log' to match log files and '>' to check if file size is greater than 1MB (1048576 bytes).

5fill in blank

hard

Fill all three blanks to create a dictionary-like output of filenames and their sizes for '.csv' files in 'data' directory larger than 500 bytes.

Bash Scripting

declare -A sizes; for file in data/[1]; do size=$(stat -c%s "$file"); if [[ $size [2] 500 ]]; then sizes[[3]]=$size; fi; done; for f in "${!sizes[@]}"; do echo "$f: ${sizes[$f]} bytes"; done

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

A*.csv

B>

C"$file"

D*.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*.txt' which selects wrong files.

Using '<' which checks for smaller files.

Not quoting the filename as array key causing errors with spaces.

Use '*.csv' to select CSV files, '>' to check size greater than 500 bytes, and '"$file"' as the key in the associative array.

Practice

1. What does the following bash loop do?
for file in *; do echo "$file"; done

easy

A. It runs the echo command once without any output.

B. It deletes all files in the current folder.

C. It lists only directories in the current folder.

D. It prints the names of all files and directories in the current folder.

Solution

1. Step 1: Understand the loop variable and pattern

   The loop uses * which matches all files and directories in the current folder.

2. Step 2: Analyze the command inside the loop

   Each matched item is stored in file and printed with echo.

3. Final Answer:

   It prints the names of all files and directories in the current folder. -> Option D

4. Quick Check:

   Loop over * prints all names [OK]

Hint: Remember * matches all files and folders [OK]

Common Mistakes:

• Thinking * matches only files, not directories
• Assuming the loop deletes files
• Believing echo runs only once

2. Which of the following is the correct syntax to loop over all directories only in the current folder?

easy

A. for dir in *; do if [ -f "$dir" ]; then echo "$dir"; fi; done

B. for dir in *; do echo "$dir"; done

C. for dir in */; do echo "$dir"; done

D. for dir in /*; do echo "$dir"; done

Solution

1. Step 1: Understand the pattern for directories

   The pattern */ matches only directories in the current folder because directories end with a slash.

2. Step 2: Check the loop and echo command

   The loop iterates over directories and prints their names correctly.

3. Final Answer:

   for dir in */; do echo "$dir"; done -> Option C

4. Quick Check:

   */ matches directories only [OK]

Hint: Use */ pattern to match directories only [OK]

Common Mistakes:

• Using * matches files and directories, not only directories
• Using -f to check for directories instead of -d
• Using absolute path /* instead of current folder

3. What will be the output of this script if the current folder contains files: file1.txt, file2.txt and a directory docs/?

for item in *; do
  if [ -f "$item" ]; then
    echo "File: $item"
  else
    echo "Not a file: $item"
  fi
done

medium

A. File: file1.txt
File: file2.txt
Not a file: docs

B. File: file1.txt
File: file2.txt
File: docs

C. Not a file: file1.txt
Not a file: file2.txt
Not a file: docs

D. File: file1.txt
Not a file: file2.txt
Not a file: docs

Solution

1. Step 1: Identify file and directory checks

   The script uses [ -f "$item" ] to check if the item is a file.

2. Step 2: Apply checks to each item

   file1.txt and file2.txt are files, so print "File: ..."; docs is a directory, so print "Not a file: docs".

3. Final Answer:

   File: file1.txt File: file2.txt Not a file: docs -> Option A

4. Quick Check:

   -f true for files only [OK]

Hint: Use -f to test files, else it's not a file [OK]

Common Mistakes:

• Assuming directories pass -f test
• Confusing -f with -d
• Expecting directory names with trailing slash

4. Find the error in this script that tries to print only directories:

for item in *; do
  if [ -f "$item" ]; then
    echo "$item"
  fi
done

medium

A. The echo command is missing quotes around $item.

B. It uses -f to check files instead of -d for directories.

C. The loop pattern * does not match any files.

D. The script will print directories correctly.

Solution

1. Step 1: Understand the test used

   The script uses [ -f "$item" ] which checks if the item is a file, not a directory.

2. Step 2: Identify correct test for directories

   To check directories, [ -d "$item" ] should be used instead.

3. Final Answer:

   It uses -f to check files instead of -d for directories. -> Option B

4. Quick Check:

   Use -d to test directories [OK]

Hint: Use -d to check directories, not -f [OK]

Common Mistakes:

• Confusing -f and -d tests
• Assuming * matches only directories
• Ignoring quotes around variables

5. You want to count how many files (not directories) are in the current folder using a bash loop. Which script correctly does this?

hard

A. count=0
for item in *; do
if [ -f "$item" ]; then
count=$((count + 1))
fi
done
echo $count

B. count=0
for item in */; do
count=$((count + 1))
done
echo $count

C. count=0
for item in *; do
if [ -d "$item" ]; then
count=$((count + 1))
fi
done
echo $count

D. count=0
for item in *; do
count=$((count + 1))
done
echo $count

Solution

1. Step 1: Understand the goal

   We want to count files only, so we must check each item with [ -f "$item" ].

2. Step 2: Check each option

   count=0 for item in *; do if [ -f "$item" ]; then count=$((count + 1)) fi done echo $count correctly loops over all items, increments count only if item is a file, then prints count.

3. Final Answer:

   count=0 for item in *; do if [ -f "$item" ]; then count=$((count + 1)) fi done echo $count -> Option A

4. Quick Check:

   Use -f test and increment count [OK]

Hint: Increment count only if -f test passes [OK]

Common Mistakes:

• Counting directories instead of files
• Counting all items without checks
• Using */ pattern which matches directories only