File globbing (wildcards *, ?, []) in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to list all files ending with '.txt' in the current directory.

Linux CLI

ls [1]

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

A*.txt

B?txt

C[a-z].txt

Dtxt*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '?txt' matches only files with exactly one character before 'txt'.

Using 'txt*' matches files starting with 'txt', not ending.

Using '[a-z].txt' matches only files with a single lowercase letter before '.txt'.

The wildcard '*.txt' matches all files ending with '.txt'.

2fill in blank

medium

Complete the code to list files with exactly three characters and ending with '.log'.

Linux CLI

ls [1]

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

A*.???

B?*.log

C???.log

D*.log

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*.log' matches any number of characters, not exactly three.

Using '*.???' matches files with any name and three-character extension.

Using '?*.log' matches files with at least one character before '.log', not exactly three.

The pattern '???.log' matches files with exactly three characters before '.log'.

3fill in blank

hard

Fix the error in the code to list files starting with 'data' followed by any single character and ending with '.csv'.

Linux CLI

ls data[1].csv

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

A*

B?

C[]

D[?]

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' matches zero or more characters, not exactly one.

Using '[]' or '[?]' is incorrect syntax for matching a single character.

The '?' wildcard matches exactly one character, so 'data?.csv' matches files like 'data1.csv'.

4fill in blank

hard

Fill both blanks to list files that start with 'log', followed by a digit between 1 and 3, and ending with '.txt'.

Linux CLI

ls log[1][2].txt

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

A[1-3]

B?

C*

D[a-z]

Attempts:

3 left

💡 Hint

Common Mistakes

Using '?' after '[1-3]' matches exactly one character, but we want any number.

Using '[a-z]' matches letters, not digits.

Using '*' alone does not restrict the digit.

The pattern '[1-3]*' matches files starting with 'log', then a digit 1 to 3, then any characters, ending with '.txt'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps filenames to their extensions for files with names starting with 'img' and extensions '.jpg' or '.png'.

Linux CLI

files = ['img1.jpg', 'img2.png', 'img3.gif']
result = { [1]: [2] for file in files if file.startswith('img') and file.endswith([3]) }

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

Afile

Bfile.split('.')[-1]

C('.jpg', '.png')

Dfile.split('.')

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'file.split('.')' returns a list, not the extension string.

Using a single string in endswith instead of a tuple misses multiple extensions.

Using wrong keys or values in the dictionary comprehension.

The comprehension maps each filename to its extension by splitting on '.' and filtering files ending with '.jpg' or '.png'.

Practice

1. Which wildcard pattern matches all files with any extension starting with log in their name?

easy

A. log* only matches files named exactly 'log'

B. log?

C. log[0-9]

D. log*

Solution

1. Step 1: Understand the wildcard *

   The * matches zero or more characters, so log* matches any file starting with 'log' followed by anything or nothing.

2. Step 2: Compare other options

   log? matches 'log' plus exactly one character, log[0-9] matches 'log' plus one digit, and the last option is incorrect about log*.

3. Final Answer:

   log* -> Option D

4. Quick Check:

   Wildcard * matches any characters [OK]

Hint: Use * to match any number of characters [OK]

Common Mistakes:

• Confusing * with ? wildcard
• Thinking * matches only one character
• Misunderstanding [] as matching multiple characters

2. Which of the following is the correct pattern to match files named data1, data2, but not data10?

easy

A. data?

B. data*

C. data[1-9]

D. data??

Solution

1. Step 1: Understand the pattern data[1-9]

   This matches 'data' followed by exactly one digit from 1 to 9, so it matches 'data1' and 'data2' but not 'data10'.

2. Step 2: Check other patterns

   data? matches 'data' plus any one character (including letters), data* matches 'data' plus any characters (including 'data10'), and data?? matches 'data' plus exactly two characters (so it matches 'data10').

3. Final Answer:

   data[1-9] -> Option C

4. Quick Check:

   Square brackets match one character from set [OK]

Hint: Use [ ] to match one character from a range [OK]

Common Mistakes:

• Using * which matches too many files
• Using ? which matches any single character, not range
• Confusing number of characters matched

3. Given files: file1.txt, file2.txt, fileA.txt, fileB.txt, what files does the pattern file?.txt match?

medium

A. file1.txt, file2.txt

B. file1.txt, file2.txt, fileA.txt, fileB.txt

C. fileA.txt, fileB.txt

D. file.txt

Solution

1. Step 1: Understand the pattern file?.txt

   The ? matches exactly one character, so it matches any file named 'file' plus one character plus '.txt'.

2. Step 2: Check which files match

   All files with names 'file1.txt', 'file2.txt', 'fileA.txt', and 'fileB.txt' have exactly one character after 'file' before '.txt', so all match.

3. Final Answer:

   file1.txt, file2.txt, fileA.txt, fileB.txt -> Option B

4. Quick Check:

   ? matches exactly one character [OK]

Hint: Use ? to match exactly one character [OK]

Common Mistakes:

• Thinking ? matches zero or multiple characters
• Confusing ? with *
• Ignoring file extension in pattern

4. You want to list files named report1, report2, and report3 only. Which pattern is incorrect?

medium

A. report*

B. report?

C. report[1-3]

D. report[123]

Solution

1. Step 1: Analyze pattern report*

   This matches 'report' plus any characters, so it matches more than just 'report1', 'report2', and 'report3'. It includes 'report10', 'report_final', etc.

2. Step 2: Check other patterns

   report[1-3] and report[123] match exactly one character from 1,2,3 after 'report'. report? matches 'report' plus any one character, which includes 'report1', 'report2', 'report3' but also others with one character.

3. Final Answer:

   report* -> Option A

4. Quick Check:

   * matches too many files [OK]

Hint: Use [] to limit characters, * matches too many [OK]

Common Mistakes:

• Using * when exact matches needed
• Assuming ? limits to digits only
• Not realizing [] matches one character only

5. You have files: img01.png, img02.png, img10.png, img20.png. Which pattern matches only files with numbers from 01 to 09?

hard

A. img0[1-9].png

B. img[0-9][1-9].png

C. img??.png

D. img[01-09].png

Solution

1. Step 1: Understand pattern img0[1-9].png

   This matches 'img0' plus one digit from 1 to 9, then '.png'. So it matches 'img01.png' to 'img09.png'.

2. Step 2: Check other patterns

   img[0-9][1-9].png matches any two digits, including 'img10.png' and 'img20.png'. img??.png matches any two characters after 'img', so all files. img[01-09].png is invalid syntax because ranges like '01-09' are not valid inside [].

3. Final Answer:

   img0[1-9].png -> Option A

4. Quick Check:

   Use 0 then [1-9] for numbers 01-09 [OK]

Hint: Use fixed digit then range in [] for number ranges [OK]

Common Mistakes:

• Using invalid range syntax inside []
• Using ?? which matches any two characters
• Not fixing leading zero for 01-09