sort and uniq in pipelines in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the lines of a file named 'data.txt'.

Bash Scripting

sort [1]

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

A-r

Bdata.txt

C-u

Ddata.csv

Attempts:

3 left

💡 Hint

Common Mistakes

Using options like -r or -u instead of the filename.

Typing the wrong filename.

The 'sort' command followed by the filename 'data.txt' sorts the lines in that file.

2fill in blank

medium

Complete the pipeline to sort the output of 'cat data.txt' and remove duplicate lines.

Bash Scripting

cat data.txt | sort | [1]

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

Agrep

Bhead

Cwc

Duniq

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'grep' or 'wc' instead of 'uniq'.

Not sorting before using 'uniq'.

The 'uniq' command removes duplicate lines from sorted input.

3fill in blank

hard

Fix the error in the pipeline that tries to remove duplicates but does not sort first.

Bash Scripting

cat data.txt | [1] | uniq

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

Asort

Bgrep

Chead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'grep' or 'head' instead of 'sort'.

Not sorting before 'uniq'.

The 'uniq' command only removes adjacent duplicates, so sorting first is necessary.

4fill in blank

hard

Fill both blanks to create a pipeline that sorts 'data.txt' in reverse order and removes duplicates.

Bash Scripting

cat data.txt | sort [1] | uniq [2]

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

A-r

B-c

C-d

D-u

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-c' or '-d' with 'uniq' instead of '-u'.

Not using '-r' to reverse sort.

The '-r' option sorts in reverse order, and '-u' makes 'uniq' output unique lines only.

5fill in blank

hard

Fill all three blanks to create a pipeline that counts how many times each unique line appears in 'data.txt', sorted by count descending.

Bash Scripting

cat data.txt | sort | uniq [1] | sort [2] -k1,1n | sort [3] -k1,1nr

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

A-c

B-k

C-r

D-u

Attempts:

3 left

💡 Hint

Common Mistakes

Not using '-c' with 'uniq' to count.

Wrong sort options or missing reverse sort.

The '-c' option counts duplicates, '-k' specifies sort key, and '-r' sorts in reverse order for descending counts.

Practice

1. What is the main purpose of using sort | uniq together in a bash pipeline?

easy

A. To get a sorted list with duplicates removed

B. To count the number of lines in a file

C. To sort lines but keep duplicates

D. To find the longest line in a file

Solution

1. Step 1: Understand what sort does

   The sort command arranges lines in alphabetical or numerical order.

2. Step 2: Understand what uniq does after sorting

   The uniq command removes duplicate adjacent lines, so sorting first groups duplicates together for removal.

3. Final Answer:

   To get a sorted list with duplicates removed -> Option A

4. Quick Check:

   sort + uniq = sorted unique lines [OK]

Hint: Always sort before uniq to remove all duplicates [OK]

Common Mistakes:

• Using uniq before sort, which misses duplicates
• Thinking uniq counts lines instead of removing duplicates
• Assuming sort removes duplicates by itself

2. Which of the following is the correct syntax to remove duplicate lines from file.txt and sort the output?

easy

A. uniq file.txt | sort

B. sort file.txt | uniq

C. sort | uniq file.txt

D. uniq | sort file.txt

Solution

1. Step 1: Identify correct command order

   The file must be sorted first, so sort file.txt comes before uniq.

2. Step 2: Check syntax correctness

   sort file.txt | uniq correctly pipes sorted output to uniq for duplicate removal.

3. Final Answer:

   sort file.txt | uniq -> Option B

4. Quick Check:

   sort first, then uniq = correct syntax [OK]

Hint: Pipe sorted output into uniq: sort file | uniq [OK]

Common Mistakes:

• Placing uniq before sort, which fails to remove all duplicates
• Incorrect pipe placement causing syntax errors
• Trying to pass file as argument to uniq instead of sort

3. Given a file names.txt with contents:

bob
alice
bob
carol
alice
bob

What is the output of sort names.txt | uniq?

medium

A. alice
bob
bob
carol
alice
bob

B. bob
alice
carol

C. bob
carol
alice

D. alice
bob
carol

Solution

1. Step 1: Sort the file contents

   Sorting lines alphabetically gives: alice, alice, bob, bob, bob, carol.

2. Step 2: Apply uniq to remove duplicates

   Uniq removes repeated adjacent lines, resulting in: alice, bob, carol.

3. Final Answer:

   alice\nbob\ncarol -> Option D

4. Quick Check:

   sort + uniq = unique sorted lines [OK]

Hint: Sort first to group duplicates, then uniq removes repeats [OK]

Common Mistakes:

• Not sorting first, so uniq misses duplicates
• Expecting original order instead of sorted
• Confusing uniq output with counting duplicates

4. You run uniq file.txt | sort to remove duplicates and sort lines, but duplicates remain. What is the likely problem?

medium

A. uniq only removes adjacent duplicates, so sorting after uniq misses duplicates

B. sort command is not working without options

C. file.txt is empty, so no output

D. uniq requires -c option to remove duplicates

Solution

1. Step 1: Understand uniq behavior

   Uniq removes only adjacent duplicate lines, so if duplicates are scattered, it won't remove them.

2. Step 2: Analyze command order effect

   Sorting after uniq means duplicates are not grouped before uniq runs, so duplicates remain.

3. Final Answer:

   uniq only removes adjacent duplicates, so sorting after uniq misses duplicates -> Option A

4. Quick Check:

   uniq needs sorted input to remove all duplicates [OK]

Hint: Sort before uniq to group duplicates for removal [OK]

Common Mistakes:

• Thinking uniq removes all duplicates regardless of order
• Believing sort alone removes duplicates
• Using uniq -c instead of uniq for removal

5. You have a log file access.log with many repeated IP addresses scattered randomly. You want a sorted list of unique IPs. Which command pipeline correctly achieves this?

hard

A. cat access.log | uniq | sort

B. uniq access.log | sort

C. sort -u access.log

D. uniq access.log | sort -u

Solution

1. Step 1: Understand sort -u option

   sort -u sorts and removes duplicates in one step efficiently.

2. Step 2: Why others fail

   Options A, B, and D all apply uniq before sorting, missing non-adjacent duplicates since IPs are scattered randomly.

3. Final Answer:

   sort -u access.log -> Option C

4. Quick Check:

   sort -u = sorted unique lines in one command [OK]

Hint: Use sort -u for sorted unique lines in one step [OK]

Common Mistakes:

• Using uniq before sort, missing duplicates
• Not knowing sort -u combines sorting and uniqueness
• Using unnecessary cat command