cut and paste in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of cut command with delimiter and field

What is the output of this command when run on the file data.txt containing:

apple,banana,cherry
dog,elephant,fox

Command:

cut -d',' -f2 data.txt

Bash Scripting

cut -d',' -f2 data.txt

A

cherry
fox

B

apple
dog

C

banana
elephant

D

apple,banana,cherry
dog,elephant,fox

💡 Hint

The -d option sets the delimiter, and -f selects the field number.

The command cuts the second field separated by commas, so it outputs 'banana' and 'elephant' each on a new line.

💻 Command Output

intermediate

Paste command combining two files

Given two files:

file1.txt:
1
2
3

file2.txt:
a
b
c

What is the output of:

paste file1.txt file2.txt

Bash Scripting

paste file1.txt file2.txt

A

1
2
3
a
b
c

B

1  a
2  b
3  c

C

1a
2b
3c

D

1	a
2	b
3	c

💡 Hint

Paste joins lines from files side by side separated by tabs by default.

Paste combines lines from both files separated by a tab character, so each line from file1.txt is joined with the corresponding line from file2.txt.

📝 Syntax

advanced

Correct cut command to extract characters

Which option correctly extracts characters 3 to 5 from each line of input.txt?

A cut -f3-5 input.txt

B cut -c3-5 input.txt

C cut -d3-5 input.txt

D cut -c3,5 input.txt

💡 Hint

Use -c to select character positions.

Option B uses -c3-5 to select characters from position 3 to 5. Option B uses fields which is incorrect here. Option B uses an invalid delimiter. Option B selects characters 3 and 5 only, not the range.

💻 Command Output

advanced

Output of paste with custom delimiter

Given two files:

names.txt:
John
Jane

ages.txt:
30
25

What is the output of:

paste -d ':' names.txt ages.txt

Bash Scripting

paste -d ':' names.txt ages.txt

A

John:30
Jane:25

B

John 30
Jane 25

C

John:Jane
30:25

D

John
Jane
30
25

💡 Hint

The -d option sets the delimiter between pasted columns.

Paste joins lines from both files with ':' as delimiter, so each name is joined with the corresponding age separated by a colon.

🚀 Application

expert

Combine cut and paste to swap columns

You have a file data.csv with comma-separated values:

red,apple
blue,berry
green,grape

Which command sequence swaps the two columns so output is:

apple,red
berry,blue
grape,green

A paste -d',' <(cut -d',' -f2 data.csv) <(cut -d',' -f1 data.csv)

B cut -d',' -f2 data.csv | paste -d',' - <(cut -d',' -f1 data.csv)

C cut -d',' -f2 data.csv > temp1; cut -d',' -f1 data.csv > temp2; paste -d',' temp1 temp2

D cut -d',' -f1 data.csv | paste -d',' - <(cut -d',' -f2 data.csv)

💡 Hint

Use process substitution to cut columns and paste them in swapped order.

Option A correctly cuts the second column first, then the first column, and pastes them with comma delimiter, swapping columns. Option A pipes first cut but incorrectly uses paste with pipe and process substitution causing mismatch. Option A uses temp files but is correct in output; however, it is less elegant and not a single command sequence. Option A pastes original order, not swapped.

Practice

1. What does the cut command do in bash scripting?

easy

A. Deletes lines containing a specific pattern

B. Extracts specific parts of each line from a file or input

C. Joins lines from multiple files side by side

D. Counts the number of lines in a file

Solution

1. Step 1: Understand the purpose of cut

   The cut command is used to extract sections from each line of input, usually by specifying fields or characters.

2. Step 2: Compare with other commands

   paste joins lines side by side, grep deletes or filters lines, and wc counts lines. So, only cut extracts parts of lines.

3. Final Answer:

   Extracts specific parts of each line from a file or input -> Option B

4. Quick Check:

   cut = Extract parts [OK]

Hint: Remember: cut slices parts, paste sticks lines side by side [OK]

Common Mistakes:

• Confusing cut with paste
• Thinking cut deletes lines
• Assuming cut counts lines

2. Which of the following is the correct syntax to extract the 2nd field from a colon-separated file using cut?

easy

A. cut -f 2 -d ':' filename

B. cut -d 2 -f ':' filename

C. cut -c 2 filename

D. cut -f ':' -d 2 filename

Solution

1. Step 1: Identify correct option flags for cut

   The -f flag specifies the field number, and -d specifies the delimiter character.

2. Step 2: Match syntax to extract 2nd field with ':' delimiter

   cut -f 2 -d ':' filename uses -f 2 and -d ':', which is the correct order and syntax.

3. Final Answer:

   cut -f 2 -d ':' filename -> Option A

4. Quick Check:

   Fields (-f) then delimiter (-d) [OK]

Hint: Use -f for field, -d for delimiter in cut [OK]

Common Mistakes:

• Swapping -f and -d flags
• Using -c instead of -f for fields
• Putting delimiter as field number

3. Given two files, file1.txt contains:
apple banana cherry
and file2.txt contains:
red yellow red
What is the output of paste file1.txt file2.txt?

medium

A. appleyellow
bananared
cherryred

B. apple
banana
cherry
red
yellow
red

C. apple red
banana yellow
cherry red

D. apple,red
banana,yellow
cherry,red

Solution

1. Step 1: Understand paste command behavior

   paste joins lines from two files side by side separated by a tab by default.

2. Step 2: Combine lines from both files line by line

   Line 1: apple + tab + red
   Line 2: banana + tab + yellow
   Line 3: cherry + tab + red

3. Final Answer:

   apple red banana yellow cherry red -> Option C

4. Quick Check:

   paste joins lines side by side [OK]

Hint: paste joins lines horizontally, not vertically [OK]

Common Mistakes:

• Thinking paste stacks lines vertically
• Assuming paste adds commas
• Ignoring tab separator default

4. What is wrong with this command to extract the first 3 characters of each line?
cut -c 1-3 file.txt
It returns an error. Why?

medium

A. The command is correct; error likely from missing file

B. The range should be specified as 1,3 not 1-3

C. The -c option does not accept ranges

D. The syntax is correct; error is from file permissions

Solution

1. Step 1: Check cut syntax for character ranges

   cut -c 1-3 is the correct syntax to extract characters 1 to 3.

2. Step 2: Consider other reasons for error

   If an error occurs, it is likely due to the file not existing or permission issues, not syntax.

3. Final Answer:

   The command is correct; error likely from missing file -> Option A

4. Quick Check:

   cut -c 1-3 is valid syntax [OK]

Hint: Check file existence before blaming cut syntax [OK]

Common Mistakes:

• Thinking cut -c doesn't accept ranges
• Using commas instead of dash for ranges
• Ignoring file existence or permissions

5. You have two files:
names.txt with:
John Jane Doe
and ages.txt with:
25 30
You want to create a file combined.txt where each line has name and age separated by a comma. Missing ages should show as 'N/A'. Which command sequence achieves this?

hard

A. paste -d ',' names.txt ages.txt > combined.txt

B. paste names.txt ages.txt | sed 's/$/,N\/A/' > combined.txt

C. cut -d ',' -f 1 names.txt > combined.txt

D. paste -d ',' names.txt ages.txt | sed 's/,$/,N\/A/' > combined.txt

Solution

1. Step 1: Use paste with comma delimiter

   paste -d ',' names.txt ages.txt joins lines with a comma.

2. Step 2: Handle missing ages with sed

   Lines missing age end with a comma only, so sed 's/,$/,N\/A/' replaces trailing comma with ',N/A'.

3. Step 3: Redirect output to combined.txt

   Using > combined.txt saves the result to the file.

4. Final Answer:

   paste -d ',' names.txt ages.txt | sed 's/,$/,N\/A/' > combined.txt -> Option D

5. Quick Check:

   paste + sed fixes missing fields [OK]

Hint: Use paste with -d and sed to fix missing fields [OK]

Common Mistakes:

• Not handling missing age lines
• Using cut instead of paste for joining
• Forgetting to redirect output to file