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Quiz: Advanced Text Processing - Sed, Awk, and Pipes

Test your understanding of stream editing, data processing, and command pipelines.

1. What is the pipe operator | used for?

  1. Creating symbolic links
  2. Connecting the output of one command to the input of another
  3. Writing to multiple files simultaneously
  4. Running commands in parallel
Show Answer

The correct answer is B. The pipe | sends the standard output (stdout) of one command to the standard input (stdin) of another. For example, ls | grep ".txt" lists files and filters for those containing ".txt".

Concept Tested: Pipe Operator

See: Chapter 9 - Pipes

2. What does sed 's/old/new/g' file.txt do?

  1. Deletes all lines containing "old"
  2. Replaces all occurrences of "old" with "new"
  3. Searches for "old" and prints line numbers
  4. Sorts the file alphabetically
Show Answer

The correct answer is B. The sed substitution command s/old/new/g replaces all occurrences of "old" with "new". The g flag means "global" (all occurrences per line), without it only the first occurrence on each line is replaced.

Concept Tested: Sed Command, Text Substitution

See: Chapter 9 - Sed Substitution

3. What does > do in a command like ls > files.txt?

  1. Appends output to the file
  2. Redirects output to the file, overwriting it
  3. Reads input from the file
  4. Compares the output to the file
Show Answer

The correct answer is B. The > operator redirects standard output to a file, overwriting any existing content. Use >> to append instead of overwriting. For example, ls > files.txt saves the directory listing to files.txt.

Concept Tested: Output Redirection

See: Chapter 9 - Redirection

4. What does awk '{print $1}' file.txt do?

  1. Prints the first line of the file
  2. Prints the first field (column) of each line
  3. Prints only one copy of duplicate lines
  4. Deletes the first column
Show Answer

The correct answer is B. In awk, $1 refers to the first field (column) of each line, separated by whitespace by default. So awk '{print $1}' extracts and prints just the first word/column from each line.

Concept Tested: Awk Command

See: Chapter 9 - Awk Basics

5. What does 2> redirect?

  1. Standard output (stdout)
  2. Standard error (stderr)
  3. Standard input (stdin)
  4. The second line of output
Show Answer

The correct answer is B. File descriptor 2 is standard error. 2> redirects error messages to a file. For example, command 2> errors.txt saves error messages to errors.txt while normal output still goes to the terminal.

Concept Tested: Standard Error, Redirection

See: Chapter 9 - Error Redirection

6. What does the sort command do by default?

  1. Sorts numerically
  2. Sorts in reverse order
  3. Sorts lines alphabetically
  4. Removes duplicates
Show Answer

The correct answer is C. By default, sort sorts lines in alphabetical (lexicographic) order. Use -n for numerical sorting, -r for reverse order, and -u to also remove duplicates.

Concept Tested: Sort Command

See: Chapter 9 - Sort Command

7. What does uniq do and what's its requirement?

  1. Makes files unique by adding timestamps
  2. Removes duplicate adjacent lines (input must be sorted)
  3. Finds unique files in a directory
  4. Creates unique filenames
Show Answer

The correct answer is B. uniq removes duplicate adjacent lines. Since it only compares neighboring lines, you typically need to sort input first: sort file.txt | uniq. Use -c to count occurrences.

Concept Tested: Uniq Command

See: Chapter 9 - Uniq Command

8. What does cat file.txt | tr 'a-z' 'A-Z' do?

  1. Deletes lowercase letters
  2. Translates lowercase letters to uppercase
  3. Counts lowercase letters
  4. Transposes rows and columns
Show Answer

The correct answer is B. The tr (translate) command replaces characters. Here it maps each lowercase letter (a-z) to its uppercase equivalent (A-Z), effectively converting the entire file to uppercase.

Concept Tested: Tr Command

See: Chapter 9 - Tr Command

9. What does &> do in bash?

  1. Runs command in background
  2. Redirects both stdout and stderr to a file
  3. Creates an alias
  4. Appends to a file
Show Answer

The correct answer is B. The &> operator redirects both standard output (stdout) and standard error (stderr) to the same file. It's equivalent to > file 2>&1. For example, command &> output.txt captures all output.

Concept Tested: Redirection

See: Chapter 9 - Combined Redirection

10. What does cut -d',' -f2 data.csv do?

  1. Cuts the file into two pieces
  2. Extracts the second comma-separated field from each line
  3. Removes the second line
  4. Deletes commas from the file
Show Answer

The correct answer is B. The cut command extracts portions of text. Here -d',' sets the delimiter to comma, and -f2 selects the second field. This is perfect for extracting columns from CSV files.

Concept Tested: Cut Command

See: Chapter 9 - Cut Command