LFCS Question #547: Real Exam Question with Answer & Explanation

Question

Which of the following outputs will the below command sequence produce? echo '1 2 3 4 5 6' | while read a b c; do echo result: $c $b $a; done

Options

• Aresult: 3 4 5 6 2 1
• Bresult: 1 2 3 4 5 6
• Cresult: 6 5 4
• Dresult: 6 5 4 3 2 1
• Eresult: 3 2 1

Explanation

The echo command pipes a single line of space-separated numbers to a while read loop, which assigns the first two words to a and b, and all remaining words to c, then echoes them in reverse order.

Common mistakes.

• B. This output implies the variables were not assigned correctly or were echoed in their original order.
• C. This output only shows the last three numbers, indicating an incorrect understanding of how read handles multiple words with multiple variables.
• D. This output implies a complete reversal of all numbers, which would only happen if each number was read into a separate variable and then processed.
• E. This output implies only the first three numbers were processed and reversed, but read assigns all remaining words to the last variable.

Concept tested. Bash read command behavior

Reference. https://www.gnu.org/software/bash/manual/bash.html#index-read

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