What output is produced by the following command sequence? echo `1 2 3 4 5 6' | while read a b c; do echo result $c $b $a; done

The correct answer is C. result: 3 4 5 6 2 1. Option C is correct because read a b c splits the input 1 2 3 4 5 6 by whitespace and assigns words left-to-right - but the last variable absorbs all remaining tokens: a=1, b=2, c="3 4 5 6". The echo result $c $b $a then prints those three variables in reversed order, yielding…

Shells and Shell Scripting

Question

What output is produced by the following command sequence? echo `1 2 3 4 5 6' | while read a b c; do echo result $c $b $a; done

Options

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

How the community answered

(32 responses)

A
3% (1)
B
9% (3)
C
78% (25)
D
3% (1)
E
6% (2)

Explanation

Option C is correct because read a b c splits the input 1 2 3 4 5 6 by whitespace and assigns words left-to-right - but the last variable absorbs all remaining tokens: a=1, b=2, c="3 4 5 6". The echo result $c $b $a then prints those three variables in reversed order, yielding result 3 4 5 6 2 1.

Why the distractors fail:

E (result 3 2 1) is the trap - it assumes c=3 only, forgetting the last-variable-catches-all rule.
D (result 6 5 4 3 2 1) would require the entire string to be fully reversed, which read doesn't do.
A (result 6 5 4) would require only the last three tokens assigned to c b a - the opposite assignment logic.
B (result 1 2 3 4 5 6) would result if the variables were echoed in original order with no splitting.

Memory tip: When read has fewer variables than words, think of the last variable as a bucket - it catches everything the earlier variables didn't claim. Apply this before reversing the echo order.

Topics

#read command#pipes and redirection#variable expansion#word splitting

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