Which of the following shell scripts (if any) correctly prints TRUE if x and y are both equal to 10? Select all that apply.

Question

BlackTom AI · Accepted Answer

We are evaluating which shell scripts correctly print TRUE when x and y are both equal to 10, considering how test ([ ]) works in POSIX shells and common bash syntax.
Option 1: if [ $x == 10 & $y == 10 ]; then echo TRUE fi
This uses == for string comparison and & as a background operator, not a logical AND inside [ ]. In many shells, [ ... ] with == is treated as a string comparison, which is acceptable, but the single & outside the test is a background operator that would separate commands, not combine the two tests. Moreover, there is no closing fi on its own line, but that is a formatting issue. Overall, this does not correctly perform a joint numeric comparison with both variables equal to 10, so it is incorrect.
Option 2: None of the other answers is correct
This claims that no script would print TRUE for x=10 and y=10. Since we will see that at least one option does print TRUE under standard interpretations, this statement is not accurate. Therefore, this option is incorrect.
Option 3: if [ $x -eq 10 -a $y -eq 10 ]; then
This uses numeric comparison (-eq) for both x and y and the -a operator to combine the tests inside [ ]. This is the canonical way to check that both conditions hold simultaneously: x equals 10 and y equals 10. If x and y are 10, both subtests are true, and the overall test is true, so TRUE would be echoed. Thus this option is correct for the intended condition.
Option 4: if [ $x == 10 && $y == 10 ]; then echo TRUE fi
Inside [ ], the operators must be part of a single test expression. Using && inside [ ] is not POSIX-compliant for test within [ ]; some shells may support it as a shell operator outside of the test, but not inside. Additionally, using == for numeric comparison is acceptable for string equality, but since the overall structure is not a proper numeric test and && is not processed as a logical AND inside that form, this will not reliably evaluate to true when x and y are 10. Therefore, this option is incorrect.
Option 5: if [ $x = 10 && $y = 10 ]; then echo TRUE fi
Similar to option 4, [ ] does not interpret && as a logical AND inside the test, and = is the string equality operator, not a numeric comparison. Even if the shell expands variables, the overall expression would not evaluate as intended for the conjunction of both equals-to-10 checks. This makes the option incorrect.
In summary, the only script that reliably prints TRUE when x and y are both 10 uses numeric tests combined with a proper logical conjunction inside the test command (option 3). The other options misuse operators or rely on syntax that is not portable or valid within a single [ ... ] test expression.

Which of the following shell scripts (if any) correctly prints TRUE if x and y are both equal to 10? Select all that apply.多项选择题

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