Shell command (1 mark)How many lines will be output by the following shell command? cat data.csv | awk -F’,’ ’rand()

Question

Shell command (1 mark)How many lines will be output by the following shell command? cat data.csv | awk -F’,’ ’rand()<9/10 {print $9}’[Fill in the blank]

BlackTom AI · Accepted Answer

The question asks how many lines will be output by the pipeline: cat data.csv | awk -F’,’ ’rand()<9/10 {print $9}’.

First, consider what the awk command is doing: -F’,’ sets the input field separator to a comma, so $9 refers to the 9th field in each line. The condition rand()<9/10 is a per-line test that uses the built-in rand() function, which generates a random number uniformly distributed between 0 and 1. The condition is true for roughly 9/10 of the possible values, i.e., about 90% of the lines will satisfy it. When the condition is true, awk executes {print $9}, so it prints the 9th field for that line.

Option A: 'approximately 9% of the lines in the original file' — This is incorrect because the probability is 0.9, not 0.1, so roughly 90% are expected to pass the test, not 9%.

Option B: 'approximately 90% of the lines in the original file' — This matches the probabilistic behavior of rand()<9/10, so most lines (about nine-tenths) will print their 9th field.

Option C: 'impossible to tell' — In practice, with a random-number test, we can’t predict the exact count for a specific file, but we can characterize the approximate proportion as 90%. The question asks for the expected proportion, which is well-defined, so this statement is not accurate.

Option D: 'exactly 10' — This asserts a fixed, exact count of 10 lines, which would be true only for a tiny, specific dataset and is not how a probabilistic test behaves across a file of unknown length. It is incorrect to claim an exact number here.

In summary, the correct interpretation is that the command prints the 9th field for about 90% of the lines, so the best choice is option B. The other options misstate the probability, claim impossibility where a probabilistic expectation exists, or fix an exact count that does not align with the random test.

Shell command (1 mark)How many lines will be output by the following shell command? cat data.csv | awk -F’,’ ’rand()<9/10 {print $9}’[Fill in the blank]单项选择题

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