Class 22

Question 1

What are control structures?

Answer 1

syntactic structures that control how and when other statements are executed

Question 2

What are the two basic types of control structures?

Answer 2

conditionals and loops

Question 3

What is the basic format of the if … then construct?

Answer 3

if COMMAND
then
COMMAND_1
COMMAND_2
…
fi

Question 4

How is the command that follows if used to determine whether or not the statements between the then and fi keywords are executed?

Answer 4

if the command returns an exit status of 0 the statements are executed

Question 5

What does an exit status of 0 mean?

Answer 5

that the command that returned the status code ran without error

Question 6

What are the two keywords that surround the statements inside an if statement?

Answer 6

then and fi

Question 7

Can the then keyword appear on the same line as if ?

Answer 7

yes, but only if it is separated from it by a semicolon (;)

Question 8

What does the test command do?

Answer 8

analyze a logical expression and return an exit status that tells whether the expression is true or false

Question 9

What is the value of the exit status returned by test to indicate that the expression is true?

Answer 9

0

Question 10

Does the command that follows if need to be test?

Answer 10

no, it can be any command that returns an exit status