Class 21

Question 1

What does Bash do when it performs history expansion?

Answer 1

it reruns an old command line which it retrieves from the history list

Question 2

What does Bash do when it performs alias substitution?

Answer 2

it replaces the name of the alias with a Unix command

Question 3

Write the command you would use to create the files foo1.txt to foo5.txt using brace expansion and the touch command.

Answer 3

touch foo{1,2,3,4,5}.txt

Question 4

What does Bash do when it performs tilde (~) expansion?

Answer 4

replaces ~ with the absolute address of your home directory or replaces ~UNIX_USERNAME with the absolute address of the home directory of UNIX_USERNAME

Question 5

What does Bash do when it performs parameter and variable expansion?

Answer 5

substitutes the value of a variable or a parameter for the name of the variable or parameter when preceded by a $

Question 6

What does Bash do when it performs arithmetic expansion?

Answer 6

treats the digits inside double parentheses as numbers, performs arithmetic operations on them and substitutes the result of that calculation for the expansion expression

Question 7

What does Bash do when it performs command substitution?

Answer 7

runs the commands inside the parentheses in a subshell and substitutes the output from those commands for the substitution expression

Question 8

What would you write at the command line to define the alias ll whose value was ls -l ?

Answer 8

alias ll=’ls -l’

Question 9

Can an alias be made global?

Answer 9

no

Question 10

Can a function be made global?

Answer 10

no