05 Commands

Question 1

In Linux, “commands” refers to any of four different subtypes. What are those subtypes?

Answer 1

1. An executable program (like those in /usr/bin)
2. A shell “built-in”
3. A shell function
4. A command alias

Question 2

What is an executable program?

Answer 2

A compiled binary written in a programming or scripting language. Typically located in /usr/bin

Question 3

What is a shell built-in?

Answer 3

Shell built-ins are written into the shell itself.

Question 4

What is an example of a shell built-in?

Answer 4

cd

Question 5

What is a shell function?

Answer 5

A miniature shell script, incorporated into the shell environment

Question 6

What is an alias?

Answer 6

A user-defined command, often built using other commands.

Question 7

What is the purpose of the “type” command?

Answer 7

The “type” command is a shell built-in that displays a commands subtype.

Question 8

What is the purpose of the “which” command?

Answer 8

“which” displays an executables path location. note that “which” only works for executables, not built-ins, aliases, etc.

Question 9

What is an “alias”

Answer 9

an alias is a command built from other system commands, separated by semicolons

Question 10

What is the method for creating an alias?

Answer 10

Aliases take the form “alias name=’string’ “

Question 11

What should you do immediately prior to creating an alias?

Answer 11

Check to see if the intended alias is already resident on the system. One way to do that is “ type alias “

Question 12

How would you list all available aliases created on a system?

Answer 12

Simply entering the “alias” command followed by ENTER

Question 13

How would you remove an alias if you no longer wished to use it?

Answer 13

unalias foo