1.3 Environment Variables

Question 2

How do you preserve the current value of the PATH environment variable when adding a new value to it?

Answer 2

To preserve the current value of the PATH environment variable when appending paths to it, put $PATH. For example, PATH=$PATH:/additional/path.

Question 3

What are the two different types of variables?

Answer 3

The two different types of varables are user-defined variables and environment variables.

Question 4

What is a user-defined variable?

Answer 4

Variables assigned with a name and contents of your choice. Does not change the shell environment or how the shell works.

Question 5

What is an environment variable?

Answer 5

An environment variable is a setting that the operating system or programs working in the operating system access. Environment variables make up the user environment.

Question 6

What is the standard for environment variable names?

Answer 6

The standard for writing variables names (called variable identifiers) is to use all upper-case letters (e.g., SHELL and EUID).

Question 7

What do environment variables become when you change them from the defaults?

Answer 7

Changing environmental variables from the defaults result in user-defined variables.

Question 8

What is a user-defined variable?

Answer 8

A user-defined variable is a variable that applies only to the current session.

Question 9

How do you make a user-defined environement variable apply to child sessions?

Answer 9

Exporting user-defined variables makes them apply to child sessions.

Question 10

How do you make user-defined environment variables persistent?

Answer 10

Add user-defined variables to the shell configuration files to make them persistent.

Question 11

What does the BASH environment variable contain?

Answer 11

The BASH environment variable contains the location of the bash executable file.

Question 12

What does the SHELL environment variable contain?

Answer 12

The SHELL environment variable contains the user’s login shell.

Question 13

What does the CPU environment variable contain?

Answer 13

The CPU environment variable contains the type of CPU.

Question 14

What does the DISPLAY environment variable contain?

Answer 14

The DISPLAY environment variable contains the location where X Windows output goes. Can be used to send X-windows output to another machine.

Question 15

What does the ENV environment variable contain?

Answer 15

The ENV environment variable contains the location of the configuration file for the current shell.

Question 16

What does the EUID environment variable contain?

Answer 16

The EUID environment variable contains the ID number of the current user.

Question 17

What does the HISTFILE environment variable contain?

Answer 17

The HISTFILE environment variable contains the filename where past commands are stored. For Bash, it’s usually ~/.bash_history.

Question 18

What does the HISTSIZE environment variable contain?

Answer 18

The HISTSIZE environment variable contains the number of past commands that HISTFILE stores for the current session.

Question 19

What does the HISTFILESIZE environment variable contain?

Answer 19

The HISTFILESIZE environment variable contains the number of past commands that HISTFILE stores for the multiple sessions.

Question 20

What does the HOME environment variable contain?

Answer 20

The HOME environment variable contains the absolute path of the user’s home directory.

Question 21

What does the HOST environment variable contain?

Answer 21

The HOST environment variable contains the name of the computer.

Question 22

What does the HOSTNAME environment variable contain?

Answer 22

The HOSTNAME environment variable contains the name of the computer. It is identical to HOST, but used on certain distributions.

Question 23

What does the INFODIR environment variable contain?

Answer 23

The INFODIR environment variable contains the path to the computer’s information pages.

Question 24

What does the LOGNAME environment variable contain?

Answer 24

The LOGNAME environment variable contains the user name of the current user.

Question 25

What does the MAIL environment variable contain?

Answer 25

The MAIL environment variable contains the path to the current user’s mailbox file. Usually /var/spool/mail/username.

Question 26

What does the **MANPATH** environment variable contain?

Answer 26

The **MANPATH** environment variable contains the path to the computer's man pages. Usually **/usr/local/man**.

Question 27

What does the **OLDPWD** environment variable contain?

Answer 27

The **OLDPWD** environment variable contains the path of the directory the user was in prior to the current path.

Question 28

What does the **OSTYPE** environment variable contain?

Answer 28

The **OSTYPE** environment variable contains the type of operating system. Usually this is Linux.

Question 29

What does the **PATH** environment variable contain?

Answer 29

The **PATH** environment variable contains the directory prefixes used to search for programs and files: * Use a colon (:) to separate entries in the **PATH** variable. * Do not include a period (.) in the **PATH** variable. A period indicates that the working directory is in the path, and this poses a security risk.

Question 30

What does the **PS1** environment variable contain?

Answer 30

The **PS1** environment variable contains the characters the shell uses to indicate normal user ($), root user (#) and similar items.

Question 31

What does the **PWD** environment variable contain?

Answer 31

The **PWD** environment variable contains the path of the current working directory.

Question 32

What does the **LANG** environment variable contain?

Answer 32

The **LANG** environment variable contains the language the operating system uses.

Question 33

What does the **PAGER** environment variable contain?

Answer 33

The **PAGER** environment variable contains used by the man command to specify the program in which to display man pages.

Question 34

What does the command **echo $variable** do?

Answer 34

Views the variable's value.

Question 35

What does the command **env** do?

Answer 35

Displays names and values only for environment variables applied to child sessions. In other words, variables that have been **export**ed.

Question 36

What does the command **set** do?

Answer 36

Sets or displays shell environment variables. Without options, displays names and values of all environment variables on the system.

Question 37

What does the command **unset variable** do?

Answer 37

Removes an environment variable.

Question 38

What does the command **VARIABLE=value** do?

Answer 38

Creates a user-defined environment variable.

Question 39

What does the command **export variable** do?

Answer 39

Exports a user-defined variable to make it available to child sessions.

Question 40

How do you append information to an existing environment variable?

Answer 40

To append information to an environment variable, put the current variable in the command. For example, **PATH=$PATH:/bin/***additionalpath*.