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Linux+ > 1.3 Environment Variables > Flashcards

1.3 Environment Variables Flashcards

2
Q

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

A

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

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3
Q

What are the two different types of variables?

A

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

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4
Q

What is a user-defined variable?

A

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

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5
Q

What is an environment variable?

A

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.

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6
Q

What is the standard for environment variable names?

A

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

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7
Q

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

A

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

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8
Q

What is a user-defined variable?

A

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

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9
Q

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

A

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

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10
Q

How do you make user-defined environment variables persistent?

A

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

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11
Q

What does the BASH environment variable contain?

A

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

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12
Q

What does the SHELL environment variable contain?

A

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

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13
Q

What does the CPU environment variable contain?

A

The CPU environment variable contains the type of CPU.

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14
Q

What does the DISPLAY environment variable contain?

A

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

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15
Q

What does the ENV environment variable contain?

A

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

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16
Q

What does the EUID environment variable contain?

A

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

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17
Q

What does the HISTFILE environment variable contain?

A

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

18
Q

What does the HISTSIZE environment variable contain?

A

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

19
Q

What does the HISTFILESIZE environment variable contain?

A

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

20
Q

What does the HOME environment variable contain?

A

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

21
Q

What does the HOST environment variable contain?

A

The HOST environment variable contains the name of the computer.

22
Q

What does the HOSTNAME environment variable contain?

A

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

23
Q

What does the INFODIR environment variable contain?

A

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

24
Q

What does the LOGNAME environment variable contain?

A

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

25
Q

What does the MAIL environment variable contain?

A

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

26
Q

What does the MANPATH environment variable contain?

A

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

27
Q

What does the OLDPWD environment variable contain?

A

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

28
Q

What does the OSTYPE environment variable contain?

A

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

29
Q

What does the PATH environment variable contain?

A

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.
30
Q

What does the PS1 environment variable contain?

A

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

31
Q

What does the PWD environment variable contain?

A

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

32
Q

What does the LANG environment variable contain?

A

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

33
Q

What does the PAGER environment variable contain?

A

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

34
Q

What does the command echo $variable do?

A

Views the variable’s value.

35
Q

What does the command env do?

A

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

36
Q

What does the command set do?

A

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

37
Q

What does the command unset variable do?

A

Removes an environment variable.

38
Q

What does the command VARIABLE=value do?

A

Creates a user-defined environment variable.

39
Q

What does the command export variable do?

A

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

40
Q

How do you append information to an existing environment variable?

A

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

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