Question 1

Describe what file descriptors are, and then list three that can be used within the BASH shell, and discuss how they can be used.

Accepted Answer

Command input and output are represented by labels known as file descriptors. For each command that can be manipulated by the BASH shell, there are three file descriptors:
Standard input (stdin)
Standard output (stdout)
Standard error (stderr)
Standard input (stdin) refers to the information processed by the command during execution; this often takes the form of user input typed on the keyboard. Standard output (stdout) refers to the normal output of a command, whereas standard error (stderr) refers to any error messages generated by the command. Both stdout and stderr are displayed on the terminal screen by default.

Question 2

The ____________________ environment variable contains a list of directories to search for executable programs.

Accepted Answer

PATH

Question 3

A list of all exported environment and user-defined variables in a shell can be viewed with what command below?

Accepted Answer

A)   env
B)   set
C)   setenv
D)   getenv A

Question 4

The ability to extract, manipulate, and format text using pattern action statements belongs to which command below?

Accepted Answer

A)   sed
B)   grep
C)   awk
D)   nl

Question 5

​What two BASH environment variables represent the current working directory, and the absolute pathname of the current shell, respectively?

Accepted Answer

A)   ​PWD
B)   ​CWD
C)   ​PATH
D)   ​SHELL

Question 6

What environment file is always executed immediately after login for all users on the system, and sets most environment variables, such as HOME and PATH?

Accepted Answer

A)   ˜/.bash_profile
B)   ˜/.bash_login
C)   /etc/profile
D)   ˜/.profile

Question 7

In an if construct, what statements are optional?​

Accepted Answer

A)   ​fi
B)   ​elif
C)   ​else
D)   ​then

Question 8

What permissions are required to execute a shell script in a manner similar to any other executable program on the system?

Accepted Answer

A)   read
B)   write and read
C)   execute
D)   read and execute

Question 9

​Match each correct item with the statement below.​
a.​counter variable
b.decision construct​
c.​environment variables
d.​file descriptors
e.​hashpling
f.loop construct​
g.​redirection
h.Standard Error (stderr)​
i.​Standard Input (stdin)
j.Standard Output (stdout)
-​A special construct used in a shell script to alter the flow of the program based on the outcome of a command or contents of a variable. Common decision constructs include if, case, &&, and ||.

Accepted Answer

The answer of ​Match each correct item with the statement...

Question 10

What number represents the stdin file descriptor?

Accepted Answer

A)   0
B)   1
C)   2
D)   3

Question 11

Select the escape sequence that starts a new line when used with echo:

Accepted Answer

A)   ​\
B)   ​\a
C)   ​

D)   ​

Question 12

The default BASH shell prompt is set by an environment variable. What command can be used to view this variable?

Accepted Answer

A)   ls $PWD
B)   echo #PWD
C)   echo $PS1
D)   ls #PS1

Question 13

​What operator below is known as the NOT operator?

Accepted Answer

A)   ​-o
B)   ​-a
C)   ​!
D)   ​%

Question 14

Any command that can be executed on the command line can also be placed inside any environment file.

Accepted Answer

A) True 
 B)False

Question 15

What character is used to delimit most Linux configuration files?

Accepted Answer

A)   tab
B)   colon
C)   space
D)   semicolon

Question 16

Given the syntax command && command, the command on the left of the && construct is executed only if the command on the right of the && construct completed successfully.

Accepted Answer

A) True 
 B)False

Question 17

Explain the while construct, and demonstrate how it can be used.

Accepted Answer

The answer of Explain the while construct, and demonstrate how...

Question 18

The standard output and standard error from a terminal screen within the BASH shell can be redirected to a file on the filesystem using what shell metacharacter, followed by the absolute or relative pathname of the file?

Accepted Answer

A)   #
B)   
C)   >
D)   |

Question 19

Select the test statement that can be used to determine if A is numerically greater than B:

Accepted Answer

A)   [ A -g B ]
B)   [ A -ge B ]
C)   [ A -gt B ]
D)   [ A +eq B ]

Question 20

Select the escape sequence that is used for a form feed:

Accepted Answer

A)

B)   \f
C)   /f
D)   /n

Exam 7: Working With the Bash Shell