Lesson 2

Question 1

What is the shell?

Answer 1

A program that enables text based communication between the OS and the user

Question 2

Name a few popular shells

Answer 2

BASH, csh, ksh, zsh

Question 3

Describe the basic command line structure for a command

Answer 3

command <options> <arguments></arguments></options>

Question 4

What are internal shell commands?

Answer 4

Built into the shell itself, things like echo, exit and cd

Question 5

What are external shell commands?

Answer 5

Reside in binary files added to the PATH variable

Question 6

What does the type command do?

Answer 6

Shows where the binary is located if external command or shows if it’s built in shell command

Question 7

What do double quotes tell the shell?

Answer 7

To use the text in between the “…” as regular characters. All special characters lose their meaning except $ and \

Question 8

What do single quotes tell the shell?

Answer 8

They revoke any special characters, it will take the string as a literal

Question 9

What do escape characters tell the shell?

Answer 9

To remove special meaning of certain characters, for example $ removes the builtin meaning on $

Question 10

How could you with touch create a file 5 times with one command?

Answer 10

Using the {..} operator… touch foo{1..5}

Question 11

With rm how can you delete all files matching a pattern?

Answer 11

rm foo? deletes anything with foo and 1 additional character

Question 12

When creating a local variable how can you access it’s value?

Answer 12

using echo and then $…so echo $foo

Question 13

How to remove a local variable?

Answer 13

With the unset command

Question 14

How can you make a local variable global?

Answer 14

By using the “export” command

Question 15

What is the PATH variable?

Answer 15

stores a list of directories separated by a colon that contains executable programs eligible as external commands to the shell

Question 16

what does the which command do?

Answer 16

Shows the path to where the binary is stored

Question 17

What is the command for creating a time variable?

Answer 17

date for timezone TZ=GMT date or EST

Question 18

what does the wc command do?

Answer 18

used to find out the number of newline count, word count, byte and character count in the files specified by the File arguments to the standard output and hold a total count for all named files.

Question 19

What does the –help command do?

Answer 19

Most command have a –help option but it’s normally pretty brief and limited

Question 20

What does the man command do?

Answer 20

man displays a manual for a given command like man mkdir

Question 21

If something has more than 1 man page, how do you need to refer to it?

Answer 21

Using the category syntax, example passwd(1) vs passwd(5)

Question 22

What is the difference between man and info?

Answer 22

info is normally more detailed than man pages and are formatted in hypertext.

Question 23

What does the locate command do?

Answer 23

Quickly locates anything matching a given string in the file system. Also supports wildcards for pattern matching, for example astericks

Question 24

How does find differ from locate?

Answer 24

find searches a directory tree recursively, it doesn’t maintain a database like locate, but it does support wildcards

Question 25

what does updatedb command do?

Answer 25

updates the locate command database

Question 26

when running ls -lh will the directory sizes be correct?

Answer 26

No because directories are always shown as 4096 bytes, this is the size of the link

Question 27

What is globbing?

Answer 27

Globbing is a simple pattern matching language. Linux shells use this language to refer to groups of files whos names patch a specific pattern

• matches any number of characters
  ? matches 1 character (not numbers)
  [] matches a class of characters

Question 28

what does -v do for mkdir, rm and cp?

Answer 28

Turns on verbose output mode

Question 29

What happens if you move the mv command to move a directory into itself?

Answer 29

You will get an error message that it is a subdirectory of itself

Question 30

how would you delete all files starting with “foo” in a directory?

Answer 30

rm foo*

Question 31

Using cp, how can we have the copied file retain the permissions and modification time of the original?

Answer 31

By using the -p or –preserver options

Question 32

When using mv how can you prevent overwriting files?

Answer 32

By using -n or –no-clobber