Understanding Linux file Types

Question 1

what does POSIX stand for?

Answer 1

POSIX = Portable Operation System Interface

Question 2

How many file types does the POSIX standard define?

Answer 2

7

Question 3

Which are the file types?

Answer 3

Regular

Directory

Sym link

FIFO

Block

Character

Socket

Question 4

What is the command to see a file’s type?

Answer 4

file

Question 5

what defines a file’s type?

Answer 5

what defines a file’s type is its magic number in the header and the #file command interprets this #

Question 6

How can you identify a regular file?

Answer 6

Regular files: denoted by a hypen - in ls -l

Question 7

What do regular files have?

Answer 7

they have a file name pointing to an inode which in turn points to a data block

Question 8

Can a regular file contain another file or directory?

Answer 8

No

Question 9

How can you identify a directory?

Answer 9

they are denoted by a d - in ls -l

Question 10

What do directories have within?

Answer 10

They have entries to other directories (sub dir) and other regular files

Question 11

Can hard links be a directory?

Answer 11

No

Question 12

Hard links are limited to the same what?

Answer 12

Hard links must be in the same inode table, meaning the same File system

Question 13

What do hard links have?

Answer 13

they have a file name pointing to an inode which in turn points to a data block, same as a regular file

Question 14

How can you identify a sym link?

Answer 14

in the output of ls -l, you will see a lowecase L

Question 15

For who can you create sym links?

Answer 15

Sym links can be created for files and directories as well

Question 16

Can sym links cross FS?

Answer 16

yes

Question 17

what does a sym link do?

Answer 17

they are a full path reference to another file o directory

Question 18

what perms do sym links have?

Answer 18

they have 777 perms

Question 19

what does FIFO mean?

Answer 19

FIFO pipe (first in - first out pipe)

Question 20

How can you identify a FIFO?

Answer 20

denoted by a p in the o/p of ls -l

Question 21

what command creates a FIFO file?

Answer 21

mkfifo

Question 22

What is an unamed pipe?

Answer 22

Unnamed pipes: such as ls -l | wc -l

they are a one-way communication between commands and you can pipe as many as you want/needed

Question 23

What is a named pipe?

Answer 23

so you can take a command and send its output to a pipe file, and then use that pipe file contents as stdin of another command
command to create a file that will work as a pipe is #mkfifo

Question 24

What is a socket for?

Answer 24

they are for bi-directional communication between local or remote systems

Question 25

What are the 2 types of block files?

Answer 25

block types (b) and character types (c)

Question 26

What are block types?

Answer 26

both types:

they represent hardware, but not network devices
they connect the kernel drives and the device

Question 27

What are block devices?

Answer 27

Block devices:

denoted by a b in the o/p of ls -l
usually disk devices which send data in blocks

Question 28

What are character devices?

Answer 28

Character devices:

sound cards, serial/parallel ports
they send data in characters