Lecture 02

Question 1

Give some properties of files and directories

Answer 1

• Owner
• Group
• Size
• Permissions (User, Group, Other)
• Times (Accessed, Modified, Changed (metadata))

Question 2

What functions are used to access the meta-data of files and directories.

Answer 2

stat, fstat, and lstat

Question 3

How is the file/directory metadata returned from the ‘stat’ function?

Answer 3

In a C structure called ‘stat’

Question 4

In a ‘stat’ structure, what is the name of the protection variable?

Answer 4

st_mode

This is a mode_t variable.

Question 5

Which macro function checks if a file is a regular file or not from a mode_t variable?

Answer 5

S_ISREG(m)

Question 6

Which macro function checks if a file is a directory or not from a mode_t variable?

Answer 6

S_ISDIR(m)

Question 7

Which macro function checks if a file is a block special file or not from a mode_t variable?

Answer 7

S_ISBLK(m)

Question 8

Which macro function checks if a file is a character special file or not from a mode_t variable?

Answer 8

S_ISCHR(m)

Question 9

Which macro function checks if a file is First In First Out or not from a mode_t variable?

Answer 9

S_ISFIFO(m)

Question 10

Which macro function checks if a file is a socket or not from a mode_t variable?

Answer 10

S_ISSOCK(m)

Question 11

Which macro function checks if a file is a symbolic link or not from a mode_t variable?

Answer 11

S_ISLNK(m)

Question 12

Do you need read permission on a file to call ‘stat’ on it?

Answer 12

No

Question 13

What permissions do you need to open a file?

Answer 13

Permissions on the file itself, along with ‘execute’ permission on every directory in the path.

Question 14

How many bits are used to represent permissions?

Answer 14

9.

Question 15

What are the three permission groups: User,..,..

Answer 15

User, Group, Other

Question 16

What do Unix systems use to store file and directory metadata?

Answer 16

inodes

Question 17

Do inodes contain filenames and contents?

Answer 17

No

Question 18

How are inodes addressed?

Answer 18

Via an index in the inode table. inode n is the nth inode in the table.

Question 19

Directories map _s to _s

Answer 19

names to inode numbers

Question 20

Where is the root directory ‘/’ stored?

Answer 20

In some known inode.

Question 21

Can you explicitly make a hard link to a directory?

Answer 21

No

Question 22

Can you explicitly make a hard link to a file?

Answer 22

Yes

Question 23

What are directory entries known as?

Answer 23

Hard Links

Question 24

What are symbolic links stored as instead of an inode?

Answer 24

A text string

Question 25

What is a symbolic link?

Answer 25

A special file that points to another file or directory

Question 26

What function is used to open a directory for reading?

What does it return?

Answer 26

opendir.

It returns a DIR*

Question 27

What is the function prototype for opendir?

Answer 27

DIR* opendir(const char *name);

Question 28

What function is used to read from a directory?

What does it return.

Answer 28

readdir.

It returns a struct dirent

Question 29

What is the function prototype for readdir?

Answer 29

struct dirent* readdir(DIR *dir);

Question 30

What two fields will every struct dirent have?

Answer 30

The inode number and the filename.

Question 31

What function gets the current working directory?

Answer 31

getcwd()

Question 32

What function changes the current working directory?

Answer 32

chdir()

Question 33

What directory is used as the root for relative file paths?

Answer 33

The current working directory

Question 34

Which function is used to change the owner of a file?

Answer 34

chown()

Question 35

Which function is used to change the permissions of a file?

Answer 35

chmod()

Question 36

Which function is used to change the group of a file?

Answer 36

chgrp()

Question 37

Which function is used to change the size of a file?

Answer 37

trucate()

Question 38

Which function is used to remove a directory?

Answer 38

rmdir()

Question 39

Which function is used to make a directory?

Answer 39

mkdir()

Question 40

Which function is used to create a link?

Answer 40

link

Question 41

Which function is used to delete a link?

Answer 41

unlink