Question

Ill. On the original UNIX file system, we are reading the file "/one/two/three .txt” All the directories fit in a single block each. 09

Answer 1

3) open()- This system call opens a file which is specified by the pathname. If there is no file with that particular name in the given path, it may create it optionally.

The open() system call returns a non-negative small integer, called as a file descriptor. This value will be used for other subsequent system calls, like read(),write(), etc.

This system call reads the information from the File Control Block and stores it in the open file table at system-wide, when a new file is accessed during the program execution.

syntax:

open(const char *pathname, int flags);

open(const char *pathname, int flags, mode_t mode);

pathname: Path of the file you want to open

flags must contain any one of the access modes: readonly,writeonly,read-write, etc.

mode: It allows you to give the permissions when the new file is created.

4) A symbolic link is a file which contains the path name for the original file. It can also refer to a pathname for which the file doesn't exists.

The following syntax must be used to create a symbolic link:

Syntax: ls -s <old> <new>

<new>- It is the new file name which contains the reference of the old one.

<old>- Here, you should specify a file name for which you want to create a symbolic link.

According to the given question, <new> is 'three' and <old> refers to '/one/two/three.txt'

Command to create the symbolic link for three.txt: ls -s /one/two/three.txt three

What is i-node?

Index-node is a datastructure which stores the following information:

• Size of the given file
• Devide ID, Group ID, User ID
• Mode of file and the access privileges given
• counter to find the number of hard links
• Protection flags for the file and time stamps when the file is created/modified etc.

The following commands will list the inode numbers for the files:

• ls -i :reads the names and inode numbers from the given directory.
• df -i : it is used to display the inode information of the file system.

5)

System crash during the inode creation:

A specific number of inodes will be kept aside when the file system is created. These are allocated only when required. i-nodes can be of 3 types:

• allocated- It is said to be allocated when it points to a file.
• unallocated- It is empty and doesn't point to any file.
• partially allocated- Here, the inode will be formatted incorrectly due to the system failure. Bad data will be written to the inode list.

  The following messages will also be seen:

• inodes should be repaired.

• error exists in inode.

System crash during the symbolic link creation: If a system crash occurs during the symbolic link creation, it may not be created or copied properly.