Question { 1044 }

What is Unix, and how does it differ from other operating systems?

Answer

Unix is a multiuser, multitasking operating system designed for flexibility and adaptability. Unlike other operating systems like Windows, Unix is known for its stability, security, and support for networking. Unix systems use a hierarchical file system, support multiple users, and offer robust shell scripting capabilities. Unix also serves as the foundation for many other operating systems, such as Linux and macOS.

Question { 1176 }

What is the Unix file system hierarchy?

Answer

The Unix file system hierarchy is a structured arrangement of files and directories. The top level is the root directory, denoted by /. Important directories include:
• /bin: Contains essential command binaries.
• /etc: Contains system configuration files.
• /home: Contains user home directories.
• /usr: Contains user-installed software and utilities.
• /var: Contains variable data like logs and temporary files.
• /tmp: Used for temporary files.

Question { 1160 }

What is a shell in Unix? Name some common Unix shells.

Answer

A shell in Unix is a command-line interpreter that provides a user interface for interacting with the operating system. It processes commands entered by the user and returns the output. Common Unix shells include: Bash (Bourne Again Shell): The default shell for many Unix systems.
• Sh (Bourne Shell): The original Unix shell.
• Ksh (Korn Shell): An enhanced version of the Bourne Shell.
• Csh (C Shell): Known for its C-like syntax.
• Zsh (Z Shell): An extended version of Bash with more features.

Question { 1200 }

What are file permissions in Unix, and how are they represented?

Answer

File permissions in Unix control the access levels for files and directories. They determine who can read, write, or execute a file. Permissions are represented in a triplet format for the owner, group, and others (e.g., rwxr-xr--).
• r: Read permission.
• w: Write permission.
• x: Execute permission.
Permissions can also be represented numerically using a three-digit code, where each digit ranges from 0 to 7 (e.g., 755). The digits represent the sum of the permission values (4 for read, 2 for write, 1 for execute).

Question { 1156 }

How do you change file permissions and ownership in Unix?

Answer

• Changing Permissions: Use the chmod command to change file permissions. For example, chmod 755 filename sets the permissions to read, write, and execute for the owner, and read and execute for the group and others.
• Changing Ownership: Use the chown command to change the ownership of a file. For example, chown user:group filename changes the owner to user and the group to group.

Question { 1147 }

What is a Unix signal, and how do you handle them?

Answer

A signal in Unix is an asynchronous notification sent to a process to notify it of an event, such as an interrupt or termination request. Common signals include:
• SIGINT: Interrupt signal (usually sent by pressing Ctrl+C).
• SIGTERM: Termination signal, which can be caught and handled.
• SIGKILL: Forces a process to terminate immediately and cannot be caught.
Signals can be handled using signal handlers in shell scripts or programming languages like C.

Question { 1157 }

How do you find files in Unix?

Answer

The find command is used to search for files and directories in Unix. It can search based on various criteria, such as name, size, type, and modification time. For example, find /home -name "*.txt" searches for all .txt files in the /home directory.

Question { 1004 }

What is the difference between a hard link and a soft link in Unix?

Answer

• Hard Link: A direct pointer to the file’s data on the disk. Hard links share the same inode number as the original file and continue to exist even if the original file is deleted.
• Soft Link (Symbolic Link): A pointer to the file name rather than the file’s data. It is a separate file with its inode number. If the original file is deleted, the soft link becomes a dangling link, pointing to a non-existent file.