Unix Interview Questions and Answers

There are three types of permissions – owner, group and other (public), all of which can be listed using the command ls -l. Each user can have one or more of the following access – read (r), write (w), execute (x). Example, -rwxr-xr-- represent the file permissions for owner, members and everyone else as –

• Characters 2-4 (rwx) – means the owner has read, write and execute permission,
• Characters 5-7 (r-x) – indicates that the group has read and executed permission,
• Characters 8-10 (r--) – indicates that everyone else has only read permissions.

• cd – change directory
• pwd – current directory
• mkdir – create a new directory
• rmdir – remove an empty directory

Unix is an operating system that supports multitasking and multi-user capabilities. Unix provides a simple and user-friendly interface for users. It is the first OS to be written in high-level (C) programming language.

Unix is important:-

• Firstly, because of its design attributes from the initial release itself. That is, each complex task is divided into small, modular utilities that are easy to do.
• Secondly, during the initial internet boom, most web servers were UNIX machines from IBM, Sun, etc., hence making it a standard system for web servers.

The filter is a program that gets its data from the input stream and prints the results to the output stream. Examples – grep, sort, tail, head, cut, etc.…

The kernel is the central control of Unix. Kernel is the first part to be loaded when the OS loads and remains throughout the session. It executes processes, manages memory and handles interrupts and system calls. It provides drivers for controlling the hardware.

Unix can be installed on Windows 10 using VirtualBox, an open source virtualization tool.

• Download VirtualBox (https://www.virtualbox.org/wiki/Downloads) and create a virtual machine. Select memory and virtual hard disk requirements.

• Download the ISO image file from a reliable source.
• Install the distribution in the VirtualBox in seamless mode.

Alternatively, you can install Unix in dual boot.

Linux can be said as a clone of Unix with the following differences –

• It is a multi-user, multitasking system
• Uses kernel and shell to execute commands and complete tasks
• Hierarchical file system
• Easily portable to other machines as the code can be easily changed and compiled.
• Has pipes and filters to divide complex tasks into smaller utilities and then combine them.
• Application code is independent of the hardware vendor.

Continue reading our Unix interview questions list to know more about each of these features.

The different types of UNIX files are –

• ordinary files – text, data or program instructions.
• directories – stores regular and special files.
• special files – device files, used for input and output operations.
• pipes – temporary file that holds intermittent data until the second last command.
• sockets – allows advanced communication between several processes.
• symbolic links (soft links) – contains the path to another file (reference file)