Unix Interview Questions & Answers
Showing 10 of 53 questions | Page 2
Unix technical interview questions and answers are frequently asked in system administration, DevOps, backend development, and support engineering roles. Unix forms the base for Linux and macOS, so companies expect candidates to understand file permissions, commands, shell scripting, process management, filters, pipes, and environment variables. Interviews in TCS, Infosys, Wipro, Cognizant, Capgemini, and Accenture often include Unix questions during both technical rounds and written tests. This guide explains frequently asked Unix commands and concepts using simple language, making it easy for freshers and experienced candidates to prepare. You can also download Unix interview questions PDFs and practice mock commands for better preparation.
Showing 10 of 53 questions
11. How can a parent and child process communicate?
A parent and child can communicate through any of the normal inter-process communication schemes (pipes, sockets, message queues, shared memory), but also have some special ways to communicate that take advantage of their relationship as a parent and child. One of the most obvious is that the parent can get the exit status of the child.
12. What is a zombie?
When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it - for example, the parent may need to check the child's exit status. To be able to get this information, the parent calls `wait()'; In the interval between the child terminating and the parent calling `wait()', the child is said to be a `zombie' (If you do `ps', the child will have a `Z' in its status field to indicate this.)
13. What are the process states in Unix?
As a process executes it changes state according to its circumstances. Unix processes have the following states:
Running : The process is either running or it is ready to run .
Waiting : The process is waiting for an event or for a resource.
Stopped : The process has been stopped, usually by receiving a signal.
Zombie : The process is dead but have not been removed from the process table.
14. What Happens when you execute a command?
When you enter 'ls' command to look at the contents of your current working directory, UNIX does a series of things to create an environment for ls and the run it: The shell has UNIX perform a fork. This creates a new process that the shell will use to run the ls program. The shell has UNIX perform an exec of the ls program. This replaces the shell program and data with the program and data for ls and then starts running that new program. The ls program is loaded into the new process context, re
15. What is 'ps' command for?
The ps command prints the process status for some or all of the running processes. The information given are the process identification number (PID),the amount of time that the process has taken to execute so far etc.
16. How would you kill a process?
The kill command takes the PID as one argument; this identifies which process to terminate. The PID of a process can be got using 'ps' command.
17. What is an advantage of executing a process in background?
The most common reason to put a process in the background is to allow you to do something else interactively without waiting for the process to complete. At the end of the command you add the special background symbol, &. This symbol tells your shell to execute the given command in the background.
Example: cp *.* ../backup& (cp is for copy)
18. How do you execute one program from within another?
The system calls used for low-level process creation are execlp() and execvp(). The execlp call overlays the existing program with the new one , runs that and exits. The original program gets back control only when an error occurs.
execlp(path,file_name,arguments..); //last argument must be NULL
A variant of execlp called execvp is used when the number of arguments is not known in advance.
execvp(path,argument_array); //argument array should be terminated by NULL
19. What is major difference between the Historic Unix and the new BSD release of Unix System V in terms of Memory Management?
Historic Unix uses Swapping entire process is transferred to the main memory from the swap device, whereas the Unix System V uses Demand Paging only the part of the process is moved to the main memory. Historic Unix uses one Swap Device and Unix System V allow multiple Swap Devices.
20. What is the main goal of the Memory Management?
It decides which process should reside in the main memory,
Manages the parts of the virtual address space of a process which is non-core resident,
Monitors the available main memory and periodically write the processes into the swap device to provide more processes fit in the main memory simultaneously.