Unix / Linux Interview Questions

Shell is an interpreter. It interprets the commands and submits for execution.

Bsh, csh, ksh and bash.

It is a short cut to the file or directory. ln is the command used for the same.

Solaris.

It interacts with hardware and most of the tasks like memory management, tash scheduling and file management.

Login program.

passwd.

Link count.

Command − logout / ctrl+d / command − exit

shutdown.

Yes.

reboot.

No, Linux is open source.

Redhat, Cent OS, Debian, Ubuntu and Fedora.

First.

A file/directory name beginning with. (dot) is considered as hidden one.

Ken Thompson

C

AT & T Bell labs.

The terminal associated with the respective login.

man

which

* And ?

0

A pathname is absolute if it is described in relation to root, so absolute pathnames always begin with a /. A pathname if it is relative to your current working directory is called as relative path. Relative pathnames never begin with /

Having an execute permission on a directory means to have traverse permission.

PS1

lp/lpr

A running instance of a program is called as a process.

vi − R

k, j, h and l

Yanking is the process of holding the cut or copied text into the buffer which can pasted.

:set nu

A first line in the shell script which tells which shell need to be used to execute the following commands in the shell script.

chmod

By prefixing the dollar ($) symbol for the shell variable.

unset.

$0

0

$?

expr

−f

Enclose the command in back quotes and assign it to a variable.

A here document is used to redirect input into an interactive shell script or program.

return

No, it is a convention.

sh <file>

Globally search for regular expression.

cut

Concatenation of files text.

OS assigns an unique process identification number for the currently executing processes is called as process-id (PID).

useradd

To connect to remote UNIX/Linux machine.

kill

To search for a file/files.

head.

UNIX

It give the process to have the privileges of the owner of the file during the instance of the program.

The process is dead but have not been removed from the process table.

Yes

It contains a program called MBR (Master boot record) which load the kernel as the part of the system booting.

alias

echo −e “text”. Option –e places the cursor on the same line

‘diff’ shows all the differences from two file whereas ‘cmp’ shows the only the first occurring difference. The said is applicable only if differences between the files do exist.

Place the commands connected with pipes (|).

Still the current working directory would be /

It the directory through which date I/O happen on to/from a device.

HOME.

ls −a

df

To execute a command/commands at a specific time.

Will receive the mail of the same.

LILO means linux loader, which loads the kernel into memory and starts the OS.

Double the RAM size.

ls −l|grep “^d”

uname

grep −c “pattern” <file>

To keep the command running even after the user who issues the command has logged out.

For UNIX/Linux every device is a file and are typically located in the directory /dev.

A file is given a unique number by OS and is called as inode.

Crontab

chmod

mv

4, 2 & 1 respectively for r, w & x.

Ampersand (&)

ps −e

tty

Shell built in commands are called as internal commands.

init s

write

UMASK is a Unix environment variable, which automatically sets file permissions created files.

022

UNIX File system.

Journal File System

Linus Torvalds

head −<n> file.txt | tail −1

while, until & for.

/home

/root

root