Interview Questions:  - (Unix)

Unix :  -

Q) Write a single command to print your name one time?

Ans –

$ echo “Baishnab Charan Patra”

 

Q) Write a script to print your name 7 times?

Ans –

#! /bin/sh

a=0

while [ $a -lt 7 ]

do

echo “Baishanb Charan Patra”

a=`expr $a + 1`

done

 

Q) Write a script if a file is file type or not?

Ans –

#! /bin/sh

echo “Enter  a file name : “

read fn

if  [ -f $fn ]

then

echo “$fn is file type.”

else

echo “$fn is not file type.”

Fi

 

Q) What is the difference between $* and $@?

Ans –

$* -> Print all command line arguments passsed in a script.

$@ -> Print all command line arguments within double quotes individually passes in a script.

 

Q) What is $?, $# and $0? 

Ans –

$? ->  the exit status of last command.

$# -> total number of command line arguments

$0 -> the current script file name

 

Q) Top 5 processes using high CPU utilisation?

Ans –

$ top –c –b | head -5

Where –b = batch mode

Here you will see processes with command sorted as per their CPU usage.

or

$ top –b | head -5

Here you will see processes with commands along with their paths as per CPU usage.

-top command refresh in every 5 seconds.

or

$ ps -eo pid,ppid,%mem,%cpu,cmd --sort=-%cpu | head -5

where 

ps : To find process

-e : Select all processes.

-o : To customize a output format.

–sort=-%cpu : Sort the ouput based on CPU usage.

PID : Unique ID of the process.

PPID : Unique ID of the parent process.

%MEM : The percentage of RAM used by the process.

%CPU : The percentage of CPU used by the process.

Command : Name of the process.

 

Q) Top 5 processes using high memory utilisation?

Ans –

$ ps -eo pid,ppid,%mem,%cpu,cmd --sort=-%mem | head -5

ps : To find process

-e : Select all processes.

-o : To customize a output format.

–sort=-%mem : Sort the ouput based on memory usage.

PID : Unique ID of the process.

PPID : Unique ID of the parent process.

%MEM : The percentage of RAM used by the process.

%CPU : The percentage of CPU used by the process.

Command : Name of the process.

 

Q)  Command to print all directories inside a directory?

Ans –

$ ls –d

Or  (for long listing)

$ ls –ld

 

Q) Command to print the sum of file sizes in a directory?

Ans –

$ du –sch

Where s and c used to summarize and print a total size of all files recrusively.

h -> print in human readable format by default GB.

Or

$ du –scb

Where s and c used to summarize and print a total size of all files recrusively.

b -> prints in byte format.

 

Q) How to check if f1 and f2 are same file or not?

Ans –

$ diff f1 f2

If no output -> f1 and f2 are same.

If some output -> f1 and f2 are not same.

 

Q) How to check if last command/script we have ran, it went successful or not?

Ans –

$ echo $?

If output is zero -> command/script ran successfully.

If output  is non zero -> command/script ran unsuccessfully.

 

Q) How to remove duplicates in the file?

Ans –

$ awk ‘!a[$0]++’ file_name.txt > dont_dup.txt

 

Q) How to find largest size length sentence from a file?

Ans –

$ awk '{print NF, $0}' file_name | sort -nr | head -1