Shell Script Interview Question and Answers part 3 ?

1. How do you find out what’s your shell? echo $SHELL

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2. How do you fire a process in the background? ./process-name &

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3. How do you refer to the arguments passed to a shell script? $1, $2 and so on. $0 is your script name.

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4. What’s the conditional statement in shell scripting? if then … fi

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5. How do you do number comparison in shell scripts? -eq, -ne, -lt, -le, -gt, -ge

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6. How do you test for file properties in shell scripts?  -s filename tells you if the file is not empty, -f file...

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7. How do you do Boolean logic operators in shell scripting?  ! tests for logical not, -a tests for logical and, and ...

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8. How do you find out the number of arguments passed to the shell script?  $#

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9. What’s a way to do multilevel if-else’s in shell scripting? if then elif fi

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10. How do you write a for loop in shell? for in do done

11. How do you write a while loop in shell? while do done

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12. How does a case statement look in shell scripts? case in ) ;; ) ;; esac

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13. How do you read keyboard input in shell scripts? read

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14. How do you define a function in a shell script? function-name()

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15. How do you stop all the processes, except the shell window? kill 0

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16. How do you find out about all running processes? ps -ag

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17. How do you stop a process? kill pid

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18. What’s the command to find out today’s date? date

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19. What’s the command to find out users on the system? who

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20. How do you find out the current directory you’re in? pwd

21. How do you remove a file? rm

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22. How do you remove recursively? rm -rf

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23. How do you find out your own username? whoami

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24. How do you send a mail message to somebody? mail somebody@interviewduniya.com -s ‘Your subject’ -c ...

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25. How do you count words, lines and characters in a file? wc

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26. How do you search for a string inside a given file? grep string filename

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27. How do you search for a string inside a directory? grep string *

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28. How do you search for a string in a directory with the subdirectories recursed? grep -r string *

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29. What are PIDs?  They are process IDs given to processes. A PID can vary...

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30. How do you list currently running process? ps

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1. How to print nth column of a pattern/file without using awk,cut commands?


awk {print $n} < filename
where n is the field number


2.How to extract the second row of a text-file?

We can use either 
head -2 file.dat | tail -1 or 
cat file.dat | sed -n 2p > output.dat

sed -n 2p

3. Write a shell script that accept 7 numbers in loop?

Write a shell script that accept 7 numbers in loop,then make a sum of this numbers. Then count the numbers that are greater than 250 ?

Code


#!/bin/bash


total=0


c=0


for a in {1..3};


  do


        echo -n "Write a number : "


        read i


        if [ $i -ge 250 ] ; then let "c=c+1"


        fi


        let "total = i + total"


  done


echo "total = $total"


echo " > 250 = $c "

4. How would you print just the 25th line in a file ?

send -n 25 p

Code


head -n25 $filename |tail -n1

5. How would you get the character positions 10-20 from a text file?

   cat filename.txt | cut -c 10-20

   sed -n 25p file_name

   cut -c 10-20 filename

6.Shell script to add file extension

small shell script that adds an extension ".New" to all the files in a directory

ls -lrt | awk {priint "mv "$9" "%9".New"} | sh

Code

1. for i in *;
2. do mv $i $i.New;
3. done