Shell Scripting & Linux Interview Questions for DevOps Engineers | Bash Zero to Hero |

[@VDenys]

0:47 List some of the commonly used shell commands ? 3:18 Write a simple shell script to list all processes 5:30 Write a script to print only errors from a remote log 9:52 Write a shell script to print numbers divided by 3 & 5 and not 15 19:24 Write a script to print number of "S" in Mississippi 23:36 How will you debug the shell script? 23:59 What is crontab in Linux? Can you provide an example of usage? 24:58 How to open a read-only file? 25:24 What is a difference between soft and hard link? 28:05 What is a difference between break and continue statements ? 30:58 What are some disadvantages of Shell scripting? 31:45 What a different types of loops and when to use? 32:19 Is bash dynamic or statically typed and why? 33:23 Explain about a network troubleshooting utility? 35:06 How will you sort list on names in a file ? 35:43 How will you manage logs of a system that generate huge log files everyday? "I think it will be convenient, give it a like."

[@tapasghosh9802]

good job denys. I appreciate

[@shivanipatil745]

thank yo so much

[@nikhilnirbhavane1005]

Thank you Abhishek !! :) Questions which I faced in interview that people should be aware of. 1) what is sticky bit in linux 2) how do we verify if out shell script is executed successfully? 3) what is the flag to check if file is empty or not? 4)What is positional parameter ? 5)what is command substitution? 6)How do you set crontab? 7) how will your .sh script configured in CRONTAB will run when system is restarted?

[@Deva2596]

Thanks for posting:)

[@tapasghosh9802]

Hey nikhil ..thanks for sharing

[@SathyaManikanta]

Sure, let's go through each of these interview questions one by one with explanations. ### 1. What is a Sticky Bit in Linux? The sticky bit is a special permission that can be set on directories. When the sticky bit is set on a directory, only the owner of the directory, the owner of the file, or the root user can delete or rename the files within that directory. #### Example To set the sticky bit on a directory: ```bash chmod +t /path/to/directory ``` To check if the sticky bit is set: ```bash ls -ld /path/to/directory ``` You will see a `t` at the end of the permissions: ``` drwxrwxrwt 2 root root 4096 Jul 1 12:34 /path/to/directory ``` ### 2. How Do We Verify if Our Shell Script is Executed Successfully? The exit status of a command can be checked using the special variable `$?`. A zero exit status (`0`) indicates success, while a non-zero value indicates failure. #### Example ```bash #!/bin/bash your_command if [ $? -eq 0 ]; then echo "Command executed successfully" else echo "Command failed" fi ``` You can also use the `set -e` option at the beginning of your script to exit the script immediately if any command returns a non-zero status. ### 3. What is the Flag to Check if a File is Empty or Not? The `-s` flag in the test command (`[ ... ]`) checks if a file is not empty. #### Example ```bash #!/bin/bash file="path/to/yourfile" if [ -s "$file" ]; then echo "File is not empty" else echo "File is empty" fi ``` ### 4. What is a Positional Parameter? Positional parameters are variables that hold the arguments passed to a shell script or function. They are referenced using `$1`, `$2`, `$3`, etc., where `$1` is the first argument, `$2` is the second, and so on. `$0` refers to the script or command itself. #### Example ```bash #!/bin/bash echo "First argument: $1" echo "Second argument: $2" ``` ### 5. What is Command Substitution? Command substitution allows you to capture the output of a command and use it as an argument in another command. It can be done using backticks (\`) or `$(...)`. #### Example Using backticks: ```bash current_date=`date` echo "Current date is $current_date" ``` Using `$(...)`: ```bash current_date=$(date) echo "Current date is $current_date" ``` ### 6. How Do You Set Crontab? Crontab is used to schedule commands to be executed periodically. You can edit the crontab file for your user by running: ```bash crontab -e ``` This will open an editor where you can add your cron jobs. The format is: ``` * * * * * command_to_be_executed ``` The fields represent: 1. Minute (0 - 59) 2. Hour (0 - 23) 3. Day of month (1 - 31) 4. Month (1 - 12) 5. Day of week (0 - 7) (Sunday is 0 or 7) #### Example To run a script every day at 2 AM: ```bash 0 2 * * * /path/to/your_script.sh ``` ### 7. How Will Your .sh Script Configured in CRONTAB Run When the System is Restarted? To ensure a script runs at startup, you can use the `@reboot` cron directive. #### Example To add a script that runs at system startup: ```bash @reboot /path/to/your_script.sh ``` This entry in the crontab will execute `your_script.sh` every time the system boots up. ### Summary 1. **Sticky Bit**: Special permission on directories preventing users from deleting or renaming files they do not own. 2. **Verify Script Execution**: Check `$?` for the exit status of the last command. 3. **Check If File is Empty**: Use `-s` flag. 4. **Positional Parameter**: Variables holding script arguments, accessed via `$1`, `$2`, etc. 5. **Command Substitution**: Capturing command output using `$(...)` or backticks. 6. **Set Crontab**: Use `crontab -e` to schedule jobs. 7. **Run Script at Startup**: Use `@reboot` in crontab. These are some essential Linux concepts and commands that can help in understanding and managing a Unix-like environment efficiently.

[@sindhudevapati6583]

@@SathyaManikanta Thank you for providing the answers.

[@pujabaidya5822]

Thanks ​@@SathyaManikanta for the answers

[@Deva2596]

### Summary: - [00:01] 🎯 Understanding and mastering shell scripting interview questions involves a structured approach, starting from basics and building up to advanced topics. - [01:12] 💼 Interviewers often begin by asking about **commonly used shell commands** to gauge your practical familiarity with scripting in daily tasks. - [04:15] 📜 **Demonstrating simple shell scripts**, such as **listing all processes**, showcases your ability to work effectively on Linux systems. (`ps -ef` ) - [06:30] 🛠 Using the `curl` command and piping output to `grep` allows you to fetch and filter specific lines from remote log files. - [09:03] 🔢 Crafting scripts to manipulate numbers based on conditions, like divisibility by 3, 5, and exclusion of 15, demonstrates algorithmic thinking. - [11:01] 🖋 Writing scripts step-by-step, explaining each segment as you build, showcases your clarity of thought and logical progression. - [14:31] 🔄 Employing for loops to iterate through a range of numbers, combining with logical conditions, allows effective script control. - [19:08] 🔠 Manipulating strings like counting occurrences of a specific character ("s" in "Mississippi") highlights your ability to process and analyze textual data in scripts. - [21:40] 📜 The `grep` command with `o` option filters text for specific patterns. - [22:05] 📜 `wc -l` counts lines in a file; used in conjunction with `grep`. - [22:46] 📜 Combine `grep` and `wc` to filter and count specific patterns. - [23:13] 📜 Practice is crucial to mastering shell scripting techniques. - [24:09] 📜 Cron tab automates tasks, scheduling scripts to run at specific times. - [25:04] 📜 Use `-r` option to open a file in read-only mode with `vim`. - [25:32] 📜 Differentiate between soft links and hard links; understand use cases. - [28:08] 📜 Explain the concepts of `break` and `continue` statements in loops. - [30:59] 📜 Address disadvantages of shell scripting, focusing on practical scenarios. - [31:54] 📜 Understand the types of loops (for, while, do-while) and their use cases. - [32:20] 📜 Shell scripting is dynamically typed; differences from statically typed languages. - [33:32] 📜 Utilize `traceroute` and `tracepath` commands for network troubleshooting. - [34:01] 📜 Use the `sort` command for sorting and listing names in files. - [35:10] 📜 Employ `logrotate` to manage and maintain large log files efficiently. - [36:22] 📜 Explain how `logrotate` helps manage logs generated by applications.

[@dilshan181]

Thank you

[@tapasghosh9802]

good job deva. I appreciate

[@suryasurya-tj6gu]

Abhishek, Can you please start Shell Scripting in advance level. You are the best mentor.

[@SathyaManikanta]

19:25 few ways of doing it Method 1: Using grep Command #!/bin/bash x=mississippi # Count occurrences of 's' using grep echo "$x" | grep -o "s" | wc -l Method 2: Using tr command #!/bin/bash x=mississippi # Count occurrences of 's' using tr echo "$x" | tr -cd 's' | wc -c Explanation: tr -cd 's': Translates and deletes all characters except 's', leaving only 's' characters. wc -c: Counts the number of remaining characters, which corresponds to the number of 's' in the string. Method 3 : Using awk #!/bin/bash x=mississippi # Count occurrences of 's' using awk echo "$x" | awk -F's' '{print NF-1}' Explanation: awk -F's' '{print NF-1}': -F's' sets the field separator to 's'. NF is the number of fields, which would be the number of parts the string is divided into by 's'. NF-1 gives the number of 's' in the string.

[@maduboy4898]

You are the best teacher I have ever learned . I am from sri lanka and . I started learning devops in just 3 days . I gain a lot of knowledge from you . Thank you boss

[@AbhishekVeeramalla]

☺️☺️

[@SRG-n3d]

Awesome,wonderful 3 videos session on shell scripting. By practicing all these we will get confident on scripting. Thank you.

[@AbhishekVeeramalla]

😍😍

[@mynameisram6795]

Really superb In youtube i have never seen this type of shellscripting, i really liked this class.

[@AbhishekVeeramalla]

Thanks Ram

[@sayyedrabbani972]

Done with shell scripting moving ahead thankyou @abhishek anna for making the concepts easy.

[@vikas9890]

Watched all 3 sessions. It was fantastic crisp and clear. Thanks a lot sir and please make some more.

[@AbhishekVeeramalla]

Thank you, I will

[@HarishKumar-e5h7h]

completed all three videos in shell script i have to practice once again to get confidence thanks abhisheik

[@AbhishekVeeramalla]

Great!

[@bollurahul]

very well explained abhishek. I never wrote a shell script so far being an experienced DevOps engineer but after watching your videos, my confidence levels boosted in a way that from now on even I also will start writing the shell scripts. thanks a lot for your videos and hoping for more upcoming videos that will help lot of people. best wishes!!

[@AbhishekVeeramalla]

Glad to hear that

[@Aakash-xm8eu]

hey Abhishek, I had tried shell script in my 2nd year at college and didn't get it but now i am feeling very comfortable and looking forward for a great knowledge about devops

[@TheSeeker001]

Hi Abhishek, that's very interesting to know these interview point of view questions. That's very informative. Please do more of these. Part -3 of Shell Scripting done :)

[@amolbar]

Very useful information you have provided in this session. You are doing great job. Your teaching style is very good.

[@AbhishekVeeramalla]

Most welcome !!

[@barathamudha2607]

@@AbhishekVeeramalla nice teaching bro easy to understand as a begginer thank you for making this session for free

[@IT_Wala_Rups]

Hi @Abhishek Veeramalla, Really you are a great mentor, teacher, trainer, expert & all for Cloud, Linux & DevOps domain. Thanks for such great sessions for free. Thanks keep it up bhai!

[@AbhishekVeeramalla]

You are most welcome

[@subiksha1278]

@@AbhishekVeeramallapls do more videos on shell scripting advanced

[@nainabhartia9260]

You teach with such patience and love !

[@PrachiBhoj-k8v]

Thank u so much abhishek for providing such a wonderful content

[@AbhishekVeeramalla]

My pleasure 😊

[@aravindreddy1303]

Hi @Abhishek.Veeramalla , Thanks for your first two videos and for this video. I would like to see more of it in relation to the Devops Engineer. You are good at what you are doing. Keep going and I wish you all the best. Thanks

[@AbhishekVeeramalla]

Thanks for the feedback

[@koti3228]

The way u r teaching is really good and coming to shell scripting,as a devops engineer where and when we use in our daily activities in the real time please make a video on that so it could help....Thankyou bro

[@AbhishekVeeramalla]

Thanks

[@koti3228]

@AbhishekVeeramalla Do you have any more scenario based on shell scripting..if u have please share..Thanks bro

[@PriyaLuckyThakkar]

Hey Abhishek first of all loads of thanks, i really appreciate what ur doing and i really understand it so well, ur way of explaining concept is outstanding, i am very much new to this devOps world but because of u im finding little ease thanks a lot

[@faizakashaf805]

thanks abishek for such a nice video

[@niroopbs]

Thank you so much for sharing the knowledge. You have covered almost everything in this video.

[@shaikzilanbasha6132]

25:20 how to open a read-only file, kindly note we need to use vim - R text.sh it will open in read-only mode. -r showing like No Swap file found for file Please don't mind for my correction I'm practicing all your videos

[@karanjaggi4083]

Thanks abhishek for such a wonderful content

[@abhishekgowda7383]

i have watched this complete playlist,it is really helpful,thank u broh,keep posting content like this..

[@AbhishekVeeramalla]

Welcome

[@RC_CarRacing]

Very nicely explained…thanks!

[@ravipanavi]

Hi Abhi, Kindly continue the Advance Shell scripting videos TQ

[@AbhishekVeeramalla]

sure, noted

[@vikasthakur6513]

Yes, please and if possible please make videos on ansible as well. Thank you Sir dil se.

[@pothugangireddy6339]

You have good teaching skills sir... thank you for educating us keep posting videos sir !

[@AbhishekVeeramalla]

Thank you, I will

[@jaydave1284]

Hey Man, very nice video. Also you should explain earlier in the first session about "test" " [ " and club it together with the syntax with if [ expression ], this will give more idea to people why there's space between expression and [ .

[@SumitBudhawant]

Thanks a lot Abhishek!!

[@SATYANARAYANA-i1d]

thank you wonderful Video, I think in advanced shell scripting we can see some automation and best practices on cron job and log rotates !

[@AbhishekVeeramalla]

👍

[@abdurahmanfaisal6835]

Thanks Abhishek, doing so much effort for free. Really appreciate 🙏🏻

[@KalpanaRadhakrishnan1999]

Tq so much abhishek veeramalla😊😊😊😊😊

[@AbhishekVeeramalla]

❤️

[@sowmiyabaskar7089]

Thanks for your Video ..explained everything in a simple way which makes us to understand well

[@AbhishekVeeramalla]

awesome

[@MdAshraf007]

It should be "vi -R " to open it in read mode.

[@ausafumarkhan5363]

Correct 😊

[@subiksha1278]

@AbhishekVeeramalla pls do more series on Advanced shell scripting.. much needed.

[@AbhishekVeeramalla]

Sure

[@prithvivishwanath]

completed today .... i am confident i will crack shell scripting and devops interviews questions .. thanks - Abhi

[@AbhishekVeeramalla]

Wow 😍😍

[@Anilsree-06]

This is very interesting and most useful one, once again Thanks Abhishek for your time and help.

[@AbhishekVeeramalla]

Thanks !!

[@mejavedjaved]

Date- 20-08-2024 . Completed the video and it is very easy to follow. You're an awesome tutuor/Guru or what to name you. Thank you.

[@Al_arabian]

Thankyou so much with your explanation and teaching skills shell scripting concepts is clear for me ❤️❤️❤️

[@AbhishekVeeramalla]

Happy to hear that!

[@AmrutaWagh-kb3yv]

really great abhishek sir ji 👍🏻

[@AbhishekVeeramalla]

thanks

[@utkarshtenguria3836]

the session was amazing thanks

[@saurabhjain8904]

Sir u r great, want to learn devops from you

[@AbhishekVeeramalla]

Sure

[@dummymail6029]

great video thanks a lot :) ahishek

[@vasujhawar.6987]

5:15 No need of Field delimitter -F as awk has whitespace as Field seperator by default.

[@apurva6234]

Hello vasu, from where can I learn bash scripting apart from this, can you please suggest?

[@vasujhawar.6987]

@@apurva6234 basics are enough, read documentation and do questions regularly, there are many free and cheap resources on internet.

[@vasujhawar.6987]

@@apurva6234 And I also landed on your channel, and found few music playlists. I was just curious, that did you made them by yourself, all perfectly curated.

[@apurva6234]

​@vasujhawar.6987 I'm glad you liked it. Yes, I made those myself. :) ​

[@apurva6234]

​@@vasujhawar.6987 , also thanks! I'll go through the documentation

[@santhoshar8816]

such a awsome explaination abhi sir 😍😍

[@sathishdarshanala6137]

thanks abisheck learnt a lot from your videos

[@AbhishekVeeramalla]

Awesome

[@pothugangireddy6339]

any way your video's very useful for me, Thanks, Thanks,Thank you so much Dude !💝

[@AbhishekVeeramalla]

You are welcome!

[@nagajanardhanmunaganuri430]

1.Thanks for the video , i have question , if application is getting down or getting 404 .. 300 ..etc what should we cheked in logs ..means as application logs or apache logs or gc.logs or error.logs can please explain us for each log like what uses of logs. If you make it a video it will more help to us . 2.Can please explain me apache rules like inbound and outbound some says that in real-time do white list end point in outbound /inbound 3. Confluence page like user jornny make simple example 4. Can pleas exaplane the urca calls like request-out and response-in logs in monitering tools like splunk or other tools

[@harshithavaddi672]

9:52 Write a shell script to print numbers divided by 3 & 5 and not 15? in this question i am not getting the proper output

[@surajdevv]

Completed day 7 of journey 😊

[@sahapriyanka86]

@Abhishek.Veeramalla please do a detailed video on advanced shell scripting including loops

[@Zeliebenard639]

very explicit, 👏

[@AbhishekVeeramalla]

❤️

[@DSD9Talent]

Sorry to say but this is true, Nowadays no interviewer ask such straight question, all come with scenario base questions, this wont work for me at all

[@AbhishekVeeramalla]

This is for beginners.

[@amarthyasai17]

Where can i learn scenario based questions? Is there any source? pls share

[@deepak8914]

Hi can you post list of command which you used in this playlist, its esay to refer from git repository, I am followed your AWS series it's very nice document you maintain

[@ChinnaDornadula]

Great❤

[@thotapraveenbabu]

U have good teaching skills sir... thank you for educating us keep posting videos sir

[@AbhishekVeeramalla]

Thank you, I will

[@rakshithhs757]

subscribed, How well you will explain,thak you

[@AbhishekVeeramalla]

Welcome

[@arundhathidanda7640]

Can you please make videos on powershell scripting aswell

[@AbhishekVeeramalla]

Hi, I will try

[@Divyaperuri]

Hi Abhishek , Please do the videos on Shell Scripting in advance level also.

[@barathamudha2607]

thanks a lot making this video

[@AbhishekVeeramalla]

You're welcome 😊

[@SANDESHPAI-v3p]

on 18:16 I have a doubt I have followed all that but it is not executing it.. Please could you tell it!!!

[@smmrok]

Same here

[@AbhishekPandeySunny]

You may not have set the right file permission. What is the error you're getting?

[@AshokKumar-kl4et]

Worth spending time in this

[@AbhishekVeeramalla]

🙏

[@AjayKumar-rz6hz]

Thank you very much for such helpful vedios to prepare for the interview. I have a second round tomorrow for Devops . Could you please guide me which one should I watch

[@AbhishekVeeramalla]

Hey, That's awesome .. All the best It depends on the JD. I think we have covered most of the scenarios and tools. So checkout the playlists

[@bikramsingh9416]

Thanks, its too good session Can you share any example video or script related to logrotate.

[@venkateshmekala7321]

Hi Abhishek Can you do the Powershell Videos also and it will be helpful lot of people

[@AbhishekVeeramalla]

Will try

[@skk-dq4kb]

18:58 correction in shell script above shell script is not working even its not throwing error correct ans is #!/bin/bash ########### # Author: Soham # Date: 23 May 2024 # This script will give the numbers divisible by 3 or 5 but not divisible by 15 ########### for i in {1..100}; do if (( (i % 3 == 0 || i % 5 == 0) && i % 15 != 0 )); then echo $i fi done

[@Rakeshcloudops]

question i was asked during my interview about linux was what is a zombie process

[@swapnilkhandekar4157]

Here the solution ,A zombie process, also known as a defunct process, is a terminated process that has not been fully removed from the process table. It exists in this state until the parent process acknowledges its termination and collects its exit status. Zombie processes consume minimal system resources but still occupy an entry in the process table. { Writing for myself }

[@ashishpandey8766]

Thanks, Abhi

[@skyhigh7424]

Very good content

[@AbhishekVeeramalla]

Thanks

[@MutyalaPardhasaradhi]

Abhishek bro, please start a advance to hero shell scripting videos

[@mullapudirajaram796]

Anna i would like to ask you do on this flow don't stop inbetween 😢 regarding shell scripting

[@AbhishekVeeramalla]

I did live project as well. Please check the playlist for shell scripting

[@HaseenaSA-wx4mi]

Make video on advanced shell script commands and trap in details

[@timtom3403]

can someone please explain why we got that at 7:00 along with intended the grep result

[@manupriyar8169]

Hi Abhi,, done with shell scriptibg course from your playlist.. You can help us more in it.. Thanks once again❤

[@gummadinagalaskhmi]

Can you please do the series for powershell too

[@manojtalluri5087]

good one

[@AbhishekVeeramalla]

Thanks !!

[@ashwinswain1649]

Hello Abhishek can you help with how to write Github action workflow to run my bash script which extracts tls key and secret and in the workflow it will also include steps to save those files on github repo folder

[@AbhishekVeeramalla]

Noted

[@naniadabala53]

Can you please make advanced level shell scripting videos❤

[@lekkalanaveenkumarreddy1539]

hello ,the video was nice but i kinda felt like you were rushing it, if its possible can you explain all the networking commands and other scripts in detail

[@shivamgupta8076]

Hi Abhishek, Even I have typed the same commands for the question (number divisible by 3, 5 not 15). While running the file, nothing is printed. All the 777 permissions are given, but till no output. Any suggestions?

[@naniadabala53]

same for me, did you find out the error?

[@SaiRoop_DanceSpot]

The question which have here - Write a shell script to print numbers devided by 3 AND 5 and not 15. i feel the question its self is wrong it should be number devided by 3 OR 5 and not by 15. Am i right? Please correct me if i am wrong

[@suvarnadhavala0124]

Hi Abhishek Thanks for the sessions... i have a query.. whatever scripts i give and execute, i see the same command not found error. tried installing a couple of things as per google. still see the same error.. please help!!!

[@AbhishekVeeramalla]

If u r running these commands or script in your windows machine, it wont work

[@suvarnadhavala0124]

@@AbhishekVeeramalla in ec2 instance i see the same error :( then what would work for windows could you please help me on this...

[@Kavya_9741]

Hi Abhishek, While practicing I just noticed to open a file in ready only mode we use -R . -r is used to recover a file from previous vim session. Can you please correct me if there is anything wrong?

[@KUSUMAV-fc8ug]

we can also use the "cat" command for read-only mode. isn't it?

[@AbhishekVeeramalla]

yes. we can

[@IJAZAhmed-ji7vj]

please make an video on networking commands.

[@lingrajbiradar4416]

please make video on deploying java application to kubernetes with sonar and nexus integration using CI CD Please

[@AbhishekVeeramalla]

Will try for sure

[@lingrajbiradar4416]

@@AbhishekVeeramalla thank you

[@VDenys]

7:13 -(I made a timeline for my own notes)

[@adewaleayeni-bepo2072]

I don't have the key for the OR symbol for the mathematical question. How do I write OR?

[@prakashbohara718]

nice video sir .. diff between tar gzip and zip ?

[@24_vishalmourya31]

I think the 2 you did was incorrect. The number should divide by both 3 and 5. I question it's AND not OR.

[@shashank7533]

what's the use of shebang /bin/bash why only use bin instead of etc or other files pls explain

[@tanyasinghal6945]

can anyone help me to get the output of the code at timestamp 18.24 as I have written same code but not getting anything?

[@ashokveerasamy9241]

one my interviewer ask me how do you clean apache webserver logs without deleting? can you clarify me bro..

[@AbhishekVeeramalla]

May be he is asking about log rotation ?

[@pavankumarsd9314]

Start adavance level Brother we are waiting

[@sarikagayakwad6727]

Please share the Linux system admin interview preparation procedure

[@Maayu25]

hello abhishek when i use gitbash find the number division with 3 and 5 the script is not execute it will give expr $i%3==0 command is not found can you share the trouble shoot

[@ravindraravi7435]

Thank you ^^

[@AbhishekVeeramalla]

You're welcome 😊

[@nagarjunam3584]

Question:- write a script to print only errors from a remote log i've a logs file which is located on other site.. wanna review logs using curl command curl is using to test the access the https address with html body the remote file how to access ? its via github? all remote files logs stores on github ?? how the curl can get the remote file access and do the log review ? kindly clear

[@AbhishekVeeramalla]

the same project is explained in future video in this series, please check the shells scripting playlist