In Ubuntu Older versions, the SageMath notebook could be opened by typing “sage notebook()” in the terminal, but In the latest version of Ubuntu (say, 21.04), SageMath is using “Jupiter Notebook” instead of Notebook.

In order to open Jupyter Notebook in SageMath, you have to open the terminal (Alt+Ctrl+T) and write jupyter notebook then press enter.

# Eleven scientists are working on a secret project. They wish to lock up the documents in a cabinet so that the cabinet can be opened if and only if six or more of the scientists are present. What is the smallest number of locks needed? What is the smallest number of keys to the locks each scientist must carry?”

If we put for each combination of 6 scientists a lock, then that’s (choose 6 from 11)=462 locks. Now so that the locks can be opened if 6 scientists are there, every scientist needs at least the keys for every combination of scientists that includes him. Thats’s (choose 5 from 10)=252 keys. To assure that the locks can’t be opened if less scientists are there, we give them no more than the 252 keys that they need.

# How to mirror PDF file text easily via command line?

We can easily mirror the contents of a PDF file. When printing in booklet format in the press, you have to mirror the PDF page while printing. We can do the mirroring using the following command line

# Mirror in the vertical axis:

convert -flip inputFile.pdf outputFile.pdf

# Mirror in the horizontal axis:

convert -flop inputFile.pdf outputFile.pdf

# CSIR-NET Mathematical Sciences Ten Years Question Papers || Full PDF Download

## CSIR NET  Math Question Papers

CSIR UGC NET Previous Math Question Papers with Answer Keys

## Joint CSIR-UGC NET exam

The CSIR is the Council of Scientific and Industrial Research conducting the Joint CSIR-UGC NET exam twice a year.  Now currently, National Testing Agency( NTA) conducts CSIR NET Exam twice a year in June and December. The CSIR NET exam is to be held for determining the eligibility of the candidates for the award of JRF (Junior Research Fellowships) NET and also for providing eligibility for the appointment of Lecturers (NET) in certain subject areas such as Chemical Sciences, Earth Sciences, Life Sciences, Mathematical Sciences, and Physical Sciences.

### Joint CSIR UGC NET exam pattern

The Joint CSIR-UGC NET exam pattern for the Single Paper MCQ (Multiple Choice Question)test contains:- The maximum marks for the exam is 200. The time duration of the exam is 3 hours.  Three parts are there in the question paper.

Part ‘A’ is common to all subjects. This part A may contain a maximum of 20 questions of General Aptitude. The candidates are requested to answer any 15 questions from the 20 questions. Two marks are to be awarded for each question. The total marks for Part ‘A’ are 30 (out of 200).

Part ‘B’ may contain subject-related MCQs. The total marks to be allocated to this part will be 70 (out of 200). The candidates are requested to answer any 35 questions from the 40 questions. Two marks will be for each question.

Part ‘C‘ may contain deep questions to test the candidate’s knowledge of scientific concepts and/or application of the scientific concepts. The candidates are requested to answer any 25 questions from the 60 questions. The total marks to be allocated to this part will be 100 (out of 200). Four marks are to be awarded for each question.

*  Negative mark will be 25% for each wrong answer.

1. Telegram Group: https://t.me/bettersolution4u
2. WhatsApp Group: https://chat.whatsapp.com/JOHmLrwUJePFMi1M4ISZBg
5. Website: https://bettersolution4u.blogspot.com

## Joint CSIR-UGC NET exam

The CSIR is the Council of Scientific and Industrial Research conducting the Joint CSIR-UGC NET exam twice a year.  Now currently, National Testing Agency( NTA) conducts CSIR NET Exam twice a year in June and December. The CSIR NET exam is to be held for determining the eligibility of the candidates for the award of JRF (Junior Research Fellowships) NET and also for providing eligibility for the appointment of Lecturers (NET) in certain subject areas such as Chemical Sciences, Earth Sciences, Life Sciences, Mathematical Sciences, and Physical Sciences.

### Joint CSIR UGC NET exam pattern

The Joint CSIR-UGC NET exam pattern for the Single Paper MCQ (Multiple Choice Question)test contains:- The maximum marks for the exam is 200. The time duration of the exam is 3 hours.  Three parts are there in the question paper.

Part ‘A’ is common to all subjects. This part A may contain a maximum of 20 questions of General Aptitude. The candidates are requested to answer any 15 questions from the 20 questions. Two marks are to be awarded for each question. The total marks for Part ‘A’ are 30 (out of 200).

Part ‘B’ may contain subject-related MCQs. The total marks to be allocated to this part will be 70 (out of 200). The candidates are requested to answer any 35 questions from the 40 questions. Two marks will be for each question.

Part ‘C‘ may contain deep questions to test the candidate’s knowledge of scientific concepts and/or application of the scientific concepts. The candidates are requested to answer any 25 questions from the 60 questions. The total marks to be allocated to this part will be 100 (out of 200). Four marks are to be awarded for each question.

*  Negative mark will be 25% for each wrong answer.

# Encrypt PDF with pdf in Linux or MacOS

QPDF is SUPER excellent PDF command line utality for Linux !!! It is SUPER excellent tool, being very powerful, able to perform highly difficult & specific operations on PDF files ……. .QPDF is a program that can be used to linearize (web-optimize), encrypt (password-protect), decrypt, and inspect PDF files from the command-line.

Install qpdf by entering the following commands in the terminal:

sudo apt update
sudo apt install qpdf

General syntax to encrypt pdf

To encrypt PDF file:
qpdf --encrypt user-password owner-password key-length [restrictions] -- inputfile.pdf outputfile.pdf

The User password, or sometimes called the “open” password is used to open a PDF file if a password is set. The other password, the Owner passwordis used to set what users can do with the PDF. It controls things like if a user is allowed to print, copy or modify a PDF. Either or both of the user password and the owner password may be empty strings. The value for key-length may be 40, 128, or 256. When no additional restrictions are given, the default is to be fully permissive.

Example:

qpdf --linearize --encrypt "bettersolution4u" "MKS" 128 --print=full --modify=none --extract=n --use-aes=y -- inputfile.pdf outputfile.pdf

# How to Add Header and Footer on Included PDF in LaTeX?

Using your current settings, the pdfpages inserts the pages of an external PDF file as full page additions to your existing document. That is, the external file page setup is copied to the “main” output PDF on a page-by-page basis. The “main” file’s page setup (including header/footer) is ignored.

If you wish to include the same header/footer style of your main document for each of the \includepdf pages, then you need to specify this using the pagecommand key-value.

Example:

\documentclass[headheight=1.2cm,headsepline,twoside]{scrartcl}
\usepackage[left=0.5in, right=0.5in,top=1in, bottom=2.8cm,footskip=18mm]{geometry}

\usepackage{hyperref}
\hypersetup{
linktoc=all,     %set to all if you want both sections and subsections linked
}

\usepackage{tabularx}
\usepackage{lipsum}
\usepackage{pdfpages}
\usepackage[english]{babel}

\cfoot[]{Center footer -- \thepage{} --}
\ifoot[]{Inside footer}
\ofoot[]{Outside footer}

% Easy interface
%\deftripstyle{pdfincl}
%  {}
%  {}
%  {Another inside footer}
%  {}
%  {Another outside footer}

% Expert interface
\newpagestyle{pdfincl}
(0pt,0pt)% no above rule
}
}
}
(0pt,0pt)% no above rule
}
{% FOOTER
(0pt,0pt)% no separation rule
{% footer, even pages
Another outside footer\hfil Another inside footer
}
{% footer, odd pages
\begin{tabularx}{\textwidth}{|l|>{\centering\arraybackslash} X|r|}\hline
Another inside footer &  Another outside footer & \hfill Page no.\thepage \\ \hline
\end{tabularx}%
}
{% footer, single side
Another inside footer\hfil Another outside footer
}
(0pt,0pt)% no rule below footer
}

\begin{document}

\title{Title of the Your Contents Here}
\author{Md Kutubuddin Sardar}
\date{\today}

\maketitle
\tableofcontents
%\section{Section Name}
%\section{Blah}
%\lipsum[3-5]

turn=false,scale=0.9,pages=-,
pagecommand={\thispagestyle{pdfincl}}]{preposition}
%\includepdf[addtotoc={1, subsection, 1, Included PDF,tag}, turn=false,frame,scale=0.9,pages=-,pagecommand={\thispagestyle{pdfincl}}]{preposition}
%\section{Section Name}
%\lipsum[3-5]
\end{document}

# How to Remove Files with Different Specific Extensions in Linux?

We use the ‘rm‘ (Remove) command to remove files with a specified extensions in Linux. It is a fundamental command-line utility for removing system files, directories, symbolic links, device nodes, pipes, and sockets in Linux. The command is straightforward to use and has the following syntax:

rm <filename1> <filename2> ... <filenameN>

Here, ‘filename1‘, ‘filename2‘, etc. are the names of the files including full path. If the files are in the same directory then, as you might already know, there is no need to write down full paths.

Suppose the temporary file such as file.aux, file.log, file.out are generated for compiling latex file. We can delete these easily as below:

rm -r *.out *.log *.aux

# Replace whitespace of a file name with underscore using Python

If you need to replace all the whitespace of all filenames in a directory with underscore ( _ ), then the following codes are the solution for you.

import re
import os
import glob

for filename in glob.glob('*.pdf'): #calling filename from directory by its extension
name, ext = os.path.splitext(filename) # separate file name and its extension
name = name.replace(" ", "_") # replace any whitespace by underscore
os.rename(filename,str(name)+'.pdf') # os.rename(OldName,NewName)


# How to Extract filename and extension in Bash?

If you want to get the filename (without extension) and the extension separately, see the code below.

First, get file name without the path:

#!/bin/bash

#get the  file in a directory

filename=ls *.pdf
#print file name
echo $filename extension="${filename##*.}"
echo $extension filename="${filename%.*}"
echo \$filename