Operating System Articles - Page 152 of 199

Screen or sometimes also known as GNU Screen, is a terminal multiplexer. What it means is that it allows you the privilege to start a screen session and then open any number of windows inside that session.It might also be interesting to note that a process that is running in Screen will continue to run even when their window is not visible anymore.Installing Linux ScreenIn order to install the screen package if it is not already present on your linux distribution, you can run any of the suitable commands shown below for your machine.For Ubuntu and Debiansudo apt update sudo ... Read More

While there are plenty of ways to find the extension of a particular file in Linux using different utility commands, if we need to find all the distinct file extensions in a folder hierarchy we need to first understand the uses of the find and the sed command as these commands will be used to print all the distinct file extensions in a folder or a folder hierarchy.The two Linux utility commands that we must be aware of are −find − used to locate a particular file or directorysed − short for stream editor and is used to perform functions ... Read More

There are many scenarios where we think that we have opened a file to make changes to it using the root user but when we actually try saving the changes, we realize that the file was opened with a normal user or with a user that doesn’t have the specific permission to edit the file. In such cases, we usually have only one option and that is to close the file with the command shown belowq!And then, open the file again with the command shown belowsudo su vi file.txtMake changes and save the file with the command shown belowwq!While this ... Read More

There are plenty of ways to generate a hash on any operating system, but when we talk about generating an almost-unique and fixed size bit hash, then nothing can replace the SHA algorithm.Before making use of the Linux command to generate a SHA-256 hash, we must know what SHA actually is and what it is good for.SHA-256 in very simple terms is a cryptographic hash function that has a digest length of 256 bits. It is an algorithm on its own that is able to generate an almostunique and fixed size 256-bit(32-byte) hash. It is also good to know that ... Read More

One thing that is constant about working with Linux is that we will make changes to one file or another with time. There are some files that stay unchanged, for example the files inside the /usr/local/ directory while there are some files that are just temporary and get deleted automatically, like the files or folders you insert in the /tmp directory.Since we know that change is imminent to files and folders, Linux also provides us with different ways to keep track of the files or folders that we change or have changed.The most common way to check if we have ... Read More

Let’s consider a case where we have two directories, say, d1 and d2 and both these directories contain some files, which may be the same or different. Now we want to list out the names of those files that are present in one of these directories say d1 and not present in the other directory say d2.In order to do that we must be familiar with either the diff command or the comm command, as both these commands can be used to solve the above problem.Let’s first explore the diff command, which is short for difference. This command is used ... Read More

Let’s say that we have two files inside a directory called dir1, and at first both these files are different. Different in the sense that the text they contain isn’t the same.The files in the folder −immukul@192 dir1 % ls -ltr total 16 -rw-r--r-- 1 immukul staff 7 Jul 7 10:37 2.txt -rw-r--r-- 1 immukul staff 8 Jul 8 19:05 3.txtThe contents inside the first file(2.txt) looks something like this −immukul@192 dir1 % cat 2.txt orangeThe contents inside the second file(2.txt) looks something like this −immukul@192 dir1 % cat 3.txt uorangeWe can easily make use of the diff command to ... Read More

In order to understand the syntax of a crontab job, we first need to explore and understand what a crontab job is.A crontab is nothing but a list of commands that we can run during a cron job. A cron job is a utility that schedules automatic execution of commands at specific times.We can start a cron job with the help of bash script by following the commands shown below −crontab -eThis will open a file which you can edit, insert the cron job shell script in the above file and then close that file.Just insert the code shown below ... Read More

XLSX file is a standard file extension for the modern Microsoft Excel spreadsheet. We use of these files to analyze and organize data and they usually contain numerical data separated by rows and columns within a cell.On the other hand, a CSV file is basically a delimited text file that uses a comma to separate values, and each line of this file is usually a data record.While both the xlsx and csv formats of storing data are way different, as one makes use of tables with rows and columns, while the other uses commas to separate the values, but that ... Read More

We know that most of the time we want our node applications to listen on port 80. While it is a widely used technique and many times we don’t need anything else then just simply mentioning the port as 80 in our project configurations. The real issue actually resides in the fact that many of the operating systems nowadays require root privileges for this to happen (e.g., OS X, BSD).One workaround is to make sure that we start our application with the superuser.Commandsudo node server.jsWhile this might actually solve the problem for quite an extent, this approach has its vulnerabilities ... Read More