Errno is a value that you get when the command you run returns the value of the call indicating an error. There is a header file that defines the integer variable errno, which is set by the system calls and some library function in the event of an error to let the developer know what’s wrong.In simple terms, the “errnos” are symptoms of operating system errors. Generally produced by failed operating system calls.In UNIX, the errnos are defined in upper case letters.ExampleEPERM ENOENT ESRCH EINTR EIO ENXIOIn the above examples, some formatted errnos are mentioned that have different values and ... Read More

In order to iterate over a list of files we will need to make use of the find command that Linux provides us with.Linux find statement is one of the most widely used statements that allows us to walk a file hierarchy. It is used to mostly find a specific file or directories and we can also append different other Linux statements or flags along with it to enhance or do a complex operation.Let’s explore an example of a find statement to understand it better.In the Linux code shown below, I am trying to search for a file inside my ... Read More

In order to be able to invert a grep expression on Linux command line, we must first understand what a grep command is and how to use it on Linux.The grep command in Linux is used to filter searches in a file for a particular pattern of characters. It is one of the most used Linux utility commands to display the lines that contain the pattern that we are trying to search.Normally, the pattern that we are trying to search in the file is referred to as the regular expression.Syntaxgrep [options] pattern [files]While there are plenty of different options available ... Read More

Installing the latest version of Git on CentOS can be done in many ways. Below are three approaches for the same.Approach 1Commandsyum install epel-release yum remove git rpm -U https://centos7.iuscommunity.org/ius-release.rpm yum install git2u git --versionOutputimmukul@192 lib % git --version git version 2.29.2Approach 2Commandsyum install -y curl-devel expat-devel gettext-devel openssl-devel zlib-devel gcc perl-ExtUtils-MakeMaker export GIT_VERSION=2.29.2 mkdir /root/git cd /root/git wget "https://www.kernel.org/pub/software/scm/git/git-2.29.2.tar.gz" tar xvzf "git-2.29.2.tar.gz" cd git-2.29.2 make prefix=/usr/local all make prefix=/usr/local install yum remove -y git git --versionOutputimmukul@192 git-2.29.2 % git --version git version 2.29.2Approach 3Commandssudo yum -y install https://packages.endpoint.com/rhel/7/os/x86_64/endpoint-repo-1.7-1.x86_64.rpm sudo yum install git git --versionOutputimmukul@192 git-2.29.2 % ... Read More

In order to insert text at the beginning of a text file we must be familiar with either the sed command as the sed commands can be used to solve the above problem.Let’s first explore the sed command, which is short for stream editor. This command is used to perform different functions like find, replace, insert and many more on a particular file.Consider we have a directory d1 in which two .txt files are present and the directory looks something like this −immukul@192 d1 % ls -ltr total 8280 -rwxrwxrwx 1 immukul staff 4234901 Jul 7 17:41 ... Read More

We know that we can make use of the grep command to search for a particular pattern of characters in all the lines of a file or multiple files. The grep command performs a case-insensitive search for words in a file.Let’s see a simple example where we will grep a pattern in all the files that are present in a directory.Commandgrep -i ‘lp’ Sample*OutputSample: The sample was printed via the internet. Sample: I believe lp cares about what the device is. Sample1: This was printed via the internet. Sample1: I believe lp cares about what the device is. Sample2: This ... Read More

In order to be able to grep multiple lines of pattern present in a file, we will make use of the number of grep command that Linux provides us with. But first, we must understand what a grep command is and how to use it on Linux.The grep command in Linux is used to filter searches in a file for a particular pattern of characters. It is one of the most used Linux utility commands to display the lines that contain the pattern that we are trying to search.Normally, the pattern that we are trying to search in the file ... Read More

While there are plenty of ways to print and make use of specific words from a particular file in a Linux directory, when we talk about grepping a particular word and then replacing it with some other word, then we will need to mix certain Linux utility commands.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 like searching, editing and replacing.In order to solve the problem of grep and replace a particular word we will make use ... Read More

The grep command in Linux is used to filter searches in a file for a particular pattern of characters. It is one of the most used Linux utility commands to display the lines that contain the pattern that we are trying to search.Normally, the pattern that we are trying to search in the file is referred to as the regular expression.Syntaxgrep [options] pattern [files]While there are plenty of different options available to us, some of the most used are −-c : It lists only a count of the lines that match a pattern -h : displays the matched lines only. ... Read More

Whenever we want to get an update about a specific process or different process we make use of the ps command which is short for “Process status” that tells us about the state of the current process and its characteristics and a whole lot more.When clubbed with several flags and commands we can enhance the ps command to output the start time of different processes that are running on a particular Linux machine.The command to print the time of long running processes in increasing order is shown below −For Ubuntu and other Linux based Systems −ps -eo pid , lstart ... Read More