Operating System Articles - Page 132 of 179

In normal cases we make use of the bash_profile or bashrc in case of Ubuntu and zshrc in case of Mac OS, to set our environment variables and then those variables are made available to us everywhere on the terminal we want.Let’s consider a simple example where we have some environment variable in bash_profile and we are making use of it in the terminal.Consider the bash_profile output shown below −immukul@192 dir1 % cat ~/.bash_profile export JAVA_HOME=$(/usr/libexec/java_home) export PATH=$PATH:/usr/local/node/bin export GOROOT=/usr/local/go export GOPATH=/Users/immukul/go_projectsAs we can see there are many variables present in the bash_profile file, we can use these variables in ... Read More

Linux provides us with different utility commands that we can make use of to print a random line from any files in the Unix command line. Mostly we make use of either the shuf command or the sort command, and in this article I’ll explain both the commands and which one is better and why.Shuf CommandThe shuf command in Linux is used to write random permutations of the input lines to the standard output. The idea of randomizing the input is the same as one does when the cards are shuffled. On most of the Linux operating systems it is ... Read More

Linux provides the famous top command utility that provides us with all the information about the processes, their time, their respective IDs, how much CPU chunk they are consuming and much more. The only issue with that is the processes are not sorted in any order and the order changes frequently.There are certain cases where we would like the output to be in a sorted manner somehow, like sorted in the sense that the process which is using the most network will be at the top.One such command line program that we can use that will provide us the desired ... Read More

We know that an operating system is considered the backbone of any system that you may use. The three most common and widely used operating systems share things in common just as well as they share differences. While there are cases where one might outperform another, those cases and such scenarios are very rare.The most notable difference one can notice is how they store the files in their file structure, like in case of windows, it follows a directory structure to store the different kinds of files of the user, whereas the Mac OS file structure is known as MAC ... Read More

We know that the SED command in Linux stands for stream editor and is mainly used to perform functions on files, and the functions usually are either searching for a word, or replacing it or insertion of something and few more. It is a very useful command and can be found on the Linux kernel.It should also be noted that the BSD (Berkeley Software Distribution) sed shipped with the OS X does need the -i flag to work and the GNU one doesn’t.One way to make the GNU version of the SED to work on the Mac OS X, is ... Read More

We know that the Pause command in DOS is used to suspend execution of the batch files and it then displays the messageStrike a key when ready ...It should also be noted that some versions of DOS also allow a comment to be entered on the same line as PAUSE.ExampleWe can make use of the Pause command in a scenario where we want to suspend the execution of a batch file and display the message “Insert Code”, by typing the following command in the terminalpause Insert CodeSo, that was all about the Pause command in DOS, but we want to ... Read More

The key difference between the fopen() and the open() function in the Linux operating system is that the open() function is a low-level call, where the fopen() when called simply calls the open() function in the background and it returns a Filepointer directly.The call to the open() function includes invoking several other functions and the behaviour of the entire process is mentioned below as a reference to understand the open() function better.Consider the code shown below −int sys_open(const char *filename, int flags, int mode) {    char *tmp = getname(filename);    int fd = get_unused_fd();    struct file *f = ... Read More

When we are talking about opening a file, then we have different cases such as in what language and what API are we actually calling when opening a file. While in most of the cases it is quite simple, the higher level languages will eventually call either the C API or directly invoke the Linux open() function which is also written in C.If we try to talk about different languages then this is a very broad question and cannot be covered in a one single article, and that is because of the sheer complexity that gets added to it when ... Read More

There is a decent chance that if you have used Linux operating systems then you might have encountered the three famous data streams known as stdin, stderr and stdout. All these are different in their functions and have their own uses but one thing common between all three of them is that they are data streams that bash creates.Let’s understand more about what data streams actually mean and how they are beneficial. In terms of computing, a data stream is something that gives us the ability to transfer data from a source to an outflow and vice versa. The source ... Read More

In order to understand what the libraries of files with the extensions .a, .so and .la actually mean, we first must be aware of the concept of libraries in Linux. A Linux in its very simple terms is a collection of pre-compiled pieces of code which are known as functions. Libraries are very useful as they provide reusable functions, classes and data structures. Some examples of libraries in Linux are glibc (GNU version of standard C library), libc (the C standard library).In total we can divide the libraries in Linux in two categories. These categories are −Static LibrariesDynamic LibrariesStatic LibrariesThe ... Read More