Using sha256sum command for ensuring file integrity
1.0 SHA-2 A cryptographic hash function (CHF) is an algorithm to map arbitrary size data, called the message, to a fixed sized bit array, called the hash value, or message…
File I/O in Linux
1.0 Input and Output (I/O) All programs need to interact with the external world which makes I/O important. Programs store data in files which provide large persistent storage. In this…
Files in Linux
1.0 Files There are two basic concepts in Linux - processes and files. The processes do things and files keep all the important data. An efficient filesystem is important for…
Analyzing the NGINX web server log file
1.0 Introduction Given an nginx web server log file, we might like to know who are the visitors to our website. One can go line by line through the log…
Using Git
1.0 Introduction Git commands for common source code management use cases are listed. 2.0 Install Git On an Ubuntu Linux system, Git can be installed with the command, $ sudo…
Bash idioms
bash idioms are tiny scripts, mostly one-liners, that accomplish a lot and can be used as building blocks in bigger scripts. 1.0 Find most frequent words Suppose we have a…
comm command in Linux
1.0 comm The comm command compares two sorted files and gives output in three columns. The first column has lines which are present only in the first file. The second…
grep Command in Linux
1.0 grep grep is a program for searching a given string pattern in files. It searches the files for the pattern and prints the lines that contain strings matching the…
An Introduction to Shell in Linux
1.0 SHELL A shell provides a user interface to a computer system. There are two types of shells, the command line interface (CLI) and the graphical user interface (GUI). In…
umask in Linux
File Permissions In Linux, each files has nine permission bits. There are three basic permissions, read (r), write (w) and execute (x), for a file. These three permissions are there…