Using sha256sum command for ensuring file integrity

sha256sum command generates and checks the SHA256 checksum for files. How to use sha256sum command for SHA256 is explained with an example.

File I/O in Linux

Buffered I/O and synchronized I/O and the input output system calls, open, creat, read, write, lseek, close and unlink are explained.

Files are used to store information on persistent secondary storage. FIles and processes are basic concepts in Unix-like systems.

A Perl script for generating the report of the most frequent visitors to a website from the nginx log file is given.

Git is a popular, widely used, source code management system, originally developed by Linus Torvalds. Common Git commands are listed.

bash idioms are tiny scripts, mostly one-liners, that accomplish a lot and can be used as building blocks in larger scripts.

comm compares two sorted files and gives three column output regarding, lines unique to file 1, lines unique to file 2 and the common lines.

grep is a program for searching string patterns in files. It searches files for the patterns and prints the matching lines.

Shell is the command line user interface to a UNIX-like system. bash is the default shell under Linux.

The umask command is used for setting a mask which is used for managing the permissions of files created by processes during a login session.