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VI editor

Introduction to VI editor The term VI stands for visual editor. It was developed by Bill Joy in 1976 at the University of California at Berkeley. The term editor means program that is used to create and modify the contents of a file. A ‘VI’ editor is designed to deal with text files. It is a classic screen based editor rather than line editor that allows user to see some part of his file on terminal screen. It is a full screen editor and allow the user to view and modify character and lines by simply typing at the current cursor position. Operation Modes: It has two modes of operation such as: Command mode Insert mode Escape mode Command mode                                                                                      When ‘vi’ editor is started it is in command mode first. It enables you to perform administrative tasks such as saving or...

Directory and its command

Introduction to Directory A directory is a location where files such as ordinary, special, or directory are kept in a list. It stores file name and its related information. UNIX uses a hierarchical structure for organizing files and directories. This is known as a directory tree. It has a single root node which contains the slash character (/), and all other directories are contained below it. Listing files and directories LS command The ls command is used to display all files and directories in the current directory. To display all files in the current directory use ls command. By default it displays all files in alphabetical order except hidden files. But if current working directory is empty your command will get prompt immediately.            $ls             $ Here LS command is used with...

Filters and commands in UNIX

Introduction to filters A filter is a small and specialized program in UNIX that does some manipulation of the text of a file. It accepts input from the standard input processes the input and then send the output to standard output. Standard input is data source for a program, and by default it is text typed in at the keyboard. Therefore it can be directed to another file or another output in program. Standard output is the destination of output from a program, and by default it the display screen. It is used to extract the lines which contain a specific pattern and to arrange the content of a file in a sorted order or to replace the existing characters with other character and so on. It is used to store the intermediate result of a long pipe by using vertical bar (|) and merge two or more files together using filters. Various...