Book Image

Linux Shell Scripting Essentials

Book Image

Linux Shell Scripting Essentials

Overview of this book

Shell scripting is a quick method to prototype complex applications or problems. Shell scripts are a collection of commands to automate tasks, usually those for which the user has a repeated need, when working on Linux-based systems. Using simple commands or a combination of them in a shell can solve complex problems easily. This book starts with the basics, including essential commands that can be executed on Linux systems to perform tasks within a few nanoseconds. You’ll learn to use outputs from commands and transform them to show the data you require. Discover how to write shell scripts easily, execute script files, debug, and handle errors. Next, you’ll explore environment variables in shell programming and learn how to customize them and add a new environment. Finally, the book walks you through processes and how these interact with your shell scripts, along with how to use scripts to automate tasks and how to embed other languages and execute them.
Table of Contents (10 chapters)
9
Index

Knowing your history


Shells provide an interesting feature that allows you to find out the history of all commands you have executed previously in a shell. It often happens that we forget what command was typed on the previous day to perform a task. We may or may not be able to recall the exact syntax, but it is very convenient that we can refer to the history saved by the shell.

Shell variables controlling the history

There are shell variables that can be altered to change what and how much history a user can see. These shell variables are mentioned in the following table:

Name

Value

HISTFILE

Name of file in which by default history will be saved

HISTFILESIZE

Number of commands to be kept in history file

HISTSIZE

Number of history to be stored in memory for current session

HISTCONTROL

A colon-separated list of values controlling how commands are saved on the history list

The value of the HISTCONTROL shell variable can be:

Value

Description

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