Chapter 5. Redirection, Pipe and Shell Script
In this chapter, we’ll explore key Linux commands, including redirection of standard input, output, and error, the pipe to combine commands, and writing shell scripts to automate tasks. These commands form the core of Linux command-line operations, helping you to manage data input, output, and script executions effectively.
What We Cover in This Chapter
The following topics are covered in this chapter:
Standard Input Output and Redirection
In this section, we’ll explain the concept of standard input, output, and redirection. We’ll look at how these elements are managed in the Linux environment and explore how they work with commands like sort and cat for input and output redirection.
Pipe (Combine Commands)
In this section, we’ll show you how to use the pipe symbol (|) to link multiple commands together. This allows you to feed the output of one command as the input of another, making complex tasks simpler and faster.
less (Display Content with Pager)
In this section, we’ll explore the less command, a useful pager for viewing large files one page at a time. We’ll also demonstrate its use in combination with other commands like ls to paginate the output.
tr (Replace Characters)
In this section, we’ll dive into the tr command, which is used for translating or replacing characters. We’ll show you how to use it with pipes and file redirection to replace characters in a text stream.
cut (Extract Data Sections)
In this section, we’ll demonstrate the cut command, which extracts specific fields from a text file. We’ll explain how to use it to process delimited data and save the extracted information into another file.
uniq (Extract Unique Data Lines)
This section covers the uniq command, which filters out repeated lines in a file. We’ll also explore its usage with the sort command to extract unique data entries efficiently.
Shell Script
In this section, we’ll introduce you to shell scripting, which allows you to combine multiple Linux commands into a single script for automation. You’ll learn how to write simple scripts, make them executable, and run them from the command line.
echo (Echo Input)
This section will teach you the basics of the echo command, which outputs text or variable contents to the screen. You’ll learn how to use it with both strings and variables in a shell script.
read (Read and Store Input)
Here, we’ll cover the read command, which allows you to take user input from the command line and store it in a variable for later use.
Shell Variable and Environmental Variable
In this section, we’ll differentiate between shell variables and environmental variables. We’ll explain their scope and how environmental variables can be shared between processes.
source (Execute Shell Script and Refresh Environmental Variables)
This section will show you how to use the source command to execute shell scripts and refresh environmental variables without leaving the current shell session.
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