Core Utilities and the Unix Data Model

4. Core Utilities and the Unix Data Model#

This chapter focuses on the Unix idea that text streams, files, and small composable utilities can solve large practical problems.

Streams: Follow data through standard input, output, and error.
Inspection: Choose commands that reveal enough of a file without overwhelming the terminal.
Filtering: Search and select text with patterns and regular expressions.
Transformation: Reshape text with tools such as sort, uniq, cut, sed, and awk.
Pipelines: Combine commands so each tool performs one clear step.

Chapter Video

How to Use Redirection and Pipelines in Bash (9:50) by Microsoft Developer

Hosted on YouTube; property of its original creator, embedded here for educational reference only.

Learning Objectives

By the end of this chapter, you will be able to:

Explain how the Unix data model treats files and streams.
Inspect text and binary data with standard command-line tools.
Combine commands with pipes and redirection.

Chapter Flow

Glossary

#	Term	Explanation
1	Standard input	The default input stream read by a command.
2	Standard output	The default stream where a command writes normal output.
3	Standard error	The stream where a command writes diagnostics and errors.
4	Text stream	A sequence of text data flowing into or out of a process.
5	Pipeline	A chain of commands connected so output from one becomes input to the next.
6	Pipe	The `
7	Redirection	Shell syntax that sends input or output to files or other streams.
8	`cat`	A command that writes file contents to standard output.
9	`less`	A pager for reading text interactively.
10	`head`	A command that shows the beginning of a file or stream.
11	`tail`	A command that shows the end of a file or stream.
12	`file`	A command that reports the likely type of a file.
13	`wc`	A command that counts lines, words, and bytes.
14	`grep`	A command that searches text for matching lines.
15	Regular expression	A pattern language for matching text.
16	`find`	A command that searches directory trees for matching files.
17	`sort`	A command that orders lines of text.
18	`uniq`	A command that collapses or counts adjacent duplicate lines.
19	`sed`	A stream editor commonly used for substitutions and line filtering.
20	`awk`	A pattern-action language for field-oriented text processing.