Sed Stream Editor Study Notes

Addresses and Line Selection

How to target specific lines in sed using line numbers, regex patterns, ranges, and the negation operator so commands run only where you want.

Append, Insert, and Change

The a, i, and c commands let sed add new lines after or before a matched line, or replace matched lines entirely, without relying on the substitute command.

Backreferences and Groups

Master capturing parts of a match with groups and reusing them via backreferences in both the pattern and the replacement of sed substitutions.

Branching and Loops in sed

Learn how sed uses labels, unconditional branches, and conditional branches to build loops and control flow inside its scripting language.

Building a Text-Processing Script

Move from ad-hoc one-liners to a maintainable multi-command sed script file, using labels, the hold space, and -f to solve a real data-cleaning task.

Common sed Idioms

A curated set of battle-tested sed one-liners for deletion, printing ranges, in-line insertion, and squeezing blank lines that you will reach for again and aga…

Config File Editing with sed

Using sed to safely automate edits to configuration files — in-place editing with backups, targeting keys precisely, and pitfalls when scripting changes to pro…

Grouping Commands with Braces

Using { } to bind multiple sed commands to a single address so they execute together as a block, including nesting and separator rules.

In-Place Editing

Learn how sed's -i option edits files directly on disk, how to create backups, and the portability differences between GNU and BSD/macOS sed.

Line Ranges and Steps

Selecting spans of lines in sed using numeric ranges, the $ last-line symbol, regex-bounded ranges, and GNU's first~step notation for periodic selection.

Multiline Processing

Learn how sed handles multiple lines at once using the pattern space, the hold space, and the D, P, N, H, and G commands to perform edits that span line bounda…

Negating Addresses

Using the ! operator to invert a sed address so a command runs on every line the address does NOT select, plus common idioms and gotchas.

Performance and Portability

How to write sed that runs fast on large files and behaves identically across GNU, BSD/macOS, and POSIX sed — covering common divergences and optimization tech…

Reading and Writing Files

The r, R, w, and W commands let sed pull the contents of external files into the output stream and write matched lines out to separate files during a single pa…

Regular Expressions in sed

How sed matches text using Basic and Extended Regular Expressions, including anchors, character classes, quantifiers, and the escaping rules that trip people u…

Running sed Scripts

How to invoke sed from the command line and from script files, including the key options that control input, output, and multi-command execution.

sed Best Practices

Practical habits for writing sed one-liners and scripts that are readable, portable, and safe to run against real data.

sed in Shell Pipelines

How to wire sed into Unix pipelines as a stream filter, combining it with cat, grep, sort, and xargs to build powerful one-liner text-processing workflows.

sed Interview Questions

The concepts interviewers probe most — the difference between sed and grep/awk, in-place editing, greedy matching, and multi-line handling — framed as question…

sed Quick Reference

A compact, scannable cheat sheet of sed's essential commands, addresses, flags, and regex constructs for fast day-to-day lookup.

sed Substitution Basics

A practical guide to the s command — sed's find-and-replace engine — covering delimiters, flags, backreferences, and the ampersand.

sed vs awk vs grep

A comparison of the three classic Unix text tools — when to reach for grep to search, sed to edit streams, and awk for field-oriented and programmable processi…

Substitute Command Flags

The flags that follow the sed substitute command control how many matches are replaced, whether matching is case-insensitive, and what happens after the replac…

Text Transformation Recipes

A practical cookbook of proven sed one-liners for everyday text surgery: deleting lines, extracting ranges, joining lines, and reformatting with capture groups.