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Linux Command Line Mastery · 课时

使用 `sed` 和 `awk` 操作文本

使用 `sed` 进行流编辑，使用 `awk` 进行高级文本处理和报告生成。

使用 `sed` 和 `awk` 操作文本 是 CoddyKit 上的免费 Linux Command Line Mastery 课时。 这是第 3 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Linux Command Line Mastery 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Linux Command Line Mastery 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Meet `sed` and `awk`

Welcome to a powerful lesson on text manipulation! We'll explore two essential Linux command-line tools: sed and awk.

These tools are incredibly useful for editing and processing text files, making them indispensable for system administrators, developers, and data analysts.

  • sed (Stream Editor): Great for simple text transformations like finding and replacing text or deleting lines.
  • awk (Pattern Scanning and Processing Language): A more robust language for advanced data extraction, reporting, and conditional processing.

`sed` for Simple Substitutions

The most common use for sed is substitution. You can replace specific text patterns on a line using the s command, which stands for substitute.

The basic syntax is sed 's/pattern/replacement/'. By default, it replaces only the first occurrence of the pattern on each line.

echo "hello world, hello universe" | sed 's/hello/hi/'

Global & Case-Insensitive `sed`

What if you want to replace all occurrences on a line, or ignore case? sed has flags for that!

  • The g flag (global) replaces all matches on a line.
  • The i flag (case-insensitive) makes the pattern matching ignore uppercase/lowercase differences.

You can combine flags, like gi.

echo "Apple apple APPLE" | sed 's/apple/orange/gi'

Deleting Lines with `sed`

Beyond substitution, sed can also delete entire lines based on a pattern or line number. The d command is used for deletion.

To delete lines containing a specific word, you'd use sed '/pattern/d'. You can also delete specific line numbers, like sed '2d' for the second line.

echo -e "Line 1
REMOVE THIS LINE
Line 3" | sed '/REMOVE/d'

Inserting & Appending Lines

sed can also insert new lines of text before or after existing lines. This is useful for adding headers, footers, or context to your files.

  • The i command inserts text before a matched line.
  • The a command appends text after a matched line.

The text to insert/append must be on a new line after the command, or escaped with a backslash.

echo "Existing line" | sed 'i\New line before'

`awk` for Pattern Scanning

Now, let's dive into awk. It's more than just a stream editor; it's a programming language designed for pattern scanning and processing!

awk processes text files line by line. For each line, it checks if it matches a given pattern. If it does, it performs an associated action. The basic structure is awk 'pattern { action }'.

echo -e "apple
banana
orange" | awk '{ print }'

Working with `awk` Fields

A key feature of awk is its ability to automatically split each line into fields (columns). By default, whitespace (spaces, tabs) acts as the field separator.

  • $1, $2, $3, ...: Refer to the first, second, third field, and so on.
  • $0: Refers to the entire line.
  • -F option: Use this to specify a custom field separator, e.g., -F',' for comma-separated values.
echo "Name:Alice,Age:30" | awk -F',' '{ print "Hello, " $1 }'

Conditional Logic in `awk`

awk allows you to use conditional statements, like if, within its actions. This means you can process lines or fields only if certain criteria are met.

This is extremely powerful for filtering data based on numeric comparisons, string matches, and more.

echo -e "itemA 10
itemB 5
itemC 12" | awk '{ if ($2 > 8) print $1 " is expensive" }'

`awk`'s Handy Variables

awk provides several built-in variables that offer useful information during processing:

  • NR (Number of Record): The current line number being processed.
  • NF (Number of Fields): The total number of fields in the current line.
  • FILENAME: The name of the current input file.

These variables help you create dynamic and context-aware scripts.

echo -e "one two
three four five" | awk '{ print "Line " NR ": " NF " fields" }'

`sed` Substitution Quiz

Time to test your knowledge of sed!

`sed` & `awk` Recap

Great job! You've learned the basics of two incredibly powerful text processing tools: sed and awk.

  • sed is your go-to for stream editing, perfect for quick substitutions (s), deleting lines (d), and inserting/appending text. Remember the g (global) and i (case-insensitive) flags!
  • awk is a versatile language for pattern scanning. It excels at splitting lines into fields ($1, $2, ...), using custom delimiters (-F), applying conditional logic (if), and leveraging built-in variables like NR and NF.

Practice these commands to master your text manipulation skills!

常见问题解答

「使用 `sed` 和 `awk` 操作文本」课时是免费的吗？

是的 — 「使用 `sed` 和 `awk` 操作文本」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Linux Command Line Mastery 课程的其余内容，请升级到 CoddyKit PRO。 Linux Command Line Mastery 课程共包含 4 节课。

「使用 `sed` 和 `awk` 操作文本」这节课中我会学到什么？

使用 `sed` 进行流编辑，使用 `awk` 进行高级文本处理和报告生成。 你通过在浏览器中直接运行的动手代码来练习 Linux Command Line Mastery，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Linux Command Line Mastery 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Linux Command Line Mastery 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 3 节课，共 4 节。

「使用 `sed` 和 `awk` 操作文本」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Linux Command Line Mastery 课中编写并运行代码吗？

能。每节 Linux Command Line Mastery 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 标准流与重定向
  2. 使用 `grep` 过滤文本
  3. 使用 `sed` 和 `awk` 操作文本
  4. 使用 sort、uniq 和 cut 合并并排序输出
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