sed

sed, short for "stream editor," is a powerful text-processing utility in Unix and Unix-like operating systems, including Linux and macOS. It's used primarily for parsing and transforming text data, such as extracting, replacing, and modifying strings or file content.

sed is non-interactive, meaning it processes text without requiring user intervention, making it well-suited for scripting and batch processing.

sed reads input line by line, processes it according to provided commands, and outputs the result. It's particularly efficient for handling large text files. It uses regular expressions for pattern matching, which allows for complex text manipulations.

It is capable of editing files in-place (with the -i option), modifying the original file with the changes. It is commonly used for its search and replace functionality, which allows for the substitution of text patterns. sed commands can be scripted, enabling complex text transformations in shell scripts.

Some common uses for sed include:

• Text Replacement: Replacing words or patterns in a file. For example, to replace "cat" with "dog" in a file:

sed 's/cat/dog/' filename.txt

• Data Extraction and Reporting: Extracting specific data from text files, such as logs or configuration files.
• File Formatting and Text Conversions: Modifying the format of text data, like converting dates or removing whitespace.
• Automating Text Edits in Scripts: Using within shell scripts or in combination with other Unix tools for batch processing.

A simple example of Sed may be:

sed 's/foo/bar/g' input.txt > output.txt

This command replaces every occurrence of "foo" with "bar" in input.txt and writes the result to output.txt. The s stands for substitute, and the g at the end signifies a global replacement (replace all occurrences, not just the first one).