文本差异对比工具

How diff works

A diff algorithm finds the longest common subsequence between two texts — the largest set of lines that appear in both, in the same order. Everything left over is either an addition or a deletion.

This matters because a naive line-by-line comparison produces noisy output. Change one line in the middle of a paragraph and a naive diff flags every subsequent line as changed. The LCS approach correctly identifies that only one line actually differs.

Reading the output

• Red lines (-) were removed from the original
• Green lines (+) were added in the new version
• Unmarked lines are identical and shown for context

Common uses

• Reviewing a revision before sending it
• Checking whether a config file changed
• Comparing a generated output against a template
• Spotting a subtle edit in a contract or changelog

Tip

For large files, diff on the command line gives you more control:

diff -u original.txt modified.txt

Add --color=always for readable output and -w to ignore whitespace-only changes.