diff

文字處理

用法

diff -u [old] [new]

顯示兩個檔案之間改了什麼；patch 和程式碼審查期待的是 -u 統一格式，而有差異時結束碼是 1，會讓開了 set -e 的指令檔中斷。

常用選項

選項	含義
-u	Unified output, the format patch and code review expect
-r	Compare two directory trees
-q	Only say whether the files differ
-w	Ignore all whitespace
-i	Ignore case
-N	Treat a missing file as empty, which patches need

範例

diff -u old.conf new.conf > fix.patch

Writes a patch file.

diff -rq dirA dirB

Lists which files differ between two trees.

diff <(sort a.txt) <(sort b.txt)

Compares two files ignoring line order (bash).

它們本來就是用管線串起來用的。串三條往往比讓一條命令做完所有事更短。

怎麼看

Q. diff 是做什麼的？

顯示兩個檔案之間改了什麼；patch 和程式碼審查期待的是 -u 統一格式，而有差異時結束碼是 1，會讓開了 set -e 的指令檔中斷。

Q. 怎麼寫？

diff -u [old] [new] —— 方括號表示可以省略的部分。

Q. 值得記的選項有幾個？

這裡列了 6 個，完整列表在 man diff。這條命令屬於文字處理。