进行 diff 时复制的上下文输出格式和统一上下文输出格式有什么区别？

Question

进行比较时，复制上下文输出格式和统一上下文输出格式有什么区别？

diff -NBur dir1/ dir2/  
diff -NBcr dir1/ dir2/  

Answer 1

显然你误读了说明书。该-u旗帜是为了统一上下文，不是 Unicode，-c用于复制的上下文，而不是“上下文格式”：

-c -C NUM --context[=NUM] Output NUM (default 3) lines of copied context.

-u -U NUM --unified[=NUM] Output NUM (default 3) lines of unified context.

找出差异的最直接方法是尝试一下：

$ cat >1
line
diff 
more
^D
$ cat >2
line 
ffid
more
^D

$ diff -c 1 2
*** 1   2010-12-14 09:08:48.019797000 +0200
--- 2   2010-12-14 09:08:56.029797001 +0200
***************
*** 1,3 ****
  line
! diff
  more
--- 1,3 ----
  line
! ffid
  more

$ diff -u 1 2
--- 1   2010-12-14 09:08:48.019797000 +0200
+++ 2   2010-12-14 09:08:56.029797001 +0200
@@ -1,3 +1,3 @@
 line
-diff
+ffid
 more

你明白有什么区别吗？