These format options provide fine-grained control over the output
of diff, generalizing -D/--ifdef.
LTYPE 可以是‘old'、‘new'或‘unchanged'。GTYPE 可以是 LTYPE 的选择
或是‘changed'。
GFMT (only) may contain:
%< lines from FILE1
%> lines from FILE2
%= lines common to FILE1 and FILE2
%[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER
LETTERs are as follows for new group, lower case for old group:
F first line number
L last line number
N number of lines = L-F+1
E F-1
M L+1
%(A=B?T:E) if A equals B then T else E
LFMT (only) may contain:
%L contents of line
%l contents of line, excluding any trailing newline
%[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number
Both GFMT and LFMT may contain:
%% %
%c'C' the single character C
%c'OOO' the character with octal code OOO
C the character C (other characters represent themselves)
-d, --minimal try hard to find a smaller set of changes
--horizon-lines=NUM keep NUM lines of the common prefix and suffix
--speed-large-files assume large files and many scattered small changes
--help display this help and exit
-v, --version output version information and exit
FILES 的格式可以是‘FILE1 FILE2'、‘DIR1 DIR2'、‘DIR FILE...'或
‘FILE... DIR'。
If --from-file or --to-file is given, there are no restrictions on FILE(s).
如果 FILE 是‘-'，则由标准输入读取内容。
如果输入相同，则退出状态为 0；1 表示输入不同；2 表示有错误产生。
