补丁命令的"-Np1"选项有什么作用？

Question

有人给我发了一个补丁，告诉我使用命令:

patch -Np1 -i file.patch

出于好奇，我试图找出-Np1选项的作用，但补丁手册页对此奇怪地不透明。有人能解释一下这是怎么回事吗?谢谢。

Answer 1

这是两个标志。-N和-p1.

-N  or  --forward
Ignore patches that seem to be reversed  or  already  applied.   See
also -R.

和

-pnum  or  --strip=num
Strip the smallest prefix containing num leading slashes  from  each
file  name found in the patch file.  A sequence of one or more adja-
cent slashes is counted as a single slash.  This controls  how  file
names  found  in  the  patch file are treated, in case you keep your
files in a different directory than the  person  who  sent  out  the
patch.  For example, supposing the file name in the patch file was
/u/howard/src/blurfl/blurfl.c
setting -p0 gives the entire file name unmodified, -p1 gives
u/howard/src/blurfl/blurfl.c
without the leading slash, -p4 gives
blurfl/blurfl.c
and  not specifying -p at all just gives you blurfl.c.  Whatever you
end up with is looked for either in the current  directory,  or  the
directory specified by the -d option.