Grep 不匹配回车符

Question

我试图找到带有回车符的行，但我没有得到我期望的结果。我已经将其缩减为这个概念验证：

$ uname -a
CYGWIN_NT-6.1 Aodh 2.0.4(0.287/5/3) 2015-06-09 12:22 x86_64 Cygwin

$ grep --version
grep (GNU grep) 2.21
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and others, see <http://git.sv.gnu.org/cgit/grep.git/tree/AUTHORS>.

$ od -c cr_poc.txt
0000000   h   e   l   l   o       w   o   r   l   d   ;  \r  \n  \r  \n
0000020

$ od -x cr_poc.txt
0000000 6568 6c6c 206f 6f77 6c72 3b64 0a0d 0a0d
0000020

$ grep $'\r' cr_poc.txt; echo $?
1

我已经尝试了各种其他方法来为\r角色搜索，但都没有奏效。

请注意，这是在 Cygwin 上，这当然可能是问题的一部分。

Answer 1

浏览各种输入，我觉得grep行尾有自己的魔力：

$ printf "foo\rbar\n" | grep -oz $'\r' | od -c
0000000  \r  \n
0000002
$ printf "foo\rbar\r\n" | grep -oz $'\r' | od -c
0000000
$ printf "foo\rbar\r" | grep -oz $'\r' | od -c
0000000  \r  \n  \r  \n
0000004

（这-z是我试图grep匹配所有内容的蹩脚尝试。）所以我搜索了联机帮助页LF，导致我：

-U, --binary
      Treat the file(s) as binary.  By default, under MS-DOS  and  MS-
      Windows,  grep  guesses the file type by looking at the contents
      of the first 32KB read from the file.  If grep decides the  file
      is  a  text  file, it strips the CR characters from the original
      file contents (to make regular expressions with  ^  and  $  work
      correctly).  Specifying -U overrules this guesswork, causing all
      files to be read and passed to the matching mechanism  verbatim;
      if  the  file is a text file with CR/LF pairs at the end of each
      line, this will cause some regular expressions  to  fail.   This
      option  has  no  effect  on  platforms other than MS-DOS and MS-
      Windows.