string - 空格/制表符/换行不敏感比较

Question

假设我有这两个文件:

文件 1:1 2 3 4 5 6 7

文件 2:

1
2
3
4
5
6
7

是否可以使用diff 来比较这两个文件，使结果相等？

(如果不能，我应该使用哪些其他工具？)

谢谢

Answer 1

您可以折叠空格，使 file2 看起来像 file1，每个数字都在同一行:

$ cat file1
1 2 3 4 5 6 7
$ cat file2
1
2
4
3
5
6
7
$ diff <(echo $(< file1)) <(echo $(< file2))
1c1
< 1 2 3 4 5 6 7
---
> 1 2 4 3 5 6 7

解释:

< file             # Equivalent to "cat file", but slightly faster since the shell doesn't
                   #     have to fork a new process.

$(< file)          # Capture the output of the "< file" command. Can also be written
                   #     with backticks, as in `< file`.

echo $(< file)     # Echo each word from the file. This will have the side effect of
                   #     collapsing all of the whitespace.

<(echo $(< file))  # An advanced way of piping the output of one command to another.
                   #     The shell opens an unused file descriptor (say fd 42) and pipes
                   #     the echo command to it. Then it passes the filename /dev/fd/42 to
                   #     diff. The result is that you can pipe two different echo commands
                   #     to diff.

或者，您可能希望使 file1 看起来像 file2，每个数字在不同的行上。这将产生更有用的差异输出。

$ diff -u <(printf '%s\n' $(< file1)) <(printf '%s\n' $(< file2))
--- /dev/fd/63  2012-09-10 23:55:30.000000000 -0400
+++ file2   2012-09-10 23:47:24.000000000 -0400
@@ -1,7 +1,7 @@
 1
 2
-3
 4
+3
 5
 6
 7

这类似于将 echo 更改为 printf '%s\n' 以在每个单词后放置一个换行符的第一个命令。

注意:如果比较的文件过长，这两个命令都会失败。这是因为命令行长度的限制。如果发生这种情况，那么您将需要解决此限制，例如将 echo/printf 的输出存储到临时文件中。