如何将前N个字节从文本文件移动到另一个文本文件 [英] How to move first N bytes from text file to another text file

问题描述

我遇到了一个极端问题，我能想到的所有解决方案都很复杂。根据我的UNIX / Linux经验，必须有一种简单的方法。

I've got an extreme problem, and all of the solutions I can imagine are complicated. According to my UNIX/Linux experience there must be an easy way.

我要删除log.txt.file中文件的前n个字节足够长。好吧，我敢肯定有人会为我提供一个我无法想象的简单的解决方案。

I want to delete the first n bytes of file in log.txt.file is long enough. Well, I'm sure somebody will deliver me a suprisingly easy solution I just can't imagine.

推荐答案

将 tail 与 -c 选项一起使用怎么办

What about using tail with it's -c option

from man：

 -c, --bytes=K
          output the last K bytes; alternatively, use -c +K to output bytes starting with the Kth of each file

像
tail -c + N log.txt.file

so you can do something like tail -c +N log.txt.file

 where N is the Number of bytes to delete

示例：

 [prompt]$ cat file
 ABCDEFGH
 [prompt]$ tail -c +2 file                      //output bytes starting from the second byte
 BCDEFGH
 [prompt]$ tail -c +3 file                     //output bytes starting from the third byte
 CDEFGH
 [prompt]$ tail -c +5 file                     //output bytes starting from the fifth byte
 EFGH

 [prompt]$ ls -l
 -rw-r--r-- 1 user users 9 2014-08-07 10:22 file         // 9 bytes
 [prompt]$ tail -c +S file >> file2                      //this will copy file content to file2 escaping the first 4 bytes
 [prompt]$ ls -l file2                                   
 -rw-r--r-- 1 user users 5 2014-08-07 10:29 file2         // 5 bytes (9 - first 4 bytes)

我不得不提到您可以也使用-bytes 选项从文件中获取最后N个字节。

i have to mention that you can use also --bytes option to get the last N bytes from a file.

  [prompt]$ tail --bytes=5 file              //print the last 5 bytes
  EFGH

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