为什么不“对文件1排序"文件1"工作? [英] Why doesn't "sort file1 > file1" work?

问题描述

当我尝试对文件进行排序并将排序后的输出保存在自身中时，就像这样

When I am trying to sort a file and save the sorted output in itself, like this

sort file1 > file1;

file1的内容将被完全删除，而当我尝试使用像这样的'tee'命令进行同样的操作

the contents of the file1 is getting erased altogether, whereas when i am trying to do the same with 'tee' command like this

sort file1 | tee file1;

它可以正常工作 [ed:仅对具有幸运时机的小型文件有效，会导致大型文件丢失或无用的进程调度而导致数据丢失] ，即它将覆盖已排序的输出file1本身，并在标准输出中显示它.

it works fine [ed: "works fine" only for small files with lucky timing, will cause lost data on large ones or with unhelpful process scheduling], i.e it is overwriting the sorted output of file1 in itself and also showing it on standard output.

有人可以解释为什么第一种情况不起作用吗?

Can someone explain why the first case is not working?

推荐答案

它不起作用，因为'>'重定向意味着会被截断，并且在将sort的整个输出保留在内存中之前，请先将其重定向到在运行sort之前，bash会截断文件并重定向输出.因此，file1文件的内容将在sort有机会阅读之前被截断.

It doesn't work because '>' redirection implies truncation, and to avoid keeping the whole output of sort in the memory before re-directing to the file, bash truncates and redirects output before running sort. Thus, contents of the file1 file will be truncated before sort will have a chance to read it.

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