bash 用于截断大文件的Unix shell脚本
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Unix shell script to truncate a large file
提问by peedee
I am trying to write a Unix script which will truncate/empty a file which is continuously being written/open by an application when it reaches say 3GB of space. I know that the below command would do it :
我正在尝试编写一个 Unix 脚本，当它达到 3GB 空间时，它将截断/清空应用程序不断写入/打开的文件。我知道下面的命令可以做到：
cp /dev/null [filename]
But I am going to run this in an production environment automatically as a cron job - just posting here to see if you guys faced any issues while doing something similar to this.
但是我将在生产环境中自动运行它作为 cron 作业 - 只是在这里发布看看你们在做类似的事情时是否遇到任何问题。
回答by chepner
Just to add another answer,
只是为了添加另一个答案，
: > filename
:is a no-op in bash (POSIX-compliant), so this essentially just opens the file for writing (which of course truncates the file) and then immediately closes it.
:是 bash 中的无操作（符合 POSIX 标准），因此这实际上只是打开文件进行写入（当然会截断文件），然后立即关闭它。
EDIT: as shellter commented, you don't actually need a command to go along with the redirection:
编辑：正如 shellter 所评论的，你实际上不需要一个命令来进行重定向：
$ echo foo > foo.txt
$ cat foo.txt
foo
$ > foo.txt
$ cat foo.txt
$
A simple redirection all by itself will clear the file.
一个简单的重定向本身将清除文件。
回答by Ricardo Marimon
I've used the following command on debian
我在 debian 上使用了以下命令
truncate -s 0 filename
回答by Don Branson
That seems reasonable to me. Unix, of course, would let you do this about 50 different ways. For example,
这对我来说似乎是合理的。当然，Unix 可以让您以大约 50 种不同的方式执行此操作。例如，
echo -n "" >filename
cat /dev/null >filename
回答by San
trunc filename
trunc filename
works on AIX flavor of UNIX
适用于 AIX 风格的 UNIX
