做一个 tail -F 直到匹配一个模式 [英] Do a tail -F until matching a pattern

问题描述

我想对文件执行 tail -F 直到匹配模式.我找到了一种使用 awk 的方法，但恕我直言，我的命令并不是很干净.问题是由于某些限制，我需要只在一行中完成.

I want to do a tail -F on a file until matching a pattern. I found a way using awk, but IMHO my command is not really clean. The problem is that I need to do it in only one line, because of some limitations.

tail -n +0 -F /tmp/foo | 
awk -W interactive '{if ($1 == "EOF") exit; print} END {system("echo EOF >> /tmp/foo")}'

尾部将阻塞，直到 EOF 出现在文件中.它工作得很好.END 块是强制性的，因为 awk 的 exit 不会立即退出.在退出之前，它使 awk 成为 eval END 块.END 块挂在读取调用上(因为 tail)，所以我需要做的最后一件事是在文件中写入另一行以强制 tail 退出.

The tail will block until EOF appears in the file. It works pretty well. The END block is mandatory because awk's exit does not exit right away. It makes awk to eval the END block before quitting. The END block hangs on a read call (because of tail), so the last thing I need to do, is to write another line in the file to force tail to exit.

有人知道更好的方法吗?

Does someone know a better way to do that?

推荐答案

试试这个:

sh -c 'tail -n +0 -f /tmp/foo | { sed "/EOF/ q" && kill $$ ;}'

只要EOF"出现，整个命令行就会退出.字符串可见于 /tmp/foo.

The whole command-line will exit as soon as the "EOF" string is seen in /tmp/foo.

有一个副作用:tail 进程将一直运行(在后台)，直到将任何内容写入 /tmp/foo.

There is one side-effect: the tail process will be left running (in the background) until anything is written to /tmp/foo.

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