如何阻止管道直到模式匹配？

【问题标题】：How can I block a pipe until a pattern match?如何阻止管道直到模式匹配？
【发布时间】：2016-02-12 09:54:21
【问题描述】：

如何在匹配模式之前阻塞管道？我想做这样的事情：

#!/bin/sh

mkfifo request response
while true; do # needs to send one response at a time
  nc -N -l 127.0.0.1 4000 >request <response & # send output to request pipe
  sed -u '/^$/q' <request; # block until a blank line is received
  date | tee response # send input back to the original command
done

【问题讨论】：

标签： unix pipe sh named-pipes

【解决方案1】：

如果匹配模式的操作是阻塞的，cat 可以用来防止数据从命名管道中出来，直到有东西被写入它。 cat 将从命名管道中读取数据，直到将 EOF 写入其中。

#!/bin/sh

mkfifo response
while true; do # send one response at a time
  cat response | nc -N -l 127.0.0.1 4000 | # pipe request out
  (
    sed -u '/^$/q' # block until a blank line is received
    date | tee response # send input back to the original command
  )
done

【讨论】：