建立管道从命名管道读取，而不在bash阻塞 [英] Setting up pipelines reading from named pipes without blocking in bash

问题描述

我期待与调用打开一个给定的管道文件描述符一个子进程使得open（）调用不挂在等待管道的另一端接收的连接。

I'm looking to call a subprocess with a file descriptor opened to a given pipe such that the open() call does not hang waiting for the other side of the pipe to receive a connection.

要证明：

$ mkfifo /tmp/foobar.pipe
$ some_program --command-fd=5 5</tmp/foobar.pipe

在这种情况下， some_program 不运行，直到一些过程有 /tmp/foobar.pipe 打开写;然而， some_program ，即使它不接收命令有一些有用的效果，所以期望的行为是 some_program 来立即执行

In this case, some_program is not run until some process has /tmp/foobar.pipe open for write; however, some_program has useful effects even when it isn't receiving commands, so desired behavior is for some_program to be immediately executed.

机制通过备用脚本语言exec'ing（蟒蛇，perl的，等等）或C封装程序打开 /tmp/foobar.pipe 通过这样做 O_NONBLOCK 标志明显;我在寻找一个纯bash的解决方案，应该是可能的。

Mechanisms to do this by exec'ing through an alternate scripting language (python, perl, etc) or a C wrapper which open /tmp/foobar.pipe with the O_NONBLOCK flag are obvious; I'm looking for a pure-bash solution, should one be possible.

推荐答案

打开FD读/设置当管道prevents阻塞写，而不是只读的。

Opening the FD read/write rather than read-only when setting up the pipeline prevents blocking.

要成为一个更具体一点：

To be a bit more specific:

$ mkfifo /tmp/foobar.pipe
$ some_program --command-fd=5 5<>/tmp/foobar.pipe

prevents不需要的阻塞行为，如 5℃;＆GT; /tmp/foobar.pipe 在RW模式打开（如只读模式而不是开放与 5℃/tmp/foobar.pipe ），尽​​管 O_NONBLOCK 仍设置。由于瓦尔德纳在IRC：//irc.freenode.org/#bash该指针

prevents the undesired blocking behavior, as 5<>/tmp/foobar.pipe opens in RW mode (as opposed to opening in read-only mode as with 5</tmp/foobar.pipe) although O_NONBLOCK is still set. Thanks to waldner on irc://irc.freenode.org/#bash for this pointer.

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