无法创建/dev/stdout:没有这样的设备或地址 [英] cannot create /dev/stdout: No such device or address

问题描述

我想通过node运行shell命令并捕获stdout的结果.我的脚本可以在OSX上正常运行，但不能在Ubuntu上运行.

I'm want to run a shell command via node and capture the result of stdout. My script works fine on OSX, but not on Ubuntu.

我已将问题和脚本简化为以下节点脚本:

I've simplified the problem and script to the following node script:

var execSync = require('child_process').execSync,
    result = execSync('echo "hello world" >> /dev/stdout');

// Do something with result

结果:

/bin/sh:1:无法创建/dev/stdout:没有此类设备或地址

/bin/sh: 1: cannot create /dev/stdout: No such device or address

• 我尝试用/dev/fd/1
替换/dev/stdout
• 我尝试将shell更改为bash ... execSync('echo ...'，{shell:'/bin/bash'})

就像我说的那样，上面的问题得到了简化.真实的脚本接受应在其中写入结果的文件的名称作为参数，因此我需要通过提供对stdout流作为文件描述符的访问来解决此问题，即/dev/stdout .

Like I said, the problem above is simplified. The real script accepts as a parameter the name of a file where results should be written, so I need to resolve this by providing access to the stdout stream as a file descriptor, i.e. /dev/stdout.

我如何通过节点执行命令，同时赋予命令对自己的 stdout流的访问权限?

How can I execute a command via node, while giving the command access to its own stdout stream?

推荐答案

在/dev/stdout

我无权访问OSX机器，而是从此问题访问在 phantomjs 上，似乎在OSX/BSD和Linux上，/dev/stdout 都是符号链接，但是它们之间的工作方式似乎有所不同.其中一位评论者说，在OSX上使用/dev/stdout 是标准的，但在Linux上则不使用.在另一个随机位置中，我读到这样的语句:暗示/dev/stdout 几乎是OSX的东西.在此答案中可能有一个线索关于为什么它在Linux上不起作用的提示(似乎隐式关闭文件描述符)当以这种方式使用时.)

On /dev/stdout

I don't have access to an OSX box, but from this issue on phantomjs, it seems that while on both OSX/BSD and Linux /dev/stdout is a symlink, nonetheless it seems to work differently between them. One of the commenters said it's standard on OSX to use /dev/stdout but not for Linux. In another random place I read statements that imply /dev/stdout is pretty much an OSX thing. There might be a clue in this answer as to why it doesn't work on Linux (seems to implicitly close the file descriptor when used this way).

其他相关问题:

• https://unix.stackexchange.com/questions/36403/portability-of-dev-stdout
• bash重定向到/dev/stdout:不是目录

我在Arch上尝试了您的代码，确实给了我同样的错误，就像上面提到的变体一样-因此这与Ubuntu无关.

I tried your code on Arch and it indeed gives me the same error, as do the variations mentioned - so this is not related to Ubuntu.

我找到了博客文章，其中介绍了如何将文件描述符传递给 execSync .将其与我从此处所获得的内容一起此处，我编写了此代码的修改后的版本:

I found a blog post that describes how you can pass a file descriptor to execSync. Putting that together with what I got from here and here, I wrote this modified version of your code:

var fs = require('fs');
var path = require('path');

var fdout = fs.openSync(path.join(process.cwd(), 'stdout.txt'), 'a');
var fderr = fs.openSync(path.join(process.cwd(), 'stderr.txt'), 'a');

var execSync = require('child_process').execSync,
    result = execSync('echo "hello world"', {stdio: [0,fdout,fderr] });

除非我误解了您的问题，否则您希望能够更改 execSync 中命令输出的位置.这样就可以使用文件描述符了.如果希望被调用的程序输出到由继承的 stdout 和 stderr ，则仍可以传递 1 和 2 它的父级，您已经在评论中提到了.

Unless I misunderstood your question, you want to be able to change where the output of the command in execSync goes. With this you can, using a file descriptor. You can still pass 1 and 2 if you want the called program to output to stdout and stderr as inherited by its parent, which you've already mentioned in the comments.

供以后参考，该版本适用于内核版本为 4.10.9-1-ARCH 的Arch，版本为 bash 4.4.12 和 node v7.7.3 .

For future reference, this worked on Arch with kernel version 4.10.9-1-ARCH, on bash 4.4.12 and node v7.7.3.

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