Question

下面的代码有两个问题。任何人都可以帮忙吗？

如何返回[captured_stdout，captured_stderr]的值？
当在popen3中使用puts时，ruby在打印后不会返回提示。我该如何解决这个问题？

== code

#!/bin/env ruby

require 'open3'
require 'etc'

def as_user(user, &block)
  u = Etc.getpwnam(user)
  Process.fork do
      Process.uid = u.uid
      block.call(user)
  end
end

def run_cmd(cmd)
  as_user "oracle" do |user|
    puts("In block as #{user} (uid=#{Process.uid}), pid is #{Process.pid}")
    Open3.popen3(cmd) do |i,o,e,wait_thr|
        stdout = o.read
        stderr = e.read
        [stdout, stderr]
    end
  end
end

output = run_cmd("/bin/date")
puts output

==输出

[root@test]# ./x2.rb
24810
In block as oracle (uid=1001), pid is 24810
[root@test]#

Answer 1

我不认为你应该从方法返回，直到popen方法调用（包括你指定的块）完成。如果这是真的，那么您需要在调用popen之前声明这些返回变量，然后仅在popen完成后返回它们。像这样：

def run_cmd(cmd)
  as_user "user1" do |user|
    puts("In block as #{user} (uid=#{Process.uid}), pid is #{Process.pid}")

    captured_stdout = captured_stderr = nil  # just to declare them

    Open3.popen3(cmd) do |i,o,e,wait_tnr|
       captured_stdout = o.read
       captured_stderr = e.read

       i.close
       o.close
       e.close

    end
    [captured_stdout, captured_stderr]
  end
end

顺便问一下，你确定要使用Ruby 1.8吗？它现在非常古老，并且在很长一段时间内都没有得到支持。

考虑到这一点，删除本地captured_变量和close调用可以大大简化：

def run_cmd(cmd)
  as_user "user1" do |user|
    puts("In block as #{user} (uid=#{Process.uid}), pid is #{Process.pid}")
    Open3.popen3(cmd) { |i,o,e,wait_tnr| [o.read, e.read] }
  end
end

为了加强这一点，您可能希望添加一个线程连接，以便在命令关闭其stdout然后需要运行一段时间之后，它会有时间完成其工作：

def run_cmd(cmd)
  as_user "user1" do |user|
    puts("In block as #{user} (uid=#{Process.uid}), pid is #{Process.pid}")
    Open3.popen3(cmd) do |i,o,e,wait_tnr|
      stdout = o.read
      stderr = e.read
      wait_thr.join
      [stdout, stderr]
    end
  end
end

fork问题，返回值并返回提示

1 个答案: