Question

hello i在“灰色”处理模块中有问题

我想与儿童进程互动(ex:儿童发育、辍学)。

这是儿童方案法典。

  1 #include <stdio.h>
  2 
  3 int main(){
  4         char buf[1024];
  5         printf("asdfsadfasff
");
  6         scanf("%s",buf);
  7         printf("%s
",buf);
  8 }

该守则非常简单,印刷了插图、等待投入和印刷投入,以显示:

下面是《 p法》。

  1 #!/usr/bin/python
  2 from subprocess import *
  3 
  4 fd = Popen(["./random"],stdin=PIPE,stdout=PIPE)
  5 print "pid = %d"%(fd.pid) # print pid
  6 result = ""
  7 result = fd.stdout.read(-1) # read
  8 print result
  9 fd.stdin.write("write write write!!!
")
 10 result = fd.stdout.read(-1)
 11 print result

在这种情况下,我预计这一方案将很好地发挥作用,但第7行(fd.stdout.read(-1)被封锁,从来不工作。

我将职能部分改为职能部分(改为(-1),改为(1),改为(1024),但所有工作都不奏效。

但是,在先给予扼杀时,方案是行之有效的。

我认为,当方案结束时,儿童 st忙的缓冲未能补足...... 这只是我的意见。

这一问题是否有任何解决办法?

Edit1. when I execute program which is print string first, and wait user s input such as "sudo su" This worked well that I expected

我无法理解为什么这一案件运作良好。

  1 from subprocess import *
  2 
  3 fd = Popen(["sudo","su"],stdin=PIPE,stdout=PIPE)
  4 
  5 print fd.stdout.read(-1)
  6 print fd.stdin.write("asdfasdfas
")

Answer 1

The child process ./random is using stdio, which by default does "full buffering" rather than "line buffering" when the process s stdout is not a tty device. Since python runs the process via pipes (which are not tty devices) the program is buffering its output, and not printing it at the time of the scanf call. The buffer is flushed (written to stdout) only (a) when it fills up; (b) when explicitly flushed with an fflush call; or (c) at program exit.

您可修改儿童程序,以明确fflush。电话或您可使用一种pseudo-tty,例如,pexpect或sh <<<>>>>>>><<>>>>>>><>><>>>>><>>><>>>>>>>>>>>>><>>>>>>><>>>>>><>>>>>>>>>>>>><>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> (说明<代码>sh 模块因缺省而只使用一定数量的产出,但通常足够。或者,在这样的情况下,如果你只管理“互动”方案(但实际上完全可以预测),那么你就能够按事先规定的已知投入顺序进行:

fd = Popen(["./random"], stdin=PIPE, stdout=PIPE)
result = fd.communicate("write write write!!!
")[0]

虽然你当然会把所有排他性投入混为一谈,并且必须将其印刷的两条线分开(就本案而言)。

友情链接