Broken pipe from subprocess .Popen.communciate () with stdin

Question

I am having a strange problem when using subprocess.Popen.communicate (). For background, I want to execute an application from my python script. When I run the program from the command line, I do it like this (UNIX):

$ echo "input text" | / path / to / myapp

From my script, I also want to pass the input to the application. So, I tried the following. But I get a “broken pipe” error when I try to send an input with a message ():

>>> cmd = ['/ path / to / myapp']
>>> p = subprocess.Popen (cmd, stdout = subprocess.PIPE, stderr = subprocess.STDOUT, stdin = subprocess.PIPE)
>>> out, err = p.communicate ('input text')
Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/lib/python2.5/subprocess.py", line 670, in communicate
    return self._communicate (input)
  File "/usr/lib/python2.5/subprocess.py", line 1223, in _communicate
    bytes_written = self._write_no_intr (self.stdin.fileno (), buffer (input, input_offset, 512))
  File "/usr/lib/python2.5/subprocess.py", line 1003, in _write_no_intr
    return os.write (fd, s)
OSError: [Errno 32] Broken pipe

To make the situation stranger, if I don't leave the input, I don't get any errors. However, this is not a good way, because the application requires input to work.

>>> p = subprocess.Popen (cmd, stdout = subprocess.PIPE, stderr = subprocess.STDOUT, stdin = subprocess.PIPE)
>>> out, err = p.communicate ()
>>> print out
[error from myapp regarding lack of input]

, ?

Answer 1

, myapp () . myapp, , , ,

$ echo 'hello world' | tr 'l' 'L'
heLLo worLd

...

>>> cmd = ['/usr/bin/tr']
>>> p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, stdin=subprocess.PIPE)
>>> out,err = p.communicate('hello world')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/subprocess.py", line 668, in communicate
    return self._communicate(input)
  File "/usr/lib/python2.5/subprocess.py", line 1218, in _communicate
    bytes_written = self._write_no_intr(self.stdin.fileno(), buffer(input, input_offset, 512))
  File "/usr/lib/python2.5/subprocess.py", line 997, in _write_no_intr
    return os.write(fd, s)
OSError: [Errno 32] Broken pipe

...

>>> p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
>>> /usr/bin/tr: missing operand
Try `/usr/bin/tr --help' for more information.

:

>>> cmd = ['/usr/bin/tr', 'l', 'L']
>>> p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
>>> out,err = p.communicate('hello world')>>> print out
heLLo worLd
>>> print err
None

... . , stderr - myapp...?