Raising exception on STDIN read
Ian Clark
iclark at mail.ewu.edu
Thu Feb 28 11:29:04 EST 2008
On 2008-02-27, Gabriel Genellina <gagsl-py2 at yahoo.com.ar> wrote:
> En Wed, 27 Feb 2008 15:06:36 -0200, Ian Clark <iclark at mail.ewu.edu>
> escribi�:
>
>> On 2008-02-27, Michael Goerz <newsgroup898sfie at 8439.e4ward.com> wrote:
>>> Hi,
>>>
>>> I would like to raise an exception any time a subprocess tries to read
>>> from STDIN:
>>>
>>> latexprocess = subprocess.Popen( \
>>> 'pdflatex' + " " \
>>> + 'test' + " 2>&1", \
>>> shell=True, \
>>> cwd=os.getcwd(), \
>>> env=os.environ, \
>>> stdin=StdinCatcher() # any ideas here?
>>> )
>>>
>>> An exception should be raised whenever the pdflatex process
>>> reads from STDIN... and I have no idea how to do it. Any suggestions?
>
>> How about with a file-like object? I haven't tested this with subprocess
>> so you might want to read the manual on files if it doesn't work[1].
>
> Won't work for an external process, as pdflatex (and the OS) knows nothing
> about Python objects. The arguments to subprocess.Popen must be actual
> files having real OS file descriptors.
Taken from the subprocess documentation (emphasis mine). [1]
stdin, stdout and stderr specify the executed programs' standard
input, standard output and standard error file handles,
respectively. Valid values are PIPE, an existing file descriptor (a
positive integer), *an existing file object*, and None.
The following peice of code works fine for me with the subprocess
module. NOTE: the only difference from this and the last I posted is
that I set fileno() to _error().
import sys
import subprocess
class ErrorFile(object):
def _error(self, *args, **kwargs):
raise AssertionError("Illegal Access")
def _noop(self, *args, **kwargs):
pass
close = flush = seek = tell = _noop
next = read = readline = readlines = xreadlines = tuncate = _error
truncate = write = writelines = fileno = _error
# ^^^^^^
proc = subprocess.Popen("cat -", shell=True, stdin=ErrorFile())
ret = proc.wait()
print "return", ret
Ian
[1] http://docs.python.org/lib/node528.html
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