Raising exception on STDIN read

[Michael Goerz]

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?

Thanks,
Michael

[Gabriel Genellina]

En Wed, 27 Feb 2008 15:06:36 -0200, Ian Clark <ic****@mail.ewu.edu>
escribi�:

On 2008-02-27, Michael Goerz <ne**************@8439.e4ward.comwrote:

>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.

Try with stdin=open("/dev/full") or stdin=open("/dev/null")

--
Gabriel Genellina

[Michael Goerz]

Gabriel Genellina wrote, on 02/27/2008 03:26 PM:

En Wed, 27 Feb 2008 15:06:36 -0200, Ian Clark <ic****@mail.ewu.edu>
escribi�:

>On 2008-02-27, Michael Goerz <ne**************@8439.e4ward.comwrote:

>>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.

Try with stdin=open("/dev/full") or stdin=open("/dev/null")

using /dev/null works in my specific case (in my posted minimal example
I still have to press Enter, but in the real program it causes pdflatex
to fail, like I want it to). However, the solution is limited do Linux,
as on Windows there's no /dev/null. Is there a platform independent
solution?
Michael

[Grant Edwards]

On 2008-02-27, Michael Goerz <ne**************@8439.e4ward.comwrote:

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?

If I were you, I'd just run LaTeX in batch mode. That's what I
always used to do when automating the running of LaTeX using a
shell script or makefile. IIRC, you do something like this:

ret = os.system("latex \\batchmode\\input %s" % filename)

The return status will be zero for success and non-zero if
there were any errors.

--
Grant Edwards grante Yow! Remember, in 2039,
at MOUSSE & PASTA will
visi.com be available ONLY by
prescription!!

[Michael Goerz]

Grant Edwards wrote, on 02/27/2008 04:34 PM:

On 2008-02-27, Michael Goerz <ne**************@8439.e4ward.comwrote:

>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?

If I were you, I'd just run LaTeX in batch mode. That's what I
always used to do when automating the running of LaTeX using a
shell script or makefile. IIRC, you do something like this:

ret = os.system("latex \\batchmode\\input %s" % filename)

Yeah, I'm doing that by default. The problem in my actual program is
that the user can change the latex command and the compiler options, so
I can't guarantee that the latex compiler is being run in batchmode or
nonstopmode (The user might screw up). So, ideally, I want to enforce
that the subprocess is non-interactive by trowing an exception if it
does ask for input.

I have to use subprocess instead of os.system because I want to filter
the output (colorize it, parse for warnings, etc.)

Thanks,
Michael

[Gabriel Genellina]

En Wed, 27 Feb 2008 18:59:59 -0200, Michael Goerz
<ne**************@8439.e4ward.comescribi�:

>Try with stdin=open("/dev/full") or stdin=open("/dev/null")

using /dev/null works in my specific case (in my posted minimal example
I still have to press Enter, but in the real program it causes pdflatex
to fail, like I want it to). However, the solution is limited do Linux,
as on Windows there's no /dev/null. Is there a platform independent
solution?

It's spelled "NUL" on Windows; os.devnull returns the right thing
depending on the platform.

--
Gabriel Genellina

[Ian Clark]

On 2008-02-28, Gabriel Genellina <ga*******@yahoo.com.arwrote:

I hope it's more clear now. Python objects are only meaningful *inside* a
Python program, but an *external* program can't use them directly.

Yes, sorry. This is what I was getting hung up on. My thinking was that
subprocess was orchestrating it such that any reads would be funneled
back into the Python object. Granted, that was my gut reaction to it.
Thinking (and playing) with it a bit more I now realize that that makes
no sense. Thank you for reminding me about the seperation of OS and
Python files.

Ian