Python subprocess.call error message with check_output

Question

So I have:

result = subprocess.check_output(['wine',
                    os.getcwd()+'/static/sigcheck.exe',
                    '-a','-i','-q',
                    self.tmpfile.path()])

But whenever I run this I get this error

CalledProcessError: Command '['wine', '/home/static/sigcheck.exe', '-a', '-i', '-q',     '/tmp/tmpxnsN5j']' returned non-zero exit status 1

But if I change check_output to call it works fine:

Z:\tmp\tmpvOybcm:
    Verified:       Unsigned
    File date:      9:08 AM 10/24/2012
    Publisher:      Hardcore Computer
    Description:    Farthest Emitters Converter
    Product:        Farthest Emitters Converter
    Version:        3.2.0
    File version:   3.2.0
fixme:mscoree:StrongNameSignatureVerificationEx (L"Z:\\tmp\\tmpvOybcm", 1, 0x33ec13): stub
    Strong Name:    Unsigned
    Original Name:  n/a
    Internal Name:  Farthest Emitters Converter
    Copyright:      Hardcore Computer 2006
    Comments:       n/a

Any reason why check_output wouldn't work?

wim · Accepted Answer · 2012-10-24 13:12:58Z

6

A non-zero return code is (usually) a way of indicating exit with error by a program. So subprocess.check_output will raise an exception if the returncode of the process is non-zero. If you use:

retcode = call(...)

and then print the return code I guess you will see that it is returning 1.

answered Oct 24, 2012 at 13:12

wim

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2 Comments

Stupid.Fat.Cat Over a year ago

is there a way to capture the output into a variable?

wim Over a year ago

You can use check_output in a try: block and Except CalledProcessError:, but the usual way is just to make a subprocess.Popen object with pipes for stdout, stderr and then use it's communicate method.

jfs · Accepted Answer · 2012-10-24 13:21:13Z

3

To get output in a string without raising an error on non-zero exit status:

p = Popen(['wine',...], stdout=PIPE)
output = p.communicate()[0]

check_output() executes rc = p.poll() after p.communicate() and raises an error if bool(rc) == True.

answered Oct 24, 2012 at 13:21

jfs

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Comments

SWAPYAutomation · Accepted Answer · 2012-10-24 13:19:29Z

1

Alternative way

proc = subprocess.Popen(['wine',
                    os.getcwd()+'/static/sigcheck.exe',
                    '-a','-i','-q',
                    self.tmpfile.path()], stdin=subprocess.PIPE,  stdout=subprocess.PIPE)
stdout = proc.stdout.read()

answered Oct 24, 2012 at 13:19

SWAPYAutomation

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2 Comments

wim Over a year ago

It is preferred to use communicate() rather than .stdout.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.

SWAPYAutomation Over a year ago

Roger. Thanks for the warning

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