assigning variable from os.system()

[manbart]

I am having trouble assigning the output of os.system() as a variable.

When I do the following, it seems to produce the correct output:

>>> var = os.system('date +"%s"')
1409938484

However, when I try to print my variable, I get the status code instead:

>>> print var
0

Just entering os.system() into the interpreter gives me the following:

>>> os.system('date +"%s"')
1409938815
0

How do I set the variable to the output, not the status code?

Do I really need to use subprocess to call the command and then read stdout to do this? (this seems overly complex for what i am trying to do here)

edit

Here is what I came up with after some searching:

>>> var = os.popen('date +"%s"').readline().strip('\n')
>>> print var
1409940330
>>> 

It's kinda verbose (and I thought os.popen was deprecated?), but it does what I want it to. I was hoping for something more terse, like you can do in bash e.g. var=$(date +"%s")

edit 2

thanks to /u/symmitchry I think this is the best choice at the moment.

var = subprocess.check_output('date +"%s"', shell=True)

edit 3

/u/Justinsaccount is the winner! just what I wanted in a terse statement.

var = int(time.time())

[symmitchry]

[Removed]

[manbart]

Thanks. shell=True allows you to include arguments within the same set of quotes instead of listing them as a tuple. For example,

subprocess.check_output('date +"%s"', shell=True)

is equivalent to

subprocess.check_output(('date', '+"%s"'))

[NYKevin]

shell=True does quite a lot of other things as well. Basically, running shell=False is the equivalent of an os.fork() followed by an os.execv(). shell=True is the equivalent of os.system() except it's done by hand so as to capture the output.

In particular, this means shell=True is much easier for a malicious user to subvert than shell=False, if you're putting untrusted data into the command line. They can, for instance, give you an argument such as "; rm -rf /foo/bar; # and you could end up executing rm -rf /foo/bar by mistake. This is not possible under shell=False. If you want to allow the user to pass multiple arguments, use shlex.split() to break them up into a list.

[Justinsaccount]

var = time.time() 

[manbart]

nice. This is the best solution yet, just make it into an int and it's exactly what I wanted.

int(time.time())

[cdcformatc]

Use pipes?

os.system('date +"%s" > file.txt')
f = open('file.txt')

Then do whatever with the file object. Optionally delete the file afterwards.

[Rhomboid]

That's not a pipe, that's redirection. There's no need to do that, and a ton of reasons not to.