How to read output from subprocess without printing to terminal?

Question

I've searched fairly thoroughly for an answer, but haven't found any solutions to this.

I need to execute a child process only momentarily to print its version information. If run from the command line, it's simply

.\bin\application.exe --version

and version information is printed to the terminal. I'd like to capture that information in a string. I've been trying out variants of

args = ("path\to\application.exe", "--version")
subprocess.Popen(args, stdout=subprocess.PIPE).communicate()[0]

with no success. I also need this not to print the output to the terminal, if possible. What can I do?

Is the application printing the version information to STDERR? Try adding stderr=subprocess.STDOUT to your Popen call and see what happens. — Sam Mussmann
– Sam Mussmann, Commented Feb 14, 2014 at 20:34
Glad to help! I added an answer for better visibility for people who come across this question later. — Sam Mussmann
– Sam Mussmann, Commented Feb 14, 2014 at 20:44
note: if you want to discard the output then you should use DEVNULL instead of PIPE otherwise you can run out of memory if the child process generates enough output. — jfs
– jfs, Commented Feb 18, 2014 at 9:47

Sam Mussmann · Accepted Answer · 2014-02-14 20:43:57Z

3

Sometimes applications dump version information to STDERR instead of STDOUT.

You can capture both like this:

args = ("path\to\application.exe", "--version")
subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT).communicate()[0]

answered Feb 14, 2014 at 20:43

Sam Mussmann

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