'xcrun xctrace list devices' gives list of devices info in stderr - Python

Hi Sivaji_SE,

That's unexpected. Can you please provide some steps to reproduce it? How are you running the xctrace tool?

Same in java and common terminal execution, just redirect error stream to a file.

To reproduce in java, just create ProcessBuilder with proper command and start it.
To read stream I used:

Code Block 
import org.apache.commons.io.IOUtils;
IOUtils.readLines(process.getInputStream(), encoding)

InputStream returns nothing, while all output is in error stream.


I had also problems with output encoding. On my local machine output was in UTF16LE encoding for some reason, while on other machines it was in UTF8

I was trying to get the information of all ios real devices (connected to my machine) and also the simulators.

import subprocess

def getdeviceinfo(self):
alldevicesinfo = subprocess.run(['xcrun', 'xctrace', 'list', 'devices'], stdout=subprocess.PIPE).stdout.decode(
'utf-8')

The above process gives me the o/p as an empty string but, gives the expected information in stderr (in the error)


Try the below code:
alldevicesinfo = subprocess.run(['xcrun', 'xctrace', 'list', 'devices'], stderr=subprocess.PIPE).stderr.decode(
'utf-8')

I had the same problem and solved it by redirecting stderr to stdout with xcrun xctrace list devices 2>&1

You could also use

import subprocess

completed_process = subprocess.run(['xcrun', 'xctrace', 'list', 'devices'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
all_devices_info = completed_process.stderr.decode('utf-8')