CODEWITHSUNDEEP
pythonpython-3.xsubprocess
user9614249
user9614249

Reputation:

Capture output from subprocess with a timeout set

I am using subprocess.run to run a command and capture the output like so:

proc = subprocess.run([commandAndFlags], capture_output=True)

if proc.stdout:
    print('stdout:', str(proc.stdout))
if proc.stderr:
    print('stderr:', str(proc.stderr))

I would like to add a timeout, but still capture any output sent to stdout/stderr before the timeout goes off.

However, if I simple add the timeout and wrap it in a try/except, I cannot capture the subprocess output.

try:
    proc = subprocess.run([commandAndFlags], capture_output=True, timeout=2000)
except subprocess.TimeoutExpired:
    print('Timeout!!')

if proc.stdout:
    print('stdout:', str(proc.stdout))
if proc.stderr:
    print('stderr:', str(proc.stderr))

Now proc is not defined when I try to print stdout/stderr.

How can I set a timeout but still capture any output that was printed before the timeout?

Upvotes: 3

Views: 1789

Answers (2)

Chris
Chris

Reputation: 1321

You can still use the capture_output attribute from your original code, and when the TimeoutExpired exception is thrown, you can collect stdout and stderr from there. For example:

try:
    proc = subprocess.run([commandAndFlags], capture_output=True, text=True, timeout=2000)
    outs = proc.stdout
    errs = proc.stderr
except subprocess.TimeoutExpired as timeErr:
    outs = timeErr.stdout
    errs = timeErr.stderr

Upvotes: 5

user9614249
user9614249

Reputation:

Eventually I figured out that you can pass files directly to subprocess.run.

outfile = 'outfile.txt'
errfile = 'errfile.txt'
try:
  proc = subprocess.run([commandAndFlags], timeout=2000
                        stdout=open(outfile, 'w'), stderr=open(errfile, 'w'))
except subprocess.TimeoutExpired:
    print('Timeout!!')

# check if outfile/errfile files exist and print contents

subprocess will save stdout/stderr directly to a file that can be viewed later, regardless of if the subprocess was stopped by a timeout.

Upvotes: 0

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