Redirect subprocess stderr to stdout

Question

I want to redirect the stderr output of a subprocess to stdout. The constant STDOUT should do that, shouldn\'t it?

However,

$ python >/dev/null -c         


        

Answer 1

Actually, using subprocess.STDOUT does exactly what is stated in the documentation: it redirects stderr to stdout so that e.g.

proc = subprocess.Popen(self.task["command"], shell=False, bufsize=1, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
output = ""
while (True):
    # Read line from stdout, break if EOF reached, append line to output
    line = proc.stdout.readline()
    line = line.decode()
    if (line == ""): break
    output += line

results in variable output containing the process' output from both stdout and stderr.

stderr=subprocess.STDOUT redirects all stderr output directly to stdout of the calling process, which is a major difference.