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I'm running a script that executes a number of executables by using
subprocess.call(cmdArgs,stdout=outf, stderr=errf)
when outf/errf is either None or a file descriptor (different files for stdout/stderr).
Is there any way I can execute each exe so that the stdout and stderr will be written to the files and terminal together?
960
To capture the output of the subprocess. run method, use an additional argument named “capture_output=True”. You can individually access stdout and stderr values by using “output. stdout” and “output.
The subprocess module defines one class, Popen and a few wrapper functions that use that class. The constructor for Popen takes arguments to set up the new process so the parent can communicate with it via pipes. It provides all of the functionality of the other modules and functions it replaces, and more.
subprocess. check_call() gets the final return value from the script, and 0 generally means "the script completed successfully".
call() when you want the program to wait for the process to complete before moving onto the next process. In the case of subprocess. run() , the program will attempt to run all the processes at once, inevitably causing the program to crash.
The call() function is just Popen(*args, **kwargs).wait(). You could call Popen directly and use stdout=PIPE argument to read from p.stdout:
#!/usr/bin/env python
import sys
from subprocess import Popen, PIPE
from threading import Thread
def tee(infile, *files):
"""Print `infile` to `files` in a separate thread."""
def fanout(infile, *files):
with infile:
for line in iter(infile.readline, b""):
for f in files:
f.write(line)
t = Thread(target=fanout, args=(infile,) + files)
t.daemon = True
t.start()
return t
def teed_call(cmd_args, **kwargs):
stdout, stderr = [kwargs.pop(s, None) for s in ["stdout", "stderr"]]
p = Popen(
cmd_args,
stdout=PIPE if stdout is not None else None,
stderr=PIPE if stderr is not None else None,
**kwargs
)
threads = []
if stdout is not None:
threads.append(
tee(p.stdout, stdout, getattr(sys.stdout, "buffer", sys.stdout))
)
if stderr is not None:
threads.append(
tee(p.stderr, stderr, getattr(sys.stderr, "buffer", sys.stderr))
)
for t in threads:
t.join() # wait for IO completion
return p.wait()
outf, errf = open("out.txt", "wb"), open("err.txt", "wb")
assert not teed_call(["cat", __file__], stdout=None, stderr=errf)
assert not teed_call(["echo", "abc"], stdout=outf, stderr=errf, bufsize=0)
assert teed_call(["gcc", "a b"], close_fds=True, stdout=outf, stderr=errf)
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