Question

我一直在尝试在子进程周围实现一个包装器，如下所示：

def ans_cmd_stream_color(inputcmd):
"""Driver function for local ansible commands.

Stream stdout to stdout and log file with color.
Runs <inputcmd> via subprocess.
Returns return code, stdout, stderr as dict.
"""
fullcmd = inputcmd
create_debug('Enabling colorful ansible output.', LOGGER)
create_info('Running command: ' + fullcmd, LOGGER, True)
p = subprocess.Popen('export ANSIBLE_FORCE_COLOR=true; ' + fullcmd,
                     stdout=subprocess.PIPE,
                     stderr=subprocess.PIPE,
                     shell=True)
stdout_l = []
stderr_l = []
rcode = 0
# Regex black magic
ansi_escape = re.compile(r'\x1b[^m]*m')
# Get the unbuffered IO action going.
try:
    # Non blocking
    reads = [p.stdout.fileno(), p.stderr.fileno()]
    ret = select.select(reads, [], [])
    # Print line by line
    while True:
        for fd in ret[0]:
            if fd == p.stdout.fileno():
                line = p.stdout.readline()
                sys.stdout.write(line.encode('utf-8'))
                stdout_l.append(ansi_escape.sub('',
                                                line.encode('utf-8'))
                                )
            if fd == p.stderr.fileno():
                line = p.stdout.readline()
                sys.stderr.write(line.encode('utf-8'))
                stderr_l.append(ansi_escape.sub('',
                                                line.encode('utf-8'))
                                )
        # Break when the process is done.
        if p.poll() is not None:
            rcode = p.returncode
            break
except BaseException as e:
    raise e
outstr = ''.join(stdout_l)
errstr = ''.join(stderr_l)
outstr, errstr = str(outstr).rstrip('\n'), str(errstr).rstrip('\n')
expstr = errstr.strip('ERROR: ')
if len(expstr) >= 1:
    create_info('Command: ' + str(fullcmd) + ': ' + expstr + '\n', LOGGER,
                True)
    if rcode == 0:
        rcode = 1
else:
    create_info(outstr + '\n', LOGGER)
    if rcode == 0:
        create_info('Command: ' + fullcmd + ' ran successfully.', LOGGER,
                    True)
    expstr = False
ret_dict = {inputcmd: {}}
ret_dict[inputcmd]['rcode'] = rcode
ret_dict[inputcmd]['stdout'] = outstr
ret_dict[inputcmd]['stderr'] = expstr
return copy.deepcopy(ret_dict)

这个想法是打印subprocess命令的流输出，然后将信息返回给函数用户。问题是即使使用直接的io.open，子进程PIP仍然是缓冲的，除非我设置：

os.environ["PYTHONUNBUFFERED"] = "1"

哪个不理想。任何想法或有没有人遇到过这个问题？

更新：使用ansible，您需要为子进程禁用缓冲以兑现缓冲设置：

def ans_cmd_stream_color(inputcmd):
"""Driver function for local ansible commands.

Stream stdout to stdout and log file with color.
Runs <inputcmd> via subprocess.
Returns return code, stdout, stderr as dict.
"""
fullcmd = inputcmd
create_debug('Enabling colorful ansible output.', LOGGER)
create_info('Running command: ' + fullcmd, LOGGER, True)
p = subprocess.Popen('export ANSIBLE_FORCE_COLOR=true; ' +
                     'export PYTHONUNBUFFERED=1; ' + fullcmd,
                     stdout=subprocess.PIPE,
                     stderr=subprocess.PIPE,
                     shell=True)
stdout_l = []
stderr_l = []
rcode = 0
# Regex black magic
ansi_escape = re.compile(r'\x1b[^m]*m')
# Get the unbuffered IO action going.
try:
    # Non blocking
    reads = [p.stdout.fileno(), p.stderr.fileno()]
    ret = select.select(reads, [], [])
    # Print line by line
    while True:
        for fd in ret[0]:
            if fd == p.stdout.fileno():
                line = p.stdout.readline()
                sys.stdout.write(line.encode('utf-8'))
                stdout_l.append(ansi_escape.sub('',
                                                line.encode('utf-8'))
                                )
            if fd == p.stderr.fileno():
                line = p.stdout.readline()
                sys.stderr.write(line.encode('utf-8'))
                stderr_l.append(ansi_escape.sub('',
                                                line.encode('utf-8'))
                                )
        # Break when the process is done.
        if p.poll() is not None:
            rcode = p.returncode
            break
except BaseException as e:
    raise e
outstr = ''.join(stdout_l)
errstr = ''.join(stderr_l)
outstr, errstr = str(outstr).rstrip('\n'), str(errstr).rstrip('\n')
expstr = errstr.strip('ERROR: ')
if len(expstr) >= 1:
    create_info('Command: ' + str(fullcmd) + ': ' + expstr + '\n', LOGGER,
                True)
    if rcode == 0:
        rcode = 1
else:
    create_info(outstr + '\n', LOGGER)
    if rcode == 0:
        create_info('Command: ' + fullcmd + ' ran successfully.', LOGGER,
                    True)
    expstr = False
ret_dict = {inputcmd: {}}
ret_dict[inputcmd]['rcode'] = rcode
ret_dict[inputcmd]['stdout'] = outstr
ret_dict[inputcmd]['stderr'] = expstr
return copy.deepcopy(ret_dict)

Answer 1

您应该直接从子流程管道中读取。以下内容将从标准输出读取到信息记录器，并将标准错误读取到错误记录器。

import logging, subprocess
logging.basicConfig(level=logging.INFO)
proc = subprocess.Popen(
        cmd, stdout=subprocess.PIPE,
        stderr=subprocess.PIPE
    )
cont = True
while cont:
    cont = False
    line = proc.stdout.readline()
    if not line == b"":
        out = line.decode("utf-8").rstrip()
        logging.info(out)
        cont = True

    line = proc.stderr.readline()
    if not line == b"":
        out = line.decode("utf-8").rstrip()
        logging.error(out)
        cont = True

    if not cont and proc.poll() is not None:
        break

要解决缓冲问题，根据this question，从属Python脚本必须显式刷新缓冲区，否则环境变量PYTHONUNBUFFERED必须设置为非空字符串。

无缓冲的Python子进程PIPE

1 个答案: