subprocess实时获取结果和捕获错误

需要调用命令行来执行某些命令，主要是用 subprocess 实时获取结果和捕获错误，发现subprocess的很多坑。

subprocess 普通获取结果方式，其需要命令完全执行才能返回结果：

import subprocess
scheduler_order = "df -h"
return_info = subprocess.Popen(scheduler_order, shell=True, stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
for next_line in return_info.stdout:
    return_line = next_line.decode("utf-8", "ignore")
    print(return_line)

客subprocess 实时获取结果：

import subprocess
scheduler_order = "df -h"
return_info = subprocess.Popen(scheduler_order, shell=True, stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
while True:
    next_line = return_info.stdout.readline()
    return_line = next_line.decode("utf-8", "ignore")
    if return_line == '' and return_info.poll() != None:
        break
    print(return_line)

想要获取报错机制，使用 check_output 捕捉报错和使用 check_call 捕捉报错，及时在 Popen 中捕获报错，都会使 实时输出失效 ！，所以自行查看 CalledProcessError 源码终于搞定。

实时发送以及捕获报错：

import subprocess
try:
    scheduler_order = "top -u ybtao"
    return_info = subprocess.Popen(scheduler_order, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    while True:
        next_line = return_info.stdout.readline()
        return_line = next_line.decode("utf-8", "ignore")
        if return_line == '' and return_info.poll() != None:
            break
        print(return_line)
    returncode = return_info.wait()
    if returncode:
        raise subprocess.CalledProcessError(returncode, return_info)
except Exception as e:
    print(e)