Python 子进程异常

Question

我正在将subprocess.check_output命令用于两个不同的命令，在一种情况下，我得到了一个子进程。调用进程错误，在另一种情况下不是，但程序崩溃。gpio482 文件夹不存在，set 方法返回错误，get 方法崩溃

获取捕获异常的方法：

try:
    subprocess.check_output("echo 0 > /sys/class/gpio/gpio482/value", shell=True)
except subprocess.CalledProcessError:
    log("set state failed.")
    return "not-writable"

获取崩溃的方法：

    try:
    state_string = subprocess.check_output("cat /sys/class/gpio/gpio482/value", shell=True)
except subprocess.CalledProcessError:
    log("Get state failed.")
    return "integer", "0" # unknown

我做错了什么吗？！

如果我在 shell 中运行公共资源，我会收到相同的错误消息：

>>> subprocess.check_output("cat /sys/class/gpio/gpio482/value", shell=True)
cat: can't open '/sys/class/gpio/gpio482/value': No such file or directory
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/subprocess.py", line 573, in check_output
raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command 'cat /sys/class/gpio/gpio482/value' 
returned non-zero exit status 1
>>> 
>>> 
>>> subprocess.check_output("echo 0 > /sys/class/gpio/gpio482/value", 
shell=True)
/bin/sh: /sys/class/gpio/gpio482/value: No such file or directory
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/subprocess.py", line 573, in check_output
raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command 'echo 0 > 
/sys/class/gpio/gpio482/value' returned non-zero exit status 1

Answer 1

这两个函数如下所示。set函数工作正常，我捕获了异常，但在get函数中我崩溃了。

def get_uid_light_state():
log("get_uid_light_state")
try:
    state_string = subprocess.check_output("cat /sys/class/gpio/gpio482/value", shell=True)
except subprocess.CalledProcessError:
    log("Get state failed.")
    return "integer", "0" 
if state_string == "1n":
    return "integer", "2" 
elif state_string == "0n":
    return "integer", "1" 
def set_uid_light_state(snmptype, state):
if snmptype != "integer":
    return "wrong-type"
if state == "1": 
    cmd_set_state = "echo 0 > /sys/class/gpio/gpio482/value"
elif state == "2":
    cmd_set_state = "echo 1 > /sys/class/gpio/gpio482/value"
else:
    log("Invalid value for set uid light state")
    return "wrong-value"
try:
    subprocess.check_output(cmd_set_state, shell=True)
except subprocess.CalledProcessError:
    log("Set state failed.")
    return "not-writable"
return "DONE"