带有 sudo python 脚本的 crontab

Question

好的，我找到了一些东西。不知道如何解决它。我已经看到这是 google 中出现的常见错误。该错误似乎与环境变量或其他东西有关。不知道如何处理：

这是代码，它是调用子进程的部分导致错误：

#!/usr/bin/python

import subprocess
import re
import sys
import time
import datetime
import gspread

# ===========================================================================
# Google Account Details
# ===========================================================================

# Account details for google docs
email       = 'my_email@gmail.com'
password    = 'my_password'
spreadsheet = 'my_spreadsheet'

# ===========================================================================
# Example Code
# ===========================================================================


# Login with your Google account
try:
  gc = gspread.login(email, password)
except:
  print "Unable to log in.  Check your email address/password"
  sys.exit()

# Open a worksheet from your spreadsheet using the filename
try:
  worksheet = gc.open(spreadsheet).sheet1
  # Alternatively, open a spreadsheet using the spreadsheet's key
  # worksheet = gc.open_by_key('0BmgG6nO_6dprdS1MN3d3MkdPa142WFRrdnRRUWl1UFE')
except:
  print "Unable to open the spreadsheet.  Check your filename: %s" % spreadsheet
  sys.exit()

# Continuously append data
while(True):
  # Run the DHT program to get the humidity and temperature readings!

  output = subprocess.check_output(["./Adafruit_DHT", "2302", "17"]);
  print output
  matches = re.search("Temp =\s+([0-9.]+)", output)
  if (not matches):
        time.sleep(3)
        continue
  temp1 = float(matches.group(1))
  temp = temp1*9/5+32 # added the extra step to converto to fahrenheit

  # search for humidity printout
  matches = re.search("Hum =\s+([0-9.]+)", output)
  if (not matches):
       time.sleep(3)
       continue
  humidity = float(matches.group(1))

  print "Temperature: %.1f F" % temp
  print "Humidity:    %.1f %%" % humidity

  # Append the data in the spreadsheet, including a timestamp
  try:
    values = [datetime.datetime.now(), temp, humidity]
    worksheet.append_row(values)
  except:
    print "Unable to append data.  Check your connection?"
    sys.exit()

  # Wait 30 seconds before continuing or just exit
  print "Wrote a row to %s" % spreadsheet
#  time.sleep(60)
  sys.exit()

基本上就是这样。只要 Adafruit_DHT 程序位于同一目录中，使用“sudo python script.py”就可以正常工作。

这是我得到的错误：

Traceback (most recent call last):
  File "/home/pi/Adafruit/dht/Ada_temp.py", line 44, in <module>
    output = subprocess.check_output(["./home/pi/Adafruit/dht/Adafruit_DHT", "2302", "17"]);
  File "/usr/lib/python2.7/subprocess.py", line 537, in check_output
    process = Popen(stdout=PIPE, *popenargs, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1259, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

我已经尝试添加c程序的完整路径（Adafruit_DHT），但无济于事......

Answer 1

找出问题所在。

1. 脚本是否运行？ 在脚本的第一行做一些琐碎的事情，看看它实际上是从 cron 执行的（例如：写入 /tmp 中的文件）。

2. 一旦你设法运行它，寻找其他问题。可以设置 Cron 以发送带有脚本输出的邮件。我看到的一件明显的事情是：./Adafruit_DHT，使用了相对路径，这是一个不好的迹象，cron 脚本可能没有在您认为的目录中执行。修复它（= 使用绝对路径）。

Answer 2

试试：

output = subprocess.check_output(["PATH_TO_Adafruit_DHT/Adafruit_DHT", "2302", "17"]);

哦，将您的 cron 行更改为： /usr/bin/python /home/pi/myscript.py