使用 cron 启动 python 脚本并将打印输出到文件 [英] Start python script with cron and output print to a file

问题描述

我正在使用 cron 启动一个 python 脚本，如下所示:

I'm starting a python script using cron, like this:

#Python script called every 3 minutes in case script crashes
*/3 * * * * /home/ubuntu/python_script.sh &

我的脚本有几个用于调试的打印件.我想将这些消息打印到一个文件中，例如/home/ubuntu/Logs.txt

And my script has several prints for debugging. I want to print those messages into a file, for example /home/ubuntu/Logs.txt

我的脚本还会检查 python 调用是否已经在运行，因此它不会再次启动它:

My script also check if the python call is already running so it won't start it again:

#!/bin/bash
lines=$(ps -ef | grep python_script.py | wc -l)

if [ $lines -ne 2 ]; then
    python python_script.py &
fi

如何将我的消息打印到此文件中?我正在使用 python 2.7

How do I print my messages to this file? I'm using python 2.7

更新:使用以下内容编辑我的代码:

Update: Edited my code with the following:

1) 将此添加为我的 python 脚本的第一行:

1) Added this as the first line of my python script:

from __future__ import print_function

2) 在上次导入后打开日志文件，然后添加测试打印:

2) Opened the log file after the last import, and right after that added a test print:

log = open("/home/ubuntu/Logs.txt", "w+")
print("Testing...", file = log)

如果我简单地从终端运行它，它会很好地打印到文件中.但是如果我用 cron 安排它，它就不会写入文件.

If I simple run it from the terminal, it prints to the file fine. But if I schedule it with cron it doesn't write to the file.

更新 2:最终在使用记录器"命令的解决方案上磕磕绊绊.在我的 shell 脚本中，我必须添加2>&1"(在 shell 脚本中，而不是 ElmoVanKielmo 描述的 crontab)和| logger &".最终解决方案如下所示:

Update 2: Ended up stumbling on a solution with "logger" command. On my shell script I had to add "2>&1" (in the shell script, not crontab as described by ElmoVanKielmo) and " | logger &". Final solution looks like this:

#!/bin/bash
lines=$(ps -ef | grep python_script.py | wc -l)

if [ $lines -ne 2 ]; then
    python python_script.py 2>&1 | logger &
fi

并将任何打印输出到/var/log/syslog 文件，这对我来说已经足够了.

and it outputs any prints to /var/log/syslog file, which is good enough for me.

推荐答案

在你的 crontab 中输入:

In your crontab put this:

*/3 * * * * /home/ubuntu/my_script.sh >> /home/ubuntu/Logs.txt

它会将标准输出重定向到这个文件.
您可能还希望重定向 stderr(异常等)，因此:

It will redirect stdout to this file.
You might also want to have stderr redirected (exceptions etc.), so:

*/3 * * * * /home/ubuntu/my_script.sh >> /home/ubuntu/Logs.txt 2>> /home/ubuntu/errors.txt

或者您可以将它们全部放在一个文件中:

Or you can have them all in one file:

*/3 * * * * /home/ubuntu/my_script.sh >> /home/ubuntu/Logs.txt 2>&1

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