Python脚本输出到控制台，即使它在后台运行

I am running a python script in background, but why does it still prints to console, even when piped to a file?

我在后台运行python脚本,但为什么它仍然打印到控制台,即使用管道传输到文件?

I tried the following command:

我尝试了以下命令:

python script.py &
python script.py > output.txt &

I tried with a simple script:

我试过一个简单的脚本:

print "hello world"

With

python script.py &

It still prints to console.

它仍然打印到控制台。

But

python script.py > output.txt &

works as intended and does not print to console.

按预期工作,不打印到控制台。

5 个解决方案

#1

Probably it is outputing on stderr. Try this:

可能它是在stderr上输出的。试试这个:

python script.py > output.txt 2>&1 &

Alternatively it looks like you might have started a background task that is still running:

或者看起来您可能已经启动了仍在运行的后台任务:

python script.py &

Type fg to bring it to the foreground, and then kill it with Ctrl-C.

键入fg将其置于前台,然后使用Ctrl-C将其终止。

#2

Even this is not enough sometimes. Some applications write to /dev/console instead of /dev/stdout or /dev/stderr. Applications that prompt for a password often do this.

即使这有时也不够。某些应用程序写入/ dev / console而不是/ dev / stdout或/ dev / stderr。提示输入密码的应用程序通常会这样做。

#3

Should that have been

应该是这样的

python script.py > output.txt 2>&1 & 
python script.py >> output.txt 2>&1

See this for a clarification on the usage of 2>&1

有关2>&1的用法的说明,请参阅此处

#4

The problem with python here is that it would buffer stdout and won't drop it to disk. You need to run your script like that

这里python的问题是它会缓冲stdout并且不会将它丢弃到磁盘上。你需要像这样运行你的脚本

python -u script.py > output.txt &

Or you can use unbuffered output (unbuffered stdout in python (as in python -u) from within the program)

或者您可以在程序中使用无缓冲的输出(python中的无缓冲的stdout(如在python -u中))

#5

Do you print to standard output or standard error? those are two different streams.

您是否打印到标准输出或标准错误?这是两个不同的流。

Program 2> file # pipe standard error
Program 2>&1 # pipe standard error to standard output (join streams)
Program > file 2>&1 # pipe both channels to file

#1