问题描述
这是我在python中运行并获得预期结果的bash命令:
This is a bash command that I run in python and get the expected result:
count = subprocess.Popen("ps -ef | grep app | wc -l", stdout=subprocess.PIPE, shell=True)
但是当我想传递一个参数(在这种情况下为count)时，我不知道该怎么做.我试过了:
but when I'd like to pass an argument (count in this case) cannot figure out how to do it.I tried:
pid = subprocess.call("ps -ef | grep app | awk -v n=' + str(count), 'NR==n | awk \'{print $2}\'", shell=True)
和
args = shlex.split('ps -ef | grep app | awk -v n=' + str(count), 'NR==n | awk \'{print $2}\'')
pid = subprocess.Popen(args, stdout=subprocess.PIPE, shell=True)
在这里的各种帖子中，还有其他尝试，但仍然无法实现.
among other attempts, from various posts here, but still cannot make it.
推荐答案
您正在混合使用引号和结束语，并且在其他尝试中误将冒号传递了.
You're mixing opening and closing quotations and you pass a colon by mistake on your other attempts among other things.
请尝试以下解决方法:
pid = subprocess.call("ps -ef | grep app | awk -v n=" + str(count) + " NR==n | awk '{print $2}'", shell=True)
您使用"打开了命令参数，因此在使用" 和 + str()进行操作之前，需要先将其关闭不是'.此外，我将，'NR = 换为 +"NR = ，因为您想向命令添加更多内容，而不是将参数传递给 subprocess.call().
You opened the command parameter with " and there for you need to close it before you do + str() with a " and not a '. Further more i swapped the , 'NR= with + "NR= since you want to append more to your command and not pass a argument to subprocess.call().
正如评论中指出的那样，用 shlex 拆分命令毫无意义，因为管道命令未在 subprocess 中实现，但是我想指出通常不建议使用 shell = True ，因为例如.
As pointed out in the comments, there's no point in splitting the command with shlex since piping commands isn't implemented in subprocess, I would however like to point out that using shell=True is usually not recommended because for instance one of the examples given here.
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