如何在顺序重要的地方在python脚本中运行多个linux命令

Question

I'm trying to execute several linux commands sequentially in my python script using subprocess.Popen(). However, it seems like the way I'm writing the script, python is doing some sort of execute and forget and not waiting for step 1 to finish before starting step 2.

Case in point, I'm trying to:

1. Execute a SQL command, which writes the results to a file in /tmp on the remote server.
2. After I'm finished using the file, I want to delete the remote file, so we don't run out of space.

What's happening is python seems to run the cmd for step 1 and without waiting for step 1 to complete, it runs step 2. So the file is still hanging around since the delete is run before the file is created.

Here's my code snippet. Hopefully someone can tell me how to make it so step 2 only runs after step 1 has completed. I tried to anonymize/simplify the snippet so pls excuse any mistakes made while anonymizing the code.

   sqlCmd = "ssh " + HOST + "mysql -h host -ppwd -q select blah from table where foo = 'bar' INTO OUTFILE '/tmp/blah_bydate.csv"
   rmCmd = "ssh " + HOST + " rm -f /tmp/blah_bydate.csv"
   proc = subprocess.Popen(sqlCmd, shell=True, stdout=subprocess.PIPE)
   proc = subprocess.Popen(rmCmd, shell=True, stdout=subprocess.PIPE)

I found something on SO where the suggested solution was to do something like

subprocess.Popen([cmd1; cmd2; cmd3], shell=True, stdout=subprocess.PIPE)

which I don't want to do since my commands are parametrized and can be long/complex.

Answer 1

只需使用subprocess.call而不是subprocess.Popen ，它就应该阻塞直到进程完成。

Answer 2

您可以使用proc.wait（），如果需要的话甚至可以使用超时值。