How to send a subprocess to the background & without using shell=True
I'm trying to write a part of a Python script what changes the root MySQL password under Linux for a small web-admin interface. I've followed the official MySQL documentation on changing the root password, and came up with this shell script, what works nicely:
shopt -s xpg_echo # stopping running MySQL server invoke-rc.d mysql stop # creating init file in a mysqld readable location cat > /var/lib/mysql/mysql-init <<END UPDATE mysql.user SET Password=PASSWORD('x123') WHERE User='root'; FLUSH PRIVILEGES; END # running mysqld_safe with init-file in the background mysqld_safe --init-file=/var/lib/mysql/mysql-init & sleep 5 # stopping mysql invoke-rc.d mysql stop # deleting the init file rm /var/lib/mysql/mysql-init # starting mysql invoke-rc.d mysql start
There is one part, where I have to start mysqld_safe and let it run for a few seconds and the stop it nicely with invoke-rc.d. In the shell script I could solve it with & and sleep 5.
My problem is that I don't know how could I do this in the Python script without using shell=True. I could do all the other parts with Popen and shlex.split(cmd), but & doesn't seem to go through either shlex.split(cmd) or through shell=False.
Is it just a simple problem with & in the command line or I really need shell=True for this? If not, do I need to use threads?
& is a shell thing, so, yes, if you want to use & to run a command in the background, you need the shell. However, you can also do this entirely in Python:
proc = subprocess.Popen(["mysqld_safe", "--init-file=/var/lib/mysql/mysql-init"]) time.sleep(5) proc.kill()
I'm probably missing something, but wouldn't something like this work?
import time import subprocess p = subprocess.Popen(['mysqld_safe', '--init-file=/var/lib/mysql/mysql-init']) time.sleep(5) subprocess.call(['invoke-rc.d', 'mysql', 'stop'])