Question

I am running an msi installer in silent mode and caching logs in the specific file. The following is the command i need to execute.

C:\Program Files\ My Installer\Setup.exe /s /v '/qn /lv %TEMP%\log_silent.log'

I used:

subprocess.Popen(['C:\Program Files\ My Installer\Setup.exe', '/s /v '/qn /lv %TEMP%\log_silent.log''],stdout=subprocess.PIPE).communicate()[0] 

to execute the command however it does not recognise the operation and gives error regarding wrong option selected. I have cross-verified and found that the command only works this way.

Answer 1

The problem is very subtle.

You’re executing the program directly. It gets:

argv[0] = 'C:\Program Files\ My Installer\Setup.exe' argv[1] = /s /v '/qn /lv %TEMP%\log_silent.log' 

Whereas it should be:

argv[1] = '/s' argv[2] = '/v' argv[3] = '/qn' argv[4] = '/lv %TEMP%\log_silent.log' 

In other words, it should receive 5 arguments, not 2 arguments.

Also, %TEMP% is directly unknown to the program!

There are 2 ways to fix this problem:

1. Calling the shell.

   p = subprocess.Popen('C:\Program Files\ My Installer\Setup.exe /s /v '/qn /lv %TEMP%\log_silent.log'', shell=True) output = p.communicate()[0] 

2. Directly call program (more safer)

   s = ['C:\Program Files\ My Installer\Setup.exe', '/s /v '/qn /lv %TEMP%\log_silent.log''] safes = [os.path.expandvars(p) for p in argument_string] p = subprocess.Popen(safes[0], safes[1:]) output = p.communicate()[0]