Question

For the first time, I am asking a little bit of help over here as I am more of a ServerFault person.

I am doing some scripting in Python and I’ve been loving the language so far yet I have this little problem which is keeping my script from working.

Here is the code line in question :

subprocess.call('xen-create-image --hostname '+nom+' --memory '+memory+' --partitions=/root/scripts/part.tmp --ip '+ip+' --netmask '+netmask+' --gateway '+gateway+' --passwd',shell=True)

I have tried the same thing with os.popen. All the variables are correctly set.

When I execute the command in question in my regular Linux shell, it works perfectly fine but when I execute it using my Python scripts, I get bizarre errors. I even replaced subprocess.call() by the print function to make sure I am using the exact output of the command.

I went looking into environment variables of my shell but they are pretty much the same… I’ll post the error I am getting but I’m not sure it’s relevant to my problem.

Use of uninitialized value $lines[0] in substitution (s///) at /usr/share/perl5/Config/IniFiles.pm line 614.
Use of uninitialized value $_ in pattern match (m//) at /usr/share/perl5/Config/IniFiles.pm line 628.

I am not a Python expert so I’m most likely missing something here.

Thank you in advance for your help,

Antoine

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EDIT

Following miax’s advice, I stopped using shell=True. Instead I took a look at the Python documentation for subprocess and used the following piece of code :

cmd = 'xen-create-image --hostname '+nom+' --memory '+memory+' --partitions=/root/scripts/part.tmp --ip '+ip+' --netmask '+netmask+' --gateway '+gateway+' --passwd'
args = shlex.split(cmd)
subprocess.call(args)

Sadly, it doesn’t change anything…

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EDIT2

I have used the tip given by miax but I still get the above error… Here is the code that I have used.

cmd = ['xen-create-image', '--hostname', nom, '--memory', memory, '--partitions=/root/scripts/part.tmp', '--ip', ip, '--netmask', netmask, '--gateway', gateway, '--passwd']
subprocess.call(cmd)

This is really strange… The exact command works fine when I run it in the regular shell…

Answer 1

Does the xen-create-image script start with a hashbang? That is, is the first line something like

#!/bin/sh

? That is one thing to check. Another is that you can try to call your command as:

cmd = ['/bin/sh', '-c', 'xen-create-image --hostname %s --memory %s --partitions=/root/scripts/part.tmp --ip %s --netmask %s --gateway %s --passwd' % (nom, memory, ip, netmask, gateway)]
subprocess.call(cmd, shell=False)

You might want to print cmd to verify this is the command you intend to run (i.e. check the substitutions).