Python issue: commands.getoutput(command) fails

kenneho · 05-26-2010, 03:42 AM

Hi.

I've writte a small Munin plugin using python, which basically runs a shell command, and write the output to a file. For some reason the script fail quite often, and it seems to be failing at the "commands.getoutput" statement. This is what's leading up to that statement:

Code:

varA = someString[0:11] 
command = "/bin/grep \"%s\" /path/to/file.txt|wc -l" % varA 
command_output = commands.getoutput(command)

I've added some debugging statements writing the "command" variable to file, and the doesn't seem to be anything wrong with the command itself. But for some reason things fail. Any ideas on how to debug this?

- kenneho

Sergei Steshenko · 05-26-2010, 04:03 AM

Quote:

Originally Posted by kenneho

Hi.

I've writte a small Munin plugin using python, which basically runs a shell command, and write the output to a file. For some reason the script fail quite often, and it seems to be failing at the "commands.getoutput" statement. This is what's leading up to that statement:

Code:

varA = someString[0:11] 
command = "/bin/grep \"%s\" /path/to/file.txt|wc -l" % varA 
command_output = commands.getoutput(command)

I've added some debugging statements writing the "command" variable to file, and the doesn't seem to be anything wrong with the command itself. But for some reason things fail. Any ideas on how to debug this?

- kenneho

Python does have regular expressions, doesn't it ? So why spawning processes using 'grep', 'wc' in the first place ?

kenneho · 05-26-2010, 06:58 AM

Quote:

Originally Posted by Sergei Steshenko

Python does have regular expressions, doesn't it ? So why spawning processes using 'grep', 'wc' in the first place ?

I didn't know that. This is my first python script, so I'm still learning. I'll check out regexps!

Sergei Steshenko · 05-26-2010, 10:37 AM

Quote:

Originally Posted by kenneho

I didn't know that. This is my first python script, so I'm still learning. I'll check out regexps!

AFAIK, there is a separate module implementing regular expressions. I am not a Python guy, so I can't be more specific off the top of my head.

bgeddy · 05-26-2010, 02:49 PM

Quote:

AFAIK, there is a separate module implementing regular expressions. I am not a Python guy, so I can't be more specific off the top of my head.

Have a look at the re module - it's part of the Python Standard Library.