[Tutor] regular expression

arbaro arbaro arbaro at gmail.com
Thu Aug 3 19:28:42 CEST 2006


I'm trying to mount an usb device from python under linux.
To do so, I read the kernel log /proc/kmsg and watch for something like:
  "<6> /dev/scsi/host3/bus0/target0/lun0/:<7>usb-storage: device scan

When I compile a regular expression like:
  "r = re.compile('<\d+>\s/dev/scsi/host\d+/bus\d+/target\d+/lun\d+')"
It is found. But I don't want the <\d+>\s or '<6> ' in front of the path, so
I tried:
   "r = re.compile('/dev/scsi/host\d+/bus\d+/target\d+/lun\d+')"
But this way the usb device path it is not found.

So what i'm trying to do is:
- find the usb device path from the kernel log with the regular expression.
- Determine the start and end positions of the match (and add /disc or
/part1 to the match).
- And use that to mount the usb stick on /mnt/usb -> mount -t auto match

If anyone can see what i'm doing wrong, please tell me, because I don't
understand it anymore.

Below is the code:

# \d+ = 1 or more digits
# \s  = an empty space

import re

def findusbdevice():
    ''' Returns path of usb device '''
    # I did a 'cat /proc/kmsg /log/kmsg' to be able to read the kernel
    # Somehow I can't read /proc/kmsg directly.
    kmsg = open('/log/kmsg', 'r')
    r = re.compile('/dev/scsi/host\d+/bus\d+/target\d+/lun\d+')
    #r = re.compile('<\d+>\s/dev/scsi/host\d+/bus\d+/target\d+/lun\d+')
    for line in kmsg:
        if 'usb-storage' in line and r.match(line):
            print 'Success', line
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