Regex find until word of end of block

Question

I’m analyzing router logs and found a solution to find blocks of text, but now I’m facing a problem that the end of the text block might not be present. I’ll explain.
This is a sample of a stripped log.

POBL026# show run vpn 0
interface ge0/4
  no shutdown
 !
 interface ge0/4.1
  description "TLOC-Extension Custom1"
  ip address 10.31.xxx.1/30
  nat
   respond-to-ping
   log-translations
  !
  tracker     lbo2
  tunnel-interface
   encapsulation ipsec preference 100 weight 33
   color custom1 restrict
   no allow-service bgp
   allow-service dhcp
   allow-service dns
   allow-service icmp
   no allow-service sshd
   no allow-service Netconf
   no allow-service ntp
   no allow-service ospf
   no allow-service stun
   allow-service https
  !
  mtu         1496
  no shutdown
 !
 interface ge0/4.2
  description    "TLOC-Extension biz-internet  "
  ip address 10.31.xxx.5/30
  mtu            1496
  tloc-extension ge0/0
  no shutdown
 !
 ip route 0.0.0.0/0 10.31.xxx.2
 ip route 0.0.0.0/0 84.198.zzz.217
!
POBL026# show run vpn 1

So with this code I’m able to isolate each vpn block

regex_result = re.search("(?s)(shows*runs*vpns*" + str(vpn_nbr) + "s*n)(.*?)(?=" + routername + ")", filecontent)

Then, in each block I searched for the interfaces with this code

   result = re.findall("(?s)(?<=interface )(.*?)(?=!)"", vpn_block)

But this is not OK as I’ve noticed that my interface-block itself can hold this sens before the end. So, I could search until the next "!ninterface", this works fine, but I’m not getting my last block, as there the end is the routername itself.

So I’m looking for a kind of regex that says, everything after the sequence "interface" until "!ninterface" OR "end of the block".

Can this be done?

Asked By: Harry Leboeuf

||

Source

Answer 1

You can use the $ character to specify the end of the string.

 result = re.findall(r"(?s)(?<=interface )(.*?)(?=!ns*interface|$)", vpn_block)

The:

(?=!ns*interface|$)

is a positive lookahead that matches until the next interface or the end of block (|$).

Note that you cannot use $ inside a character class []. Inside [$], $ loses its special meaning and is a literal character to match.

Answered By: Amal K

Regex find until word of end of block

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