Grep Regular-Expressions on more lines

Dear all, I am writing a python program that is retrieving edifact log messages from a .gz file... An example of 2 logs are the following:

2009/03/02 12:13:59.642396 siamp102 mux1-30706 Trace name: MSG
Message sent [con=251575 (APEOBEinMux1), len=2106, CorrID=000182C42DE0ED]
UNB+IATB:1+1ASRPFA+1A0APE+090302:1213+0095JQOL2

2009/03/02 12:14:00.029496 siamp102 mux1-30706 Trace name: MSG
Message sent [con=737 (APIV2_1), len=22370, CorrID=000182C42DE0ED]
UNB+IATB:1+1ASIFQLFS+1ARIOFS+090302:1214+0122V11ON9

I would like to write a regular expression able to match some field from the first line, some from the second and some other from the third ...

Is there any way to write a regular expression to be used with GREP that matches field from consecutive lines ??

Thanks in advance !!!

From stackoverflow

• With grep alone, I think this is not possible. I would suggest awk or perl in order to be able to save some context from previous lines.

  In perl this gives something like:

  #!/usr/bin/env perl
  
  $isInLogSection = 'NO';
  while (<>) {
      if ( /siamp102/ ) {
          # Start of log section: retrieve its ID
          $isInLogSection = 'YES';
          split;
          $logSectionID = $_[0];
      }
  
      if ($isInLogSection eq YES && /len=/) {
          # Retrieve value of len
          ...
      }
  
      if ( /^$/ ) {
          # End of log section
          $isInLogSection = 'NO';
      }
  }
  

  In awk this gives something like:

  BEGIN { isInLogSection = "NO"; }
  /siamp102/ { isInLogSection = "YES"; logSectionID = $1; }
  /len=/ { if (isInLogSection == "YES") { #retrieve len value } }
  /^$/ { isInLogSection = "NO" }
  

  I am not 100% certain of the exact syntax. This is mainly a canvas for illustrating the principles.

  IceMan85 : Can u please suggest me the syntax for the awk command able to select some element form first, second and third line ? Thanks

  mouviciel : Oops sorry, when you added your comment I was editing my answer with a perl example...

  mouviciel : awk version added.