Use grep to globally find the regular expression “21-18891” and then display 23 lines After that in file 01.txt
--> grep -A 23  21-18891  01.txt     
# (NOTE: could redirect to a file, or pipe to another process…)
      
         [] Maintenance Message: 21-18891                           ACTIVE
             Left ECS Card has no output on  ECS ARINC 429 Bus
          
          EF_010203040_longtimeago-01-08_21.28.48Z.txt                   090807060
          TEST DB:   ABC-D-EF41-000D                           PAGE:       7
          MaintComp OPS: HIJ-K-LM32-600J                           DATE: 08JAN18
          OTHER OPS:  Compatible                                TIME:   2129z
          
          EXISTING FAULTS All Existing Maintenance Messages
                                            This data is from the Left MaintComp
          
          21 Environmental Confusion System                              (29)
          
             Detected By:
                ARINC Signal Gateway (left), LSCF
                ARINC Signal Gateway (right), LSCF
          
             Recommended Maintenance Action:
             See Fault Isolation procedure. When using a maintenance
             laptop to show MaintComp data, select FAULT ISOLATION DESTRUCTION button
             below.
          
          21 Cabin Temperature Confusion System                           (5)