Pattern mapping

Shell Programming and Scripting
1

Dear Friends,

Please help me on this
I have file A.txt containing text lines as below

grectec; 30 ,50, 60, base_123 ; top09
grectec; 30 ,55, 60, base_123 ; top09  
grectec; 10 ,53, 60, base_123 ; top09
grectec; 50 ,57, 60, base_123 ; top09
...
...

another file B.txt containing test lines as below

10 ken
30 jack
50 sack
60 mug

I need a script that check if the line containing text 30 add ken at the end of the line, similarly if the line containing 10 add ken at the end of the line.

output should be as: C.txt

grectec; 30 ,50, 60, base_123 ; top09 jack
grectec; 30 ,55, 60, base_123 ; top09 jack
grectec; 10 ,53, 60, base_123 ; top09 ken
grectec; 50 ,57, 60, base_123 ; top09 sack

I think its would be done using join command but dont know how:

2 
awk > C.txt 'NR == FNR {
  b[$1] = $2; next
  }
$0 = $0 FS b[$2]
  ' B.txt A.txt
3

Below code works exactly as you want.but a.txt should be like
A.txt.

grectec; 10 ,53, 60, base_123 ; top09
grectec; 30 ,50, 60, base_123 ; top09
grectec; 30 ,55, 60, base_123 ; top09
grectec; 50 ,57, 60, base_123 ; top09

 
join -j1 2 -j2 1 a.txt b.txt
4

Thanks Radoulov,

It worked, i need a little more help:

File a.txt 
1    1     bash    enable   unlocked
1    4     kash    enable   locked
1    8     gash    enable   unlocked
2    1     bash    enable   unlocked
2    3     Lash    enable   unlocked 
2    7     Pash    enable   unlocked

another File b.txt

1    1     jack
1    2     yack
1    4     back
1    8     sack
2    1     pack
2    3     fack
2    4     mack
2    7     lack

i need a third file c.txt on a mapping criteria of first two columns

1 1 jack bash enable unlocked
1 4 back kash enable locked
1 8 sack gash enable unlocked
2 1 pack bash enable unlocked
2 3 fack Lash enable unlocked
2 7 lack Pash enable unlocked

5 
awk 'NR == FNR {
  key[$1, $2] = $3; next
  }
$2 = $2 OFS key[$1, $2]
  ' OFS=\\t b.txt a.txt