I need help on : how to compare two

[bholav]

I need help on : how to compare two different fields on two differnt lines ,for example in the file below,

. . . . . . . . . . . . 1 . 1 1 1 . . . . . . . . . . . .
. . . . . . . . . . . 1 1 . 1 1 . 1 . . . . . . . . . . .
. . . . . . . . 1 1 . 1 1 . 1 1 . 1 1 1 . . . . . . . . .
2 7 9 9 2 3 2 2 2
2 9 9 9 1 1 1 1 2
1 1 9 2 1 1 1 1 1 1 3 2

I need to compare field 13 on line 1 (which is "1" with field 1 of line 4 (which is a "2" and drop the result back in field 13 of line 1.

I find this forum very informative.Thanks

 

[CaKiwi]

Assuming that all the fields are one character long and you only need to do the replacement once in the file, this script will do what you want. Otherwise you could use split() to isolate field 13 for replacement.

{
  a[NR] = $0
}
END { a[1] = substr(a[1],1,24) substr(a[4],1,1) substr(a[1],26)
      for (i=1;i<=4;i++) print a[i]
}

Hope this helps. CaKiwi