UNIX for Dummies Questions & Answers

a 1
b 1
c 1
d 2
e 2
f 2

a 2
b 1
c 1
d 1
e 2
f 2

function genrand(n)
{
   return (int(n*rand())+1);
}

BEGIN {
   srand()
}
{ if (!($2 in vA)) {vA[$2]; v[++vN]=$2}
  a[FNR]=$1
}
END {
  for(i=1; i in a;i++)
    print a[i], v[int(genrand(vN))]
}

awk -f fadista.awk myInputFile
OR
for the 9-th column
awk -v c=9 -f fadista.awk myInputFile

function genrand(n)
{
   return (int(n*rand())+1);
}

BEGIN {
   if (!c) c=2;
   srand()
}
{ if (!($c in vA)) {vA[$c]; v[++vN]=$c}
  a[FNR]=$0
}
END {
  for(i=1; i in a;i++) {
    n=split(a[i], A)
    for(j=1;j<=n;j++)
       printf("%s%c", (j==c)? v[int(genrand(vN))]:A[j], (j==n)?ORS:OFS)
  }
}