Calculating Running Average with AWK

avg.awk

BEGIN {
  avg = 0.0
  sigma = 0.0
}

{
  v = $1
  avg = (avg*(NR - 1) + v) / NR
  sigma = (sigma*(NR - 1) + v*v) / NR
}

END {
  printf("Avg: %.2f, sigma: %.2f, total %.2f with %d records\n",
      avg, sqrt(sigma - avg*avg), avg*NR, NR)
}