Generate calendar applet in shell using AWK

Recently, when I was studying sed and awk, I found a good book at the entry level: "Software Design Chinese Version 03".
We also get the calendar program here from where we can get it. We strongly recommend this book for comrades who want to know Sed and AWK.

Code snippet:

# Generate calendar in shell# How to use#  awk -f thisFile +2017
#  awk -f thisFile +2017.10
#  awk -f thisFile +2017.10.10
#
function whichWeek(y, m, d, s) {
    s = 0
    if (((y%4 == 0) &amp;&amp; (y%100 != 0)) || (y%400 == 0)) if (M[2] == 28) M[2]++
    if (y&gt;0) s += --y + int(y/4) - int(y/100) + int(y/400)
    while (m &gt; 1) s += M[--m]
    return (s+d)%7
}

function printCalendar(y, m, d, nowWeek, i){
  printf("%d%s %d%s\n", y, "Year", m, "moon")
  print "Day, two, three, four, five, six"
  printf("%s", repeat(" ", ((nowWeek+1)%7)*3))
  for (i=1; i&lt;=M[m]; i++) {
    if ((nowWeek+i) % 7 != 6) {
      printf("%2d ", i)
    } else {
      printf("%2d \n", i)
    }
  }
  print "\n"
}
function repeat(flag, time, i, str){
  for (i=0; i&lt;time; i++) {
    str = str flag
  }

  return str
}
function option(opt) {
  if (ARGC &gt; 1 &amp;&amp; ARGV[1] ~ /^\+.*$/) {
    print ARGC, ARGV[1]
    opt = substr(ARGV[1], 2)
    delete ARGV[1]
  }
  return opt
}
BEGIN {
  M[1] = 31
  M[2] = 28
  M[3] = 31
  M[4] = 30
  M[5] = 31
  M[6] = 30
  M[7] = 31
  M[8] = 31
  M[9] = 30
  M[10] = 31
  M[11] = 30
  M[12] = 31
  W[0] = "day"
  W[1] = "one"
  W[2] = "two"
  W[3] = "three"
  W[4] = "Four"
  W[5] = "five"
  W[6] = "six"
  split(option(), date, ".")
  nowWeek = whichWeek(date[1]+0, date[2]+0, date[3]+0)
  if (date[3] != "") {
    print "Week" W[nowWeek]
  } else if (date[2] != "") {
    printCalendar(date[1]+0, date[2]+0, M[date[2]], nowWeek)
  } else {
    for (j=1; j&lt;=12; j++) {
      printCalendar(date[1]+0, j, M[i], whichWeek(date[1]+0, j, 0))
    }
  }
}

The above is all the content of this article. I hope it will be helpful to everyone's study and I hope everyone will support me more.