1#!/bin/bash
2# cal2day - "parse" appropriate calendar output to match date number
3#	    with day name.
4#
5# usage: cal2day month day [year]
6#
7# ORIGINAL *TAG:33239 3:Dec 9 1997:0755:sh.d/cal2day:
8#
9# Obtained from usenet
10#
11# Converted to bash v2 syntax by Chet Ramey <chet@po.cwru.edu>
12
13#1 PARSE OPTIONS
14while getopts :dls _inst
15do	case $_inst in
16	(d)	format='%1d%.0s\n' ;;		# 0, 1, ..., 7
17	(l)	format='%0.s%-s\n' ;;		# Sunday, Monday, ..., Saturday
18	(s)	format='%0.s%-.3s\n' ;;		# Sun, Mon, ..., Sat
19	esac
20done
21shift $((OPTIND-1))
22
23#2 PARAMETER VALUES
24((!$#)) && set -- $(date '+%m %d')
25: ${format:='%0.s%-.3s\n'}
26: ${1:?missing month parameter [1-12]}
27: ${2:?missing day parameter [1-31]}
28
29#3 CALCULATE DAY-OF-WEEK FROM DATE
30cal $1 ${3:-$(date +%Y)} | gawk -FX '
31BEGIN	{ day="Sunday   Monday   Tuesday  WednesdayThursday Friday   Saturday"
32	  sub(/^0/, "", daynum)
33	  dayre="(^| )" daynum "( |$)"
34	}
35#NR==2	{ print length($0) }
36NR==1 || NR==2 \
37	{ next }
38dayre	{ if (match($0, dayre))
39	  {	#print RSTART, RLENGTH, substr($0, RSTART, RLENGTH)
40		if (daynum<=9 || RSTART==1) RSTART-=1
41		exit
42	  }
43	}
44END	{ # 20/21 char width assumed
45	  printf format, RSTART/3, substr(day, RSTART*3+1, 9)
46	}
47' daynum=$2 format=$format -
48
49exit 0
50