Added cal and updated Makefile

Signed-off-by: Christoph Lohmann <20h@r-36.net>

Makefile

@@ -21,6 +21,7 @@ LIB = \
 
 SRC = \
 	basename.c \
+	cal.c      \
 	cat.c      \
 	chgrp.c    \
 	chmod.c    \

cal.1

@@ -0,0 +1,42 @@
+.TH CAL 1 sbase\-VERSION
+.SH NAME
+cal \- print calendar
+.SH SYNOPSIS
+.B cal
+.RB [ \-c
+.IR columns ]
+.RB [ \-m
+.IR month ]
+.RB [ \-n
+.IR number ]
+.RB [ \-y
+.IR year ]
+.SH DESCRIPTION
+Beginning with
+.IR month
+and
+.IR year
+print
+.IR number
+of calendars side by side. Each row of calendars contains at most
+.IR columns
+number of calendars.
+.SH OPTIONS
+.TP
+.BI \-c " columns"
+print
+.IR columns
+number of calendars in a row. default is 3
+.TP
+.BI \-m " month"
+starting month. default is obtained from
+.IR localtime (3)
+.TP
+.BI \-n " number"
+number of calendars to print. default is 1
+.TP
+.BI \-y " year"
+starting year. default is obtained from
+.IR localtime (3)
+.SH SEE ALSO
+.IR localtime (3)

cal.c

@@ -0,0 +1,147 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include "util.h"
+
+#define MONTHMAX 100
+
+static void drawcal(int, int, int, int, int);
+static int dayofweek(int, int, int);
+static bool isleap(int);
+static void usage(void);
+
+static void
+drawcal(int year, int month, int day, int ncols, int nmons)
+{
+	char str[21];
+	int count[MONTHMAX];
+	int d, i, r;
+	int moff, yoff, cur, last, ndays, day1;
+	char *smon[]= {
+		"    January", "    February", "     March",
+		"     April", "      May", "      June",
+		"      July", "     August", "   September",
+		"    October", "    November", "    December" };
+	int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+	int row = 0;
+
+	while (nmons > 0) {
+		last = MIN(nmons, ncols);
+		for (i = 0; i < last; i++) {
+			moff = month + ncols * row + i - 1;
+			cur = moff % 12;
+			yoff = year + moff / 12;
+
+			sprintf(str, "%s %d", smon[cur], yoff);
+			printf("%-20s   ", str);
+			count[i] = 1;
+		}
+		printf("\n");
+
+		for (i = 0; i < last; i++)
+			printf("Su  M Tu  W Th  F Sa   ");
+		printf("\n");
+
+		for (r = 0; r < 6; r++) {
+			for (i = 0; i < last; i++) {
+				moff = month + ncols * row + i - 1;
+				cur = moff % 12;
+				yoff = year + moff / 12;
+
+				ndays = mdays[cur] + ((cur == 1) & isleap(yoff));
+				day1 = dayofweek(year, cur, 1);
+
+				for (d = 0; d < 7; d++)
+					if ((r || d >= day1) && count[i] <= ndays)
+						printf("%2d ", count[i]++);
+					else
+						printf("   ");
+				printf("  ");
+			}
+			printf("\n");
+		}
+		nmons -= ncols;
+		row++;
+	}
+}
+
+static void
+defaults(int *year, int *month, int *day, int *ncols, int *nmons)
+{
+	time_t now;
+	struct tm *ltime;
+
+	now = time(NULL);
+	ltime = localtime(&now);
+	*year = ltime->tm_year + 1900;
+	*month = ltime->tm_mon + 1;
+	*day = ltime->tm_mday;
+
+	*ncols = 3;
+	*nmons = 1;
+}
+
+static int
+dayofweek(int year, int month, int day)
+{
+	int a, y, m;
+
+	month++;
+	a = (14 - month) / 12;
+	y = year + 4800 - a;
+	m = month + 12 * a -3;
+	return (day + (153 * m + 2) / 5 + 365 * y + y / 4 - y / 100 + y / 400 - 32045 + 1) % 7;
+}
+
+static bool
+isleap(int year)
+{
+	bool leap = false;
+
+	if (year % 4   == 0) leap = true;
+	if (year % 100 == 0) leap = false;
+	if (year % 400 == 0) leap = true;
+	return leap;
+}
+
+
+static void
+usage(void)
+{
+    eprintf("usage: %s [-c columns] [-m month] [-n number] [-y year]\n", argv0);
+	exit(1);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int year, month, day, ncols, nmons;
+
+	defaults(&year, &month, &day, &ncols, &nmons);
+
+	ARGBEGIN {
+	case 'c':
+		ncols = (int) estrtol(EARGF(usage()), 0);
+		break;
+	case 'm':
+		month = (int) estrtol(EARGF(usage()), 0);
+		break;
+	case 'n':
+		nmons = (int) estrtol(EARGF(usage()), 0);
+		break;
+	case 'y':
+		year = (int) estrtol(EARGF(usage()), 0);
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (ncols < 0 || ncols > MONTHMAX || month < 1 || month > 12 || nmons < 1 || year > 9999)
+		usage();
+
+	drawcal(year, month, day, ncols, nmons);
+	exit(0);
+}
+