add cal

apps/cal.c

@@ -0,0 +1,112 @@
+/* vim: tabstop=4 shiftwidth=4 noexpandtab
+ * This file is part of ToaruOS and is released under the terms
+ * of the NCSA / University of Illinois License - see LICENSE.md
+ * Copyright (C) 2019 K. Lange
+ *
+ * cal - print a calendar
+ */
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/time.h>
+
+const char * month_names[] = {
+	"January",
+	"February",
+	"March",
+	"April",
+	"May",
+	"June",
+	"July",
+	"August",
+	"September",
+	"October",
+	"November",
+	"December",
+};
+
+int days_in_months[] = {
+	31, 0, 31, 30, 31, 30, 31,
+	31, 30, 31, 30, 31,
+};
+
+int main(int argc, char * argv[]) {
+	if (argc > 1) {
+		fprintf(stderr, "%s: arguments not currently supported\n", argv[0]);
+		return 1;
+	}
+	struct timeval now;
+	gettimeofday(&now, NULL);
+
+	struct tm actual;
+	struct tm * timeinfo;
+	timeinfo = localtime((time_t *)&now.tv_sec);
+	memcpy(&actual, timeinfo, sizeof(struct tm));
+	timeinfo = &actual;
+
+	char month[20];
+	sprintf(month, "%s %d", month_names[timeinfo->tm_mon], timeinfo->tm_year + 1900);
+
+	int len = (20 - strlen(month)) / 2;
+	while (len > 0) {
+		printf(" ");
+		len--;
+	}
+
+	/* Heading */
+	printf("%s\n", month);
+	printf("Su Mo Tu We Th Fr Sa\n");
+
+	/* Now's the fun part. */
+
+	int days_in_month = days_in_months[timeinfo->tm_mon];
+	if (days_in_month == 0) {
+		/* How many days in February? */
+		struct tm tmp;
+		memcpy(&tmp, timeinfo, sizeof(struct tm));
+		tmp.tm_mday = 29;
+		tmp.tm_hour = 12;
+		time_t tmp3 = mktime(&tmp);
+		struct tm * tmp2 = localtime(&tmp3);
+		if (tmp2->tm_mday == 29) {
+			days_in_month = 29;
+		} else {
+			days_in_month = 28;
+		}
+	}
+
+	int mday = timeinfo->tm_mday;
+	int wday = timeinfo->tm_wday; /* 0 == sunday */
+
+	while (mday > 1) {
+		mday--;
+		wday = (wday + 6) % 7;
+	}
+
+	for (int i = 0; i < wday; ++i) {
+		printf("   ");
+	}
+
+	while (mday <= days_in_month) {
+		if (mday == timeinfo->tm_mday) {
+			printf("\033[7m%2d\033[0m ", mday);
+		} else {
+			printf("%2d ", mday);
+		}
+
+		if (wday == 6) {
+			printf("\n");
+		}
+
+		mday += 1;
+		wday = (wday + 1) % 7;
+	}
+
+	if (wday != 0) {
+		printf("\n");
+	}
+
+	return 0;
+}
+