init

.gitignore

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+clock
+clock~

Makefile

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+#!/bin/make -f
+
+CFLAGS   := -std=c99 -Os -s -Wall -Wextra -Wpedantic
+CPPFLAGS :=
+INSTALL  := /usr/local
+PROGN    := clock
+
+$(PROGN): clock.c
+	$(CC) $(CFLAGS) -pipe -o $@ $<
+	gzexe $@
+
+clean:
+	-rm $(PROGN) $(PROGN)~
+
+install: $(PROGN)
+	install -m 755 $< $(INSTALL)/bin/
+
+.PHONY: clean install all

README

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+/-------------------------------\
+|             Clock             |
+\-------------------------------/
+
+It's just a clock.
+
+The executable is compressed, if you compile it and it fails to run, run `mv clock~ clock` and try again.
+
+Building: make or baked
+
+          CPPFLAGS='...
+          PERIOD      - Inteval which the clock will update by.
+          CLEAR       - The control code for clearing the terminal.
+          CLEAR_DUMB  - How it clears on a dumb terminal, 127 newlines is enough.
+          '
+
+          These definitions may be omitted without issue.
+
+Installing: make install INSTALL=/usr/local PROGN=clock
+            INSTALL - Installation location, should be somewhere within the PATH.
+            PROGN   - A overridable program name, change it if you want to.
+
+Licensed under the public domain.
+
+This line makes the README as exactly as long as the code.

clock.c

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+/* clock.c - Public Domain - It's a digital clock
+EXEC:
+  cc -O1 -s -pipe -Wall -Wextra -Wpedantic $CPPFLAGS -o clock clock.c && gzexe clock
+:STOP */
+#include <time.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#ifndef CLEAR
+# define CLEAR "\033[2J"
+#endif
+
+#ifndef CLEAR_DUMB
+# define CLEAR_DUMB "\n"
+#endif
+
+#ifndef PERIOD
+# define PERIOD 5
+#endif
+
+char * hmstime(struct tm * tm)
+{
+  static char time[9];
+  sprintf(time, "%.2d:%.2d:%.2d",
+          tm->tm_hour, tm->tm_min, tm->tm_sec);
+  return time;
+}
+
+int
+main(void)
+{
+  struct tm * tm;
+  time_t now;
+  int sec;
+
+  puts("Type C-c to exit.\n");
+
+  for (;;)
+  {
+    time(&now);
+    tm = gmtime(&now);
+    /* Junk character may be printed, this is the time to get a new terminal. */
+    printf(CLEAR " %s\n" CLEAR_DUMB, hmstime(tm));
+    sec = tm->tm_sec % PERIOD;
+    sleep(!sec ? PERIOD : PERIOD - sec);
+  }
+
+  return 0;
+}