no longer reliant on libio

sleep/Makefile

@@ -0,0 +1,7 @@
+sleep: sleep.c
+	$(CC) -g -o sleep sleep.c
+
+clean:
+	rm -f sleep
+
+.PHONY: clean

sleep/sleep.c

@@ -1,23 +1,23 @@
 #include <ctype.h> /* isdigit(3) */
-#include <stdlib.h> /* atoi(3) */
+#include <errno.h> /* errno */
+#include <stdio.h> /* fprintf(3), stderr */
+#include <stdlib.h> /* strtol(3) */
 #include <sysexits.h> /* EX_USAGE */
 #include <unistd.h> /* sleep(3) */
-#include "libio.h"
 
 static char *program_name = "sleep";
 
 int main(int argc, char **argv){
 	int s;
+	extern int errno;
+
 	if(argc != 2){
-usage:		write(2, "Usage: ", 7);
-		fdprint(2, argv[0] == NULL ? program_name : argv[0]);
-		write(2, " [seconds]\n", 11);
+usage:		fprintf(stderr, "Usage: %s [seconds]\n", argv[0] == NULL ? program_name : argv[0]);
 		return EX_USAGE;
 	}
-	s = parse_uint(argv[1]);
-	while(isdigit(*argv[1]))
-		++argv[1];
-	if(*argv[1] != '\0')
+	errno = 0;
+	s = strtol(argv[1], &argv[1], 10);
+	if(*argv[1] != '\0' || errno != 0)
 		goto usage;
 	while(s > 0)
 		s = sleep(s);