Initial programs from intro chapter

intro/io.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <string.h>
+
+int main(int argc, char *argv[]) {
+    int fd = open("/tmp/file", O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
+    assert(fd >= 0);
+    char buffer[20];
+    sprintf(buffer, "hello world\n");
+    int rc = write(fd, buffer, strlen(buffer));
+    assert(rc == (strlen(buffer)));
+    fsync(fd);
+    close(fd);
+    return 0;
+}
+