[sclug] C programming question and date on Linux

[pieter claassen]

Hello All,

Here are two simple questions.
1. Why does C on linux have such cool undocumented data types such as
u_int16_y and where are they documented? My Kernighan and Ritchie says
nothing about them. How do I know when I write a program which ones I am
supposed to use? Also, if I look through the /net/ethernet.h I get the
following declaration

struct ether_header
{
  u_int8_t  ether_dhost[ETH_ALEN];      /* destination eth addr */
  u_int8_t  ether_shost[ETH_ALEN];      /* source ether addr    */
  u_int16_t ether_type;                 /* packet type ID field */
} __attribute__ ((__packed__));

What is the __attribute__((__packed__)); about and where can I get more
info on that? How do I find out where ETH_ALEN comes from?

2. My PC clock is always way out and it seems to stay out. Firstly, how
do I set daylight savings in the command line and is there a simpler way
to set the date than with date -s foo? Is there is way to stop this
problem (there must be time servers online with appropriate clients that
does this magic securely)?

Thanks,
Pieter
-- 
-----------------------------
Pieter Claassen
pieter at openauth.co.uk
http://www.openauth.co.uk

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