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Re: Linux ?= System-V ; BSD??




On Sat, 26 Sep 1998, Ze'ev Maor wrote:

> Is Linux suppose to be closer to System-V or to BSD ?? Mainly in those
> programming aspects
> in which they differ, such as: exsiting signals, file locks, semaphores etc.
> etc. little annoying
> differences...

as far as i could notice, linux (and all other systems) have stopped being
'sysV or BSD'. they eventually adopt newer standards (posix.*, for
example), and usually support relevant parts from both bsd and sysV.

for example: signals can be either auto-reseting or not, depends
on how you employ them (using signal(2) makes them reset automatically
when invoked, using sigaction does not do so). sysV IPC (i.e. semaphores,
message queues and shared memory) is supported, as is on most modern
unices.

networking: TLI (and its newer replacement, XTI) which are sysV, are not
supported on linux (AFAIK), while the bsd sockets interface is supported.

the system startup files format (/etc/rc.d/...) is similar to sysV, but
not exactly the same (in sysV, the various rcX.d directories reside
directly under /etc).

the printing system (/etc/printcap and lpd) is BSD based (in sysV there is
a more complicated system, check out how it works with solaris).

there is also the notion of restarting system calls vs non-restarting
system calls (i.e. if a system call was interupted by a signal, will it
resume when the signal handler returns, or does it return an error such as
EAGAIN, or EINTR ?) i'm not sure if this is BSD vs sysV, thought. as far
as i can tell, linux's system calls are non-restarting.


so as you can see, linux is a mish-mash of everything. it's not relevant
to say that it is 'more bsd-like' or 'more sysV-like'.  why do you need to
know this anyway?

guy

p.s. you can look at the bottom of almost every man page on linux, there
is a section titled 'Conforms to', which states for each system call and
library function which 'standards' it conforms to.