07-04-2001
UNIX Internals, Help required...
I know UNIX user level commands, shell scripts. But i have no idea about kernel level programming and networking. I know the terms semaphore,IPC,socket programming. But i don't know in details what are these. I need to know the following.
1. Unix kernel level programming.
2. Unix Internals.
3. Unix networking.
Please suggest me some good books as well as any tutorials on net which could give me the above knowledge including semaphores,IPC,socket programming,TCP/IP.
Thanks.
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LEARN ABOUT OPENDARWIN
semget
SEMGET(2) BSD System Calls Manual SEMGET(2)
NAME
semget -- obtain a semaphore id
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
int
semget(key_t key, int nsems, int flag);
DESCRIPTION
Based on the values of key and flag, semget() returns the identifier of a newly created or previously existing set of semaphores. The key is
analogous to a filename: it provides a handle that names an IPC object. There are three ways to specify a key:
o IPC_PRIVATE may be specified, in which case a new IPC object will be created.
o An integer constant may be specified. If no IPC object corresponding to key is specified and the IPC_CREAT bit is set in flag, a new one
will be created.
o The ftok(3) function may be used to generate a key from a pathname.
The mode of a newly created IPC object is determined by OR'ing the following constants into the flag argument:
SEM_R Read access for user.
SEM_A Alter access for user.
(SEM_R>>3) Read access for group.
(SEM_A>>3) Alter access for group.
(SEM_R>>6) Read access for other.
(SEM_A>>6) Alter access for other.
If a new set of semaphores is being created, nsems is used to indicate the number of semaphores the set should contain. Otherwise, nsems may
be specified as 0.
RETURN VALUES
The semget() system call returns the id of a semaphore set if successful; otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
The semget() system call will fail if:
[EACCES] Access permission failure.
[EEXIST] IPC_CREAT and IPC_EXCL were specified, and a semaphore set corresponding to key already exists.
[EINVAL] The number of semaphores requested exceeds the system imposed maximum per set.
[ENOSPC] Insufficiently many semaphores are available.
[ENOSPC] The kernel could not allocate a struct semid_ds.
[ENOENT] No semaphore set was found corresponding to key, and IPC_CREAT was not specified.
SEE ALSO
semctl(2), semop(2), ftok(3)
BSD
September 12, 1995 BSD