linux常用C头文件及函数详解(中文)

ipc SYSNOPSIS int sys_ipc (uint call, int first, int second, int third, void *ptr); PARAMETERS call: [in] the ipc call to perform. first, second, third: parameters. Depend on call. ptr: [in] pointer to a buffer. DESCRIPTION This is an in kernel wrapper for other ipc calls. call can take the following values: SEMOP sys_semop(first, (struct sembuf *)ptr, second); SEMGET sys_semget (first, second, third); SEMCTL sys_semctl (first, second, third, ptr); MSGSND sys_msgsnd (first, (struct msgbuf *) ptr, second, third); MSGRCV This one is a little tricky... struct ipc_kludge tmp; if (!ptr) return -EINVAL; memcpy_fromfs (&tmp,(struct ipc_kludge *) ptr, sizeof (tmp)); return sys_msgrcv (first, tmp.msgp, second, tmp.msgtyp, third); MSGGET sys_msgget ((key_t) first, second); MSGCTL sys_msgctl (first, second, (struct msqid_ds *) ptr); SHMAT sys_shmat (first, (char *) ptr, second, (ulong *) third); SHMDT sys_shmdt ((char *)ptr); SHMGET sys_shmget (first, second, third); SHMCTL sys_shmctl (first, second, (struct shmid_ds *) ptr); ************************************************************************************** msgctl SYNOPSIS int msgctl(int msqid,int cmd,struct msqid_ds *buf); PARAMETERS msqid: [in] the message queue to manipulate. cmd: [in] the operation to perform on the message queue. buf: the interpretation of this parameter depends on cmd. DESCRIPTION Manipulates a message queue. cmd may be one of: IPC_STAT retreives some information on the queue. IPC_SET modify some operating parameters of the queue. buf points to a msqid_ds structure. The only modifiable parameters are: msg_perm.uid, msg_perm.gid, msg_perm.mode (only lowest 9 bits) and msg_qbytes. The calling task uid must be one of the creator uid or the owner uid of the queue or the superuser uid. Only the superuser may rise msg_qbytes beyond the system limit of MSGMNB. IPC_RMID immediately destroys the message queue and awake all sleaping reader and writer processes. RETURN VALUE On success zero is returned. On error -1 is returned and errno is set to one of the following values: EACCESS: the caller tried IPC_STAT but does not have read permission on the queue. EIDRM: the queue is already removed. EINVAL: invalid value for cmd or msqid. EPERM: the taks tried an operation for which it does not have the necessary privileges. EFAULT. ************************************************************************************** msgget SYNOPSIS int msgget(key_t key, int msgflg); PARAMETERS key: [in] the message queue identifier to get. msgflg: [in] some flags (see description). DESCRIPTION Gets a message queue identifier. If key is IPC_PRIVATE, a new queue is created, otherwise the result depends on msgflg. The possible values for msgflg are: IPC_CREAT creates a new queue for the key if it does not already exist. IPC_EXCL if there is already a existing queue associated with key, the call fails. The 9 lower bits of msgflg specify the permission bits of the new queue. They have the same layout and meaning as those for files. However, the execute permissions are meaningless for queues. When creating a queue the system sets the appropriate parameters in the msqid_ds structure associated with the new queue. When accessing an already existing queue, the system simply check if the queue can be accessed. RETURN VALUE On success, the call returns the new queue identificator. On error -1 is returned and errno is set to one of the following values: EACCESS: the task has no access permission to the queue. EEXIST: IPC_CREAT and IPC_EXCL were specified and the queue already exists. EIDRM: the message queue no longer exists in the system. ENOENT: the message queue never existed. ENOSPC: the maximum number of message queues for the system has been reached. ENOMEM ************************************************************************************** msgrcv and msgsnd SYNOPSIS int msgsnd(int msqid, struct msgbuf *msgp, int msgsz, int msgflg); int msgrcv(int msqid, struct msgbuf *msgp, int msgsz, long msgtyp, int msgflg); PARAMETERS msqid: [in] the message queue. msgp: for msgsnd, [in] points to the message to send. For msgrcv, [out] points to the buffer where to put the message. msgsz: [in] size of the mtext part of the buffer. The maximum possible size is MSGMAX and is currently 4080 bytes. msgflg: [in] flags (see description). msgtyp: [in] the type of message to receive. DESCRIPTION msgp must point to a buffer having the following structure: struct msgbuf { long mtype; /* message type, must > 0 */ char mtext[1]; /* message data */ } The calling process must have read permission on the queue to call msgrcv and write permission on the queue to call msgsnd. msgsnd tries to enqueue the message. If msglfg is set to IPC_NOWAIT and the queue is full, the call fails. Otherwise the call blocks. If the send succeed, the message queue structure is updated as follow: msg_lspid is set to the pid of the calling process. msg_qnum is incremented by 1. msg_stime is set to the current time. msgrcv dequeues a message from the message queue. If the message to be dequeued has a length greater than msgsz, then the call fails. If the length is greater but the MSG_NOERROR flag is specified, the message gets truncated (and the truncated information is lost forever). The message to be dequeued can be choosed by the following values of msgtyp: msgtyp equals 0: in this case the 1st message on the queue is dequeued. msgtyp is greater than 0: if the flag MSG_EXCEPT is not specified, the first message of type msgtyp on the queue will be dequeued, otherwise the first message not of type msgtyp on the queue will be dequeued. msgtyp is less than 0: the first message of type in the range [1,-msgtyp] will be dequeued. If the flag IPC_NOWAIT is specified and there is no message of the specified type on the message queue, the call will fail, otherwise the call will block. On success, the queue data structure is updated as follow: msg_lrpid is set to the pid of the calling process. msg_qnum is decremented by 1. msg_rtime is set to the current time. RETURN VALUE On success msgsnd returns zero and msgrcv returns the number of bytes copied in the mtext array. On error -1 is returned and errno is set to one of the following values: for msgsnd: EAGAIN: IPC_NOWAIT was specified and the queue is full. EACCESS: the calling task does not have write permission on the queue. EIDRM: the queue has been removed. EINVAL: invalid msqid, msgsz or mtype value. EFAULT, EINTR and ENOMEM. for msgrcv: E2BIG: MSG_NOERROR is not specified and the message that should be dequeued is too bigger than msgsz. EACCESS: the calling task does not have read permission on the queue. EIDRM: the queue has been removed. EINVAL: invalid msqid or msgsz value. ENOMSG: IPC_NOWAIT was specified no message of the specified type is on the queue. EFAULT, EINTR ************************************************************************************** semctl SYNOPSIS int semctl(int semid, int semnun, int cmd, union semun arg); PARAMETERS semid: [in] the semaphore set to manipulate. semnum: [in] the semaphore in the set to manipulate (0 is the first). cmd: [in] the operation to perform. arg: [in out] an argument to the operation (see description). DESCRIPTION Manipulates a semaphore set or members of a semaphore set. The possible values for cmd are: IPC_STAT gets some information on the semaphore set. The calling task must have read access to the semaphore set. IPC_SET modify some members of the semid_ds structure