Several linux apt duplicate the api below the ipc

Several API:
key_t ftok (char * pathname, char proj);
it returns the corresponding pathname with the way to a key. This function does not manipulate directly on the message queue, yet the call msgget () to get the message queue descriptor ago, often must call the function. A typical use of key = ftok ('.', 'a');

int msgget (key_t key, int msgflg)
opener namely a opener parameter values ​​obtained by the ftok; msgflg parameters are flags. This call returns the worth of the key health message queue corresponding descriptor.
in two cases,GHD Leopard Grain, the call will establish a new message queue:
If there is no message queue with the health value of the corresponding key,GHD MK4 Gold Straighteners, and contains IPC_CREAT msgflg flag; key parameters IPC_PRIVATE; parameters msgflg for the following: IPC_CREAT, IPC_EXCL, IPC_NOWAIT alternatively 3 or results.

call returns: the successful return message queue descriptor, otherwise it returns -1.

int msgrcv (int msqid, struct msgbuf * msgp, int msgsz, long msgtyp, int msgflg);
msgid representative of the system call from the message queue to read a message and the message is stored in the msgp points msgbuf structure.
msqid as the message queue descriptor; message return residence stored in the msgp point,GHD Diamond Flag 2011, msgsz msgbuf the mtext members specified width (ie the length of the message content), msgtyp peruse the message type for the request; tin peruse the message signs msgflg constant value for the emulating or:
IPC_NOWAIT message if the conditions are not met, the call returns instantly, this time, errno = ENOMSG IPC_EXCEPT and msgtyp> 0 with the use and return the queue type is not the first news of IPC_NOERROR msgtyp If the queue is greater than the message content to meet the conditions requested msgsz bytes, put the message truncated, the truncated portion will be lost. msgrcv manual details the type of the message to take differ values ​​(> 0; <0; = 0), the call will return the message queue in which messages.
msgrcv () There are three conditions for unblocking:
must meet the conditions of the message queue the message; msqid representatives message queue is deleted; call msgrcv () the process is interrupted by a signal; call returns: the successful return time the message of the actual digit of bytes, otherwise -1.
integer msgsnd (int msqid, struct msgbuf * msgp, int msgsz, int msgflg);
msgid representative to the message queue to bring a message, send the message be stored in the msgp msgbuf pointed to the structure, the size of the message specified by the msgze.
for sending messages, the meaningful msgflg logo IPC_NOWAIT, specified in the message queue is insufficient space to send the message, msgsnd is to wait. Caused by msgsnd () to wait for two conditions:
the size of the current message with the present number of bytes in the message queue and extra than a message queue of the total capability; the present message queue number (element ) not fewer than the total capability of the message queue (in msgsnd () There are three conditions for unblocking:
does no meet the on two conditions, is the message queue space apt adjust the message; msqid representatives message queue is canceled; calling msgsnd () the process is disturbed by a semaphore; call Returns: returns 0 ashore success, otherwise returns -1.
int msgctl (int msqid, int cmd, struct msqid_ds * buf);
the system call to the message queue identified by the implementation of msqid cmd action, there are three cmd operation: IPC_STAT, IPC_SET,GHD Purple Butterfly 2011, IPC_RMID.
IPC_STAT: This directive is accustom to get message queue message, the returned message is stored in buf points to msqid structure; IPC_SET: This bid is used to set message queue attributes,GHD Green Straighteners, to set the attributes are stored in the buf structure pointed to msqid in; can set attributes include: msg_perm.uid, msg_perm.gid, msg_perm.mode and msg_qbytes, likewise influence the msg_ctime members. IPC_RMID: delete the message queue identified msqid; call returns: success returns 0,GHD NZ, otherwise returns -1.