Several linux apt duplicate the api beneath the ip

Several API:
key_t ftok (char * pathname, char proj);
it returns the corresponding pathname with the route to a key. This function does not manipulate instantly aboard the information queue, merely the phone msgget () to obtain the information queue descriptor ago, often have to call the function. A typical use of key = ftok ('.', 'a');

int msgget (key_t key, int msgflg)
key is a key parameter values ​​obtained by the ftok; msgflg parameters are flags. This call returns the value of the key health message queue corresponding descriptor.
in two cases, the call will build a fashionable message queue:
If there is no message queue with the health value of the corresponding key, and contains IPC_CREAT msgflg flag; key parameters IPC_PRIVATE; parameters msgflg because the following: IPC_CREAT, IPC_EXCL,GHD Red Butterfly 2011, IPC_NOWAIT or 3 alternatively results.

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

int msgrcv (int msqid, struct msgbuf * msgp,GHD Green Butterfly 2011, int msgsz,GHD IV Salon Straighteners, long msgtyp, int msgflg);
msgid representative of the system call from the message queue to peruse a message and the message is cached in the msgp points msgbuf structure.
msqid for the message queue descriptor; message return residence stored in the msgp point, msgsz msgbuf the mtext members specified length (ie the width of the message content),GHD Straighteners, msgtyp read the message type for the request; can read the message signs msgflg constant value for the emulating or:
IPC_NOWAIT message if the conditions are not met, the call returns immediately, this period, errno = ENOMSG IPC_EXCEPT and msgtyp> 0 with the use and return the queue type is not the 1st newspaper 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 part will be lost. msgrcv manual details the type of the message to take alter 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 tangible number of bytes, otherwise -1.
integer msgsnd (int msqid, struct msgbuf * msgp, int msgsz, int msgflg);
msgid representative to the message queue to send 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 significant msgflg logo IPC_NOWAIT, specified in the message queue is insufficient space to mail the message, msgsnd is to await. Caused by msgsnd () to wait for two conditions:
the size of the present message with the current number of bytes in the message queue and extra than a message queue of the aggregate capacity; the current message queue digit (element ) not fewer than the total capacity of the message queue (in msgsnd () There are three conditions for unblocking:
does not meet the above 2 conditions, namely the message queue space to adjust the message; msqid representatives message queue is deleted; profession msgsnd () the process is disturbed by a whistle; call Returns: returns 0 on 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 operation, there are three bat operation: IPC_STAT, IPC_SET,GHD IV Styling Set, IPC_RMID.
IPC_STAT: This bid is used to get message queue information, the returned message is stored in buf points to msqid structure; IPC_SET: This command is used to set message queue attributes, to set the attributes are stored in the buf structure pointed to msqid in; can set attributes include: msg_perm.uid,GHD IV Pink Straighteners, msg_perm.gid, msg_perm.mode and msg_qbytes, also affect the msg_ctime members. IPC_RMID: erase the message queue identified msqid; call returns: success returns 0, otherwise returns -1.