RPC_PEERADDR(9) Linux Networking RPC_PEERADDR(9)NAME
rpc_peeraddr - extract remote peer address from clnt's xprt
SYNOPSIS
size_t rpc_peeraddr(struct rpc_clnt * clnt, struct sockaddr * buf, size_t bufsize);
ARGUMENTS
clnt
RPC client structure
buf
target buffer
bufsize
length of target buffer
DESCRIPTION
Returns the number of bytes that are actually in the stored address.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 RPC_PEERADDR(9)
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msgsnap(2) System Calls msgsnap(2)NAME
msgsnap - message queue snapshot operation
SYNOPSIS
#include <sys/msg.h>
msgsnap(int msqid, void *buf, size_t bufsz, long msgtyp);
DESCRIPTION
The msgsnap() function reads all of the messages of type msgtyp from the queue associated with the message queue identifier specified by
msqid and places them in the user-defined buffer pointed to by buf.
The buf argument points to a user-defined buffer that on return will contain first a buffer header structure:
struct msgsnap_head {
size_t msgsnap_size; /* bytes used/required in the buffer */
size_t msgsnap_nmsg; /* number of messages in the buffer */
};
followed by msgsnap_nmsg messages, each of which starts with a message header:
struct msgsnap_mhead {
size_t msgsnap_mlen; /* number of bytes in the message */
long msgsnap_mtype; /* message type */
};
and followed by msgsnap_mlen bytes containing the message contents.
Each subsequent message header is located at the first byte following the previous message contents, rounded up to a sizeof(size_t) bound-
ary.
The bufsz argument specifies the size of buf in bytes. If bufsz is less than sizeof(msgsnap_head), msgsnap() fails with EINVAL. If bufsz
is insufficient to contain all of the requested messages, msgsnap() succeeds but returns with msgsnap_nmsg set to 0 and with msgsnap_size
set to the required size of the buffer in bytes.
The msgtyp argument specifies the types of messages requested as follows:
o If msgtyp is 0, all of the messages on the queue are read.
o If msgtyp is greater than 0, all messages of type msgtyp are read.
o If msgtyp is less than 0, all messages with type less than or equal to the absolute value of msgtyp are read.
The msgsnap() function is a non-destructive operation. Upon completion, no changes are made to the data structures associated with msqid.
RETURN VALUES
Upon successful completion, msgsnap() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
The msgsnap() function will fail if:
EACCES Operation permission is denied to the calling process. See intro(2).
EINVAL The msqid argument is not a valid message queue identifier or the value of bufsz is less than sizeof(struct msgsnap_head).
EFAULT The buf argument points to an illegal address.
USAGE
The msgsnap() function returns a snapshot of messages on a message queue at one point in time. The queue contents can change immediately
following return from msgsnap().
EXAMPLES
Example 1: msgsnap() example
This is sample C code indicating how to use the msgsnap function (see msgids(2)).
void
process_msgid(int msqid)
{
size_t bufsize;
struct msgsnap_head *buf;
struct msgsnap_mhead *mhead;
int i;
/* allocate a minimum-size buffer */
buf = malloc(bufsize = sizeof(struct msgsnap_head));
/* read all of the messages from the queue */
for (;;) {
if (msgsnap(msqid, buf, bufsize, 0) != 0) {
perror("msgsnap");
free(buf);
return;
}
if (bufsize >= buf->msgsnap_size) /* we got them all */
break;
/* we need a bigger buffer */
buf = realloc(buf, bufsize = buf->msgsnap_size);
}
/* process each message in the queue (there may be none) */
mhead = (struct msgsnap_mhead *)(buf + 1); /* first message */
for (i = 0; i < buf->msgsnap_nmsg; i++) {
size_t mlen = mhead->msgsnap_mlen;
/* process the message contents */
process_message(mhead->msgsnap_mtype, (char *)(mhead+1), mlen);
/* advance to the next message header */
mhead = (struct msgsnap_mhead *)
((char *)mhead + sizeof(struct msgsnap_mhead) +
((mlen + sizeof(size_t) - 1) & ~(sizeof(size_t) - 1)));
}
free(buf);
}
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|MT-Level |Async-Signal-Safe |
+-----------------------------+-----------------------------+
SEE ALSO ipcrm(1), ipcs(1), intro(2), msgctl(2), msgget(2), msgids(2), msgrcv(2), msgsnd(2), attributes(5)SunOS 5.10 8 Mar 2000 msgsnap(2)