sockatmark(3) [osf1 man page]
sockatmark(3) Library Functions Manual sockatmark(3) NAME
sockatmark - Tests whether a socket is at the out-of-band mark LIBRARY
Standard C Library: (libc.so, libc.a) SYNOPSIS
#include <sys/socket.h> int sockatmark (int socket); STANDARDS
The sockatmark function also supports POSIX.1g Draft 6.6. Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies the file descriptor associated with a socket. DESCRIPTION
The sockatmark() function enables applications to determine which received data precede the out-of-band data and which data follow the out- of-band data. The function uses the file descriptor for the socket to locate the data. Applications typically use this function between receive operations. The sockatmark() function does not remove the mark from the stream. RETURN VALUES
Upon successful completion, the sockatmark() function returns 1 if the protocol has marked the data stream and all data preceding the mark have been read, or 0 (zero) if there is no mark or if data precede the mark in the receive queue. If the sockatmark() function fails, a value of -1 is returned and errno is set to indicate the error. ERRORS
If the sockatmark() function fails, errno may be set to one of the following values: The socket parameter is not a valid file descriptor. The socket parameter does not specify a descriptor for a socket. RELATED INFORMATION
Functions: recv(2), recvmsg(2). Standards: standards(5). delim off sockatmark(3)
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sockatmark(3N) sockatmark(3N) NAME
sockatmark() - determine whether a socket is at the out-of-band mark SYNOPSIS
DESCRIPTION
The function determines whether the socket specified by the descriptor is at the out-of-band data mark. If the protocol for the socket supports out-of-band data by marking the stream with an out-of-band mark, the function returns 1 when all data preceding the mark has been read and the out-of-band mark is the first element in the receive queue. The function does not remove the mark from the stream. X/Open Sockets Only is new in RETURN VALUES
Upon successful completion, the function returns a value indicating whether the socket is at an out-of-band data mark: If the protocol has marked the data stream and all data preceding the mark has been read. If there is no mark, or if data precedes the mark in the receive queue. On failure, returns and sets to indicate the error. ERRORS
If fails, is set to one of the following values: The argument is not a valid file descriptor. The argument does not specify a descriptor for a socket. APPLICATION USAGE
The use of this function between receive operations allows an application to determine which received data precedes the out-of-band data and which follows the out-of-band data. There is an inherent race condition in the use of this function. On an empty receive queue, the current read of the location might be at the "mark". However, the system has no way of knowing that the next data segment arriving from the network is carrying the mark. Then returns false, and the next read operation silently consumes the mark. Hence, this function can only be used reliably in one or both ways: o when the application already knows that the out-of-band data has been seen by the system o and that it knows data is waiting to be read at the socket (by using or AUTHOR
was developed by HP and IEEE. SEE ALSO
ioctl(2), pselect(2), recv(2), recvmsg(2), socket(7). STANDARDS CONFORMANCE
sockatmark(3N)