Query: sockatmark
OS: minix
Section: 3
Links: minix man pages all man pages
Forums: forum home forum categories
Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar
SOCKATMARK(3) Linux Programmer's Manual SOCKATMARK(3)NAMEsockatmark - determine whether socket is at out-of-band markSYNOPSIS#include <sys/socket.h> int sockatmark(int sockfd); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sockatmark(): _POSIX_C_SOURCE >= 200112LDESCRIPTIONsockatmark() returns a value indicating whether or not the socket referred to by the file descriptor sockfd is at the out-of-band mark. If the socket is at the mark, then 1 is returned; if the socket is not at the mark, 0 is returned. This function does not remove the out-of- band mark.RETURN VALUEA successful call to sockatmark() returns 1 if the socket is at the out-of-band mark, or 0 if it is not. On error, -1 is returned and errno is set to indicate the error.ERRORSEBADF sockfd is not a valid file descriptor. EINVAL sockfd is not a file descriptor to which sockatmark() can be applied.VERSIONSsockatmark() was added to glibc in version 2.2.4.ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7). +-------------+---------------+---------+ |Interface | Attribute | Value | +-------------+---------------+---------+ |sockatmark() | Thread safety | MT-Safe | +-------------+---------------+---------+CONFORMING TOPOSIX.1-2001, POSIX.1-2008.NOTESIf sockatmark() returns 1, then the out-of-band data can be read using the MSG_OOB flag of recv(2). Out-of-band data is supported only on some stream socket protocols. sockatmark() can safely be called from a handler for the SIGURG signal. sockatmark() is implemented using the SIOCATMARK ioctl(2) operation.BUGSPrior to glibc 2.4, sockatmark() did not work.EXAMPLEThe following code can be used after receipt of a SIGURG signal to read (and discard) all data up to the mark, and then read the byte of data at the mark: char buf[BUF_LEN]; char oobdata; int atmark, s; for (;;) { atmark = sockatmark(sockfd); if (atmark == -1) { perror("sockatmark"); break; } if (atmark) break; s = read(sockfd, buf, BUF_LEN); if (s == -1) perror("read"); if (s <= 0) break; } if (atmark == 1) { if (recv(sockfd, &oobdata, 1, MSG_OOB) == -1) { perror("recv"); ... } }SEE ALSOfcntl(2), recv(2), send(2), tcp(7)COLOPHONThis page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. Linux 2017-09-15 SOCKATMARK(3)