sockatmark(3) — Справочная страница Linux

sockatmark(3)           Library Functions Manual           sockatmark(3)

ИМЯ

       sockatmark - determine whether socket is at out-of-band mark

БИБЛИОТЕКА

       Standard C library (libc, -lc)

СИНТАКСИС

       #include <sys/socket.h>

       int sockatmark(int sockfd);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       sockatmark():
           _POSIX_C_SOURCE >= 200112L

ОПИСАНИЕ

       sockatmark() 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.

ЗНАЧЕНИЕ, ВОЗВРАЩАЕМОЕ ФУНКЦИЕЙ

       A 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.

ОШИБКИ

       EBADF  sockfd is not a valid file descriptor.

       EINVAL sockfd is not a file descriptor to which sockatmark() can
              be applied.

АТРИБУТЫ

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ sockatmark()                        │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

СТАНДАРТЫ

       POSIX.1-2008.

ИСТОРИЯ

       glibc 2.2.4.  POSIX.1-2001.

ПРИМЕЧАНИЯ

       If 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.

НЕДОСТАТКИ

       Prior to glibc 2.4, sockatmark() did not work.

ПРИМЕРЫ

       The 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");
                   ...
               }
           }

СМОТРИТЕ ТАКЖЕ

       fcntl(2), recv(2), send(2), tcp(7)

КОЛОФОН

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       man-pages@man7.org

Linux man-pages 6.9.1          2024-05-02                  sockatmark(3)

Страницы, которые ссылаются на эту страницу: recv(2), signal-safety(7)