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select is a system call and application programming interface (API) in Unix-like and POSIX-compliant operating systems for examining the status of file descriptors of open input/output channels. The select system call is similar to the ''poll'' facility introduced in UNIX System V and later operating systems. In the C programming language, the select system call is declared in the header file sys/select.h or unistd.h, and has the following syntax: int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout); fd_set type arguments may be manipulated with four utility macros: FD_SET(), FD_CLR(), FD_ZERO(), and FD_ISSET().Select returns the total number of bits set in readfds, writefds and errorfds, or zero if the timeout expired, and -1 on error. The sets of file descriptor used in select are finite in size, depending on the operating system. The newer system call ''poll'' provides a more flexible solution. == Example == #include #include #include #include #include #include #include #include #include #include #include #include #define PORT "9421" / * function prototypes */ void die(const char *); int main(int argc, char * *argv) if (-1 == (bind(sockfd, res->ai_addr, res->ai_addrlen))) break; } if (-1 == sockfd) exit(EXIT_FAILURE); freeaddrinfo(res0); if (-1 == (listen(sockfd, 32))) die("listen()"); if (-1 == (fcntl(sockfd, F_SETFD, O_NONBLOCK))) die("fcntl()"); FD_ZERO(&master); FD_ZERO(&readfds); FD_SET(sockfd, &master); maxfd = sockfd; while (1) } else } } } return 0; } void die(const char *msg) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Select (Unix)」の詳細全文を読む スポンサード リンク
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