信号驱动的IO

（1）client1，基于SIGIO的写法：

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <fcntl.h>

 #include <unistd.h>

 #include <signal.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <errno.h>

 #define BUFSIZE 128

 static int fdr;

 static int fdw;

 static void handler(int unuse)

 {

     int ret;

     char buf[BUFSIZE];

     ret = read(fdr, buf, BUFSIZE);

     if (ret == -) {

         return;

     }

     if (ret == ) {

         exit();

     }

     write(, "\033[31m", );

     write(, buf, ret);

     write(, "\033[0m", );

 }

 int main(void)

 {

     int ret;

     char buf[BUFSIZE];

     long flags;

     signal(SIGIO, handler);

     fdr = open("f1", O_RDONLY);

     if (fdr == -) {

         perror("f1");

         goto open_fdr_err;

     }

     fdw = open("f2", O_WRONLY);

     if (fdw == -) {

         perror("f2");

                 goto open_fdw_err;

     }

     flags = fcntl(fdr, F_GETFL);

     flags |= O_ASYNC;

     fcntl(fdr, F_SETFL, flags);

     fcntl(fdr, F_SETOWN, getpid());

     while () {

         ret = read(, buf, BUFSIZE);

         if (ret == -) {

             if (errno == EINTR) {

                 continue;

             }

             perror("read()");

             break;

         }

         if (ret == ) {

             break;

         }

         write(fdw, buf, ret);

     }

     close(fdw);

     close(fdr);

     return ;

     close(fdw);

 open_fdw_err:

     close(fdr);

 open_fdr_err:

     return ;

 }

client1，基于自定义信号的写法：

 #define _GNU_SOURCE

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <fcntl.h>

 #include <unistd.h>

 #include <signal.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <errno.h>

 #define BUFSIZE 128

 static int fdr;

 static int fdw;

 static void handler(int unuse)

 {

     int ret;

     char buf[BUFSIZE];

     ret = read(fdr, buf, BUFSIZE);

     if (ret == -) {

         return;

     }

     if (ret == ) {

         exit();

     }

     write(, "\033[31m", );

     write(, buf, ret);

     write(, "\033[0m", );

 }

 int main(void)

 {

     int ret;

     char buf[BUFSIZE];

     long flags;

     signal(SIGUSR1, handler);

     fdr = open("f1", O_RDONLY);

     if (fdr == -) {

         perror("f1");

         goto open_fdr_err;

     }

     fdw = open("f2", O_WRONLY);

     if (fdw == -) {

         perror("f2");

                 goto open_fdw_err;

     }

     flags = fcntl(fdr, F_GETFL);

     flags |= O_ASYNC;

     fcntl(fdr, F_SETFL, flags);

     fcntl(fdr, F_SETOWN, getpid());

     fcntl(fdr, F_SETSIG, SIGUSR1);

     while () {

         ret = read(, buf, BUFSIZE);

         if (ret == -) {

             if (errno == EINTR) {

                 continue;

             }

             perror("read()");

             break;

         }

         if (ret == ) {

             break;

         }

         write(fdw, buf, ret);

     }

     close(fdw);

     close(fdr);

     return ;

     close(fdw);

 open_fdw_err:

     close(fdr);

 open_fdr_err:

     return ;

 }

（2）client2：

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <fcntl.h>

 #include <signal.h>

 #include <unistd.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <errno.h>

 #define BUFSIZE 128

 static int fdr;

 static int fdw;

 static void handler(int unuse)

 {

     int ret;

     char buf[BUFSIZE];

     ret = read(fdr, buf, BUFSIZE);

     if (ret == -) {

         return;

     }

     if (ret == ) {

         exit();

     }

     write(, "\033[31m", );

     write(, buf, ret);

     write(, "\033[0m", );

 }

 int main(void)

 {

     int ret;

     char buf[BUFSIZE];

     long flags;

     signal(SIGIO, handler);

     fdw = open("f1", O_WRONLY);

     if (fdw == -) {

         perror("f1");

                 goto open_fdw_err;

     }

     fdr = open("f2", O_RDONLY);

     if (fdr == -) {

         perror("f2");

         goto open_fdr_err;

     }

     flags = fcntl(fdr, F_GETFL);

     flags |= O_ASYNC;

     fcntl(fdr, F_SETFL, flags);

     fcntl(fdr, F_SETOWN, getpid());

     while () {

         ret = read(, buf, BUFSIZE);

         if (ret == -) {

             if (errno == EINTR) {

                 continue;

             }

             perror("read()");

             break;

         }

         if (ret == ) {

             break;

         }

         write(fdw, buf, ret);

     }

     close(fdr);

     close(fdw);

     return ;

     close(fdr);

 open_fdr_err:

     close(fdw);

 open_fdw_err:

     return ;

 }