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 ;
 }