altio/t_select.c

+/* t_select.c
+
+   Example of the use of the select() system call to monitor multiple
+   file descriptors.
+
+   Usage as shown in usageError().
+*/
 #include <sys/time.h>
+#if ! defined(__hpux)
+/* HP-UX 11 doesn't have this header file */
 #include <sys/select.h>
+#endif
 #include "tlpi_hdr.h"
 
 static void
 usageError(const char *progName)
 {
     fprintf(stderr, "Usage: %s {timeout|-} fd-num[rw]...\n", progName);
     fprintf(stderr, "    - means infinite timeout; \n");
     fprintf(stderr, "    r = monitor for read\n");
     fprintf(stderr, "    w = monitor for write\n\n");
     fprintf(stderr, "    e.g.: %s - 0rw 1w\n", progName);
     exit(EXIT_FAILURE);
 }
 
 int
 main(int argc, char *argv[])
 {
     fd_set readfds, writefds;
     int ready, nfds, fd, numRead, j;
     struct timeval timeout;
     struct timeval *pto;
     char buf[10];                       /* Large enough to hold "rw\0" */
 
     if (argc < 2 || strcmp(argv[1], "--help") == 0)
         usageError(argv[0]);
 
     /* Timeout for select() is specified in argv[1] */
 
     if (strcmp(argv[1], "-") == 0) {
         pto = NULL;                     /* Infinite timeout */
     } else {
         pto = &timeout;
         timeout.tv_sec = getLong(argv[1], 0, "timeout");
         timeout.tv_usec = 0;            /* No microseconds */
     }
 
     /* Process remaining arguments to build file descriptor sets */
 
     nfds = 0;
     FD_ZERO(&readfds);
     FD_ZERO(&writefds);
 
     for (j = 2; j < argc; j++) {
         numRead = sscanf(argv[j], "%d%2[rw]", &fd, buf);
         if (numRead != 2)
             usageError(argv[0]);
         if (fd >= FD_SETSIZE)
             cmdLineErr("file descriptor exceeds limit (%d)\n", FD_SETSIZE);
 
         if (fd >= nfds)
             nfds = fd + 1;              /* Record maximum fd + 1 */
         if (strchr(buf, 'r') != NULL)
             FD_SET(fd, &readfds);
         if (strchr(buf, 'w') != NULL)
             FD_SET(fd, &writefds);
     }
 
     /* We've built all of the arguments; now call select() */
 
     ready = select(nfds, &readfds, &writefds, NULL, pto);
                                         /* Ignore exceptional events */
     if (ready == -1)
         errExit("select");
 
     /* Display results of select() */
 
     printf("ready = %d\n", ready);
     for (fd = 0; fd < nfds; fd++)
         printf("%d: %s%s\n", fd, FD_ISSET(fd, &readfds) ? "r" : "",
                 FD_ISSET(fd, &writefds) ? "w" : "");
 
     if (pto != NULL)
         printf("timeout after select(): %ld.%03ld\n",
                (long) timeout.tv_sec, (long) timeout.tv_usec / 1000);
     exit(EXIT_SUCCESS);
 }