test/select/test01.c

   1 /*
   2  * Test name: test01.c
   3  *
   4  * Objective: The purpose of this test is to make sure that the timeout mechanisms
   5  * work without errors.
   6  *
   7  * Description: Executes a select as if it was a sleep and compares the time it
   8  * has been actually sleeping against the specified time in the select call.
   9  * Three cases are tested: first, a timeout specified in seconds, second, a timeout in
  10  * microseconds, and third, a timeout with more precision than seconds.
  11  *
  12  * Jose M. Gomez
  13  */
  14
  15 #include <sys/types.h>
  16 #include <sys/select.h>
  17 #include <sys/time.h>
  18 #include <time.h>
  19 #include <stdio.h>
  20 #include <errno.h>
  21 #include <string.h>
  22
  23 #define SECONDS 3
  24 #define USECONDS 3000000L
  25
  26 int main(void) {
  27         int r;
  28         time_t start, end;      /* variables for timing */
  29         struct timeval timeout; /* timeout structure */
  30
  31         /* Set timeout for 3 seconds */
  32         timeout.tv_sec = SECONDS;
  33         timeout.tv_usec = 0;
  34         printf("Sleeping now for %d seconds...\n", SECONDS);
  35         /* Record time before starting */
  36         start = time(NULL);
  37         r = select(0, NULL, NULL, NULL, &timeout);
  38         printf("select return code: %d error: %s\n",
  39                 r, strerror(errno));
  40         end = time(NULL);
  41         printf("For a timeout with select of %d seconds, it took %d actual seconds\n",
  42                 SECONDS, end-start);
  43
  44         /* Set timeout for 3 seconds , but specified in microseconds */
  45
  46         timeout.tv_sec = 0;
  47         timeout.tv_usec = USECONDS;
  48         printf("\n***************************\n");
  49         printf("Sleeping now for %ld microseconds...\n", USECONDS);
  50         /* Record time before starting */
  51         start = time(NULL);
  52         r = select(0, NULL, NULL, NULL, &timeout);
  53         printf("select return code: %d error: %s\n",
  54                 r, strerror(errno));
  55         end = time(NULL);
  56         printf("For a timeout with select of %ld useconds, it took %d actual seconds\n",
  57                 USECONDS, end-start);
  58
  59         /* Set timeout for 1.5 seconds, but specified in microseconds */
  60
  61         timeout.tv_sec = 0;
  62         timeout.tv_usec = USECONDS/2;
  63         printf("\n***************************\n");
  64         printf("Sleeping now for %ld microseconds...\n", USECONDS/2);
  65         /* Record time before starting */
  66         start = time(NULL);
  67         r = select(0, NULL, NULL, NULL, &timeout);
  68         printf("select return code: %d error: %s\n",
  69                 r, strerror(errno));
  70         end = time(NULL);
  71         printf("For a timeout with select of %ld useconds, it took %d actual seconds\n",
  72                 USECONDS/2, end-start);
  73         return 0;
  74 }