sysdeps/unix/sysv/linux/clock.c

   1 /* Return the time used by the program so far (user time + system time).
   2    Copyright (C) 1991-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/times.h>
  20 #include <time.h>
  21 #include <unistd.h>
  22
  23 clock_t
  24 clock (void)
  25 {
  26   struct timespec ts;
  27
  28   _Static_assert (CLOCKS_PER_SEC == 1000000,
  29                   "CLOCKS_PER_SEC should be 1000000");
  30
  31   /* clock_gettime shouldn't fail here since CLOCK_PROCESS_CPUTIME_ID is
  32      supported since 2.6.12.  Check the return value anyway in case the kernel
  33      barfs on us for some reason.  */
  34   if (__glibc_unlikely (__clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts) != 0))
  35     return (clock_t) -1;
  36
  37   return (ts.tv_sec * CLOCKS_PER_SEC
  38           + ts.tv_nsec / (1000000000 / CLOCKS_PER_SEC));
  39 }