sysdeps/unix/sysv/linux/sysconf.c

   1 /* Get file-specific information about a file.  Linux version.
   2    Copyright (C) 2003, 2004, 2006 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdlib.h>
  23 #include <sysdep.h>
  24 #include <time.h>
  25 #include <unistd.h>
  26 #include <not-cancel.h>
  27
  28 static long int posix_sysconf (int name);
  29
  30
  31 /* Get the value of the system variable NAME.  */
  32 long int
  33 __sysconf (int name)
  34 {
  35   const char *procfname = NULL;
  36
  37   switch (name)
  38     {
  39 #ifdef __NR_clock_getres
  40     case _SC_MONOTONIC_CLOCK:
  41       /* Check using the clock_getres system call.  */
  42       {
  43         struct timespec ts;
  44         INTERNAL_SYSCALL_DECL (err);
  45         int r;
  46         r = INTERNAL_SYSCALL (clock_getres, err, 2, CLOCK_MONOTONIC, &ts);
  47         return INTERNAL_SYSCALL_ERROR_P (r, err) ? -1 : _POSIX_VERSION;
  48       }
  49 #endif
  50
  51 #if defined __NR_clock_getres || HP_TIMING_AVAIL
  52     case _SC_CPUTIME:
  53     case _SC_THREAD_CPUTIME:
  54       {
  55         /* If we have HP_TIMING, we will fall back on that if the system
  56            call does not work, so we support it either way.  */
  57 # if !HP_TIMING_AVAIL
  58         /* Check using the clock_getres system call.  */
  59         struct timespec ts;
  60         INTERNAL_SYSCALL_DECL (err);
  61         int r = INTERNAL_SYSCALL (clock_getres, err, 2,
  62                                   (name == _SC_CPUTIME
  63                                    ? CLOCK_PROCESS_CPUTIME_ID
  64                                    : CLOCK_THREAD_CPUTIME_ID),
  65                                   &ts);
  66         if (INTERNAL_SYSCALL_ERROR_P (r, err))
  67           return -1;
  68 # endif
  69         return _POSIX_VERSION;
  70       }
  71 #endif
  72
  73     case _SC_NGROUPS_MAX:
  74       /* Try to read the information from the /proc/sys/kernel/ngroups_max
  75          file.  */
  76       procfname = "/proc/sys/kernel/ngroups_max";
  77       break;
  78
  79     case _SC_SIGQUEUE_MAX:
  80       /* The /proc/sys/kernel/rtsig-max file contains the answer.  */
  81       procfname = "/proc/sys/kernel/rtsig-max";
  82       break;
  83
  84     default:
  85       break;
  86     }
  87
  88   if (procfname != NULL)
  89     {
  90       int fd = open_not_cancel_2 (procfname, O_RDONLY);
  91       if (fd != -1)
  92         {
  93           /* This is more than enough, the file contains a single integer.  */
  94           char buf[32];
  95           ssize_t n;
  96           n = TEMP_FAILURE_RETRY (read_not_cancel (fd, buf, sizeof (buf) - 1));
  97           close_not_cancel_no_status (fd);
  98
  99           if (n > 0)
 100             {
 101               /* Terminate the string.  */
 102               buf[n] = '\0';
 103
 104               char *endp;
 105               long int res = strtol (buf, &endp, 10);
 106               if (endp != buf && (*endp == '\0' || *endp == '\n'))
 107                 return res;
 108             }
 109         }
 110     }
 111
 112   return posix_sysconf (name);
 113 }
 114
 115 /* Now the POSIX version.  */
 116 #undef __sysconf
 117 #define __sysconf static posix_sysconf
 118 #include <sysdeps/posix/sysconf.c>