sysdeps/unix/sysv/linux/sysconf.c

   1 /* Get file-specific information about a file.  Linux version.
   2    Copyright (C) 2003, 2004 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     case _SC_NGROUPS_MAX:
  52       /* Try to read the information from the /proc/sys/kernel/ngroups_max
  53          file.  */
  54       procfname = "/proc/sys/kernel/ngroups_max";
  55       break;
  56
  57     case _SC_SIGQUEUE_MAX:
  58       /* The /proc/sys/kernel/rtsig-max file contains the answer.  */
  59       procfname = "/proc/sys/kernel/rtsig-max";
  60       break;
  61
  62     default:
  63       break;
  64     }
  65
  66   if (procfname != NULL)
  67     {
  68       int fd = open_not_cancel_2 (procfname, O_RDONLY);
  69       if (fd != -1)
  70         {
  71           /* This is more than enough, the file contains a single integer.  */
  72           char buf[32];
  73           ssize_t n;
  74           n = TEMP_FAILURE_RETRY (read_not_cancel (fd, buf, sizeof (buf) - 1));
  75           close_not_cancel_no_status (fd);
  76
  77           if (n > 0)
  78             {
  79               /* Terminate the string.  */
  80               buf[n] = '\0';
  81
  82               char *endp;
  83               long int res = strtol (buf, &endp, 10);
  84               if (endp != buf && (*endp == '\0' || *endp == '\n'))
  85                 return res;
  86             }
  87         }
  88     }
  89
  90   return posix_sysconf (name);
  91 }
  92
  93 /* Now the POSIX version.  */
  94 #undef __sysconf
  95 #define __sysconf static posix_sysconf
  96 #include <sysdeps/posix/sysconf.c>