sysconf()

Return the value of a configurable system limit

Synopsis:

#include <unistd.h>
#include <limits.h>

long sysconf( int name );

Arguments:

name

The name of the limit that you want to get; see below.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The sysconf() function returns the value of a configurable system limit indicated by name.

Configurable limits are defined in <confname.h>, and contain at least the following values:

_SC_ARG_MAX

Maximum length of arguments for the exec*() functions, in bytes, including environment data.

_SC_CHILD_MAX

Maximum number of simultaneous processes per real user ID.

_SC_CLK_TCK

The number of intervals per second used to express the value in type clock_t.

_SC_NGROUPS_MAX

The maximum number of simultaneous supplementary group IDs per process.

_SC_OPEN_MAX

Maximum number of files that one process can have open at any given time.

_SC_JOB_CONTROL

If this variable is defined, then job control is supported.

_SC_PAGESIZE

The default size of a thread's guard area.

_SC_SAVED_IDS

If this variable is defined, then each process has a saved set-user ID and a saved set-group ID.

_SC_VERSION

The current POSIX version that is currently supported. A value of 198808L indicates the August (08) 1988 standard, as approved by the IEEE Standards Board.

Returns:

The requested configurable system limit. If name isn't defined for the system, -1 is returned.

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <unistd.h>

int main( void )
   {
    printf( "_SC_ARG_MAX = %ld\n",
         sysconf( _SC_ARG_MAX ) );
    return EXIT_SUCCESS;
  }

Classification:

POSIX 1003.1

See also:

confstr(), errno, pathconf()

getconf in the Utilities Reference

Understanding System Limits chapter of the Neutrino User's Guide