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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_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

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes