sysconf.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <sys/param.h>
#include    <errno.h>
#include    <limits.h>
#include    <unistd.h>

long
sysconf(int name)
{
    switch (name) {
    case _SC_ARG_MAX:    return(ARG_MAX);
    case _SC_CHILD_MAX:    return(CHILD_MAX);
    case _SC_CLK_TCK:    return(CLK_TCK);
    case _SC_NGROUPS_MAX:    return(NGROUPS_MAX);
    case _SC_OPEN_MAX:    return(OPEN_MAX);
        /* Could actually call getdtablesize() or getrlimit(),
           since OPEN_MAX isn't really the limit */
    case _SC_VERSION:    return(_POSIX_VERSION);

    case _SC_JOB_CONTROL:
#ifdef    _POSIX_JOB_CONTROL    /* always true for BSD */
        return(1);
#else
        return(-1);
#endif

    case _SC_SAVED_IDS:
#ifdef    _POSIX_SAVED_IDS    /* not true yet for BSD */
        return(1);
#else
        return(-1);
#endif

    default:    
        errno = EINVAL;
        return(-1);
    }
}