sysconf(3C) C Library Functions sysconf(3C) NAME sysconf - get configurable system variables SYNOPSIS #include long sysconf(int _n_a_m_e); MT-LEVEL MT-Safe, Async-Signal-Safe DESCRIPTION The sysconf() function provides a method for an application to determine the current value of a configurable system limit or option (variable). The _n_a_m_e argument represents the system variable to be queried. The following table lists the minimal set of sys- tem variables from and that can be returned by sysconf(), and the symbolic constants, defined in that are the corresponding values used for _n_a_m_e. _N_a_m_e _R_e_t_u_r_n _V_a_l_u_e _M_e_a_n_i_n_g _SC_ARG_MAX ARG_MAX Max size of argv[] plus envp[]. _SC_CHILD_MAX CHILD_MAX Max processes allowed to a UID. _SC_CLK_TCK CLK_TCK Ticks per second (clock_t). _SC_NGROUPS_MAX NGROUPS_MAX Max simultaneous groups to which one may belong. _SC_OPEN_MAX OPEN_MAX Max open files per process. _SC_PASS_MAX PASS_MAX _SC_PAGESIZE PAGESIZE System memory page size. _SC_JOB_CONTROL _POSIX_JOB_CONTROL Job control supported? _SC_SAVED_IDS _POSIX_SAVED_IDS Saved IDs (seteuid()) supported? _SC_VERSION _POSIX_VERSION POSIX.1 version supported. _SC_XOPEN_VERSION _XOPEN_VERSION _SC_LOGNAME_MAX LOGNAME_MAX _SC_NPROCESSORS_CONF Number of processors configured. _SC_NPROCESSORS_ONLN Number of processors online. _SC_PHYS_PAGES Total number of pages of physical memory in system. _SC_AVPHYS_PAGES Number physical memory pages not currently in use by system. _SC_AIO_LISTIO_MAX AIO_LISTIO_MAX Max number of I/O operations in a single list I/O call supported by implementation. _SC_AIO_MAX AIO_MAX Max number of outstanding asynchronous I/O operations supported by implementation. _SC_AIO_PRIO_DELTA_MAX AIO_PRIO_DELTA_MAX Max amount by which a process can decrease its asynchronous /O priority level from its own SunOS 5.5 Last change: 20 Sep 1995 1 sysconf(3C) C Library Functions sysconf(3C) scheduling priority. _SC_DELAYTIMER_MAX DELAYTIMER_MAX Max number of timer expiration overruns. _SC_GETGR_R_SIZE_MAX NSS_BUFLEN_GROUP Max size of group entry buffer. _SC_GETPW_R_SIZE_MAX NSS_BUFLEN_PASSWD Max size of password entry buffer. _SC_LOGIN_NAME_MAX LOGNAME_MAX + 1 Max length of login name. _SC_MQ_OPEN_MAX MQ_OPEN_MAX Max number of open message queues a process may hold. _SC_MQ_PRIO_MAX MQ_PRIO_MAX Max number of message priorities supported by implementation. _SC_RTSIG_MAX RTSIG_MAX Max number of realtime signals reserved for application use in this implementation. _SC_SEM_NSEMS_MAX SEM_NSEMS_MAX Max number of semaphores that a process may have. _SC_SEM_VALUE_MAX SEM_VALUE_MAX Max value a semaphore may have. _SC_SIGQUEUE_MAX SIGQUEUE_MAX Max number of queued signals that a process may send and have pending at receiver(s) at a time. _SC_TIMER_MAX TIMER_MAX Max number of timers per process supported by implementation. _SC_ASYNCHRONOUS_IO _POSIX_ASYNCHRONOUS_IO Supports Asynchronous I/O. _SC_FSYNC _POSIX_FSYNC Supports File Synchronization. _SC_MAPPED_FILES _POSIX_MAPPED_FILES Supports Memory Mapped Files. _SC_MEMLOCK _POSIX_MEMLOCK Supports Process Memory Locking. _SC_MEMLOCK_RANGE _POSIX_MEMLOCK_RANGE Supports Range Memory Locking. _SC_MEMORY_PROTECTION _POSIX_MEMORY_PROTECTION Supports Memory Protection. _SC_MESSAGE_PASSING _POSIX_MESSAGE_PASSING Supports Message Passing. _SC_PRIORITIZED_IO _POSIX_PRIORITIZED_IO Supports Prioritized I/O. _SC_PRIORITY_SCHEDULING _POSIX_PRIORITY_SCHEDULING Supports Process Scheduling _SC_REALTIME_SIGNALS _POSIX_REALTIME_SIGNALS Supports Realtime Signals. _SC_SEMAPHORES _POSIX_SEMAPHORES Supports Semaphores. _SC_SHARED_MEMORY_ _POSIX_SHARED_MEMORY_ Supports Shared Memory OBJECTS OBJECTS Objects. _SC_SYNCHRONIZED_IO _POSIX_SYNCHRONIZED_IO Supports Synchronized I/O. _SC_TIMERS _POSIX_TIMERS Supports Timers. _SC_THREAD_DESTRUCTOR_ PTHREAD_DESTRUCTOR_ Number attempts made to destroy ITERATIONS ITERATIONS thread-specific data on thread exit. _SC_THREAD_KEYS_MAX PTHREAD_KEYS_MAX Max number of data keys per process. _SC_THREAD_STACK_MIN PTHREAD_STACK_MIN Min byte size of thread stack storage. _SC_THREAD_THREADS_MAX PTHREAD_THREADS_MAX Max number of threads per process. _SC_TTY_NAME_MAX TTYNAME_MAX Max length of tty device name. _SC_THREADS _POSIX_THREADS Supports Threads option. _SC_THREAD_ATTR_STACKADDR _POSIX_THREAD_ATTR_STACKADDR Supports Thread Stack Address Attribute option. _SC_THREAD_ATTR_STACKSIZE _POSIX_THREAD_ATTR_STACKSIZE Supports Thread Stack Size Attribute option. _SC_THREAD_PRIORITY_SCHEDULING _POSIX_THREAD_PRIORITY_SCHEDULING Supports Thread Execution Scheduling option. _SC_THREAD_PRIO_INHERIT _POSIX_THREAD_PRIO_INHERIT SunOS 5.5 Last change: 20 Sep 1995 2 sysconf(3C) C Library Functions sysconf(3C) Supports Priority Inheritance option. _SC_THREAD_PRIO_PROTECT _POSIX_THREAD_PRIO_PROTECT Supports Priority Protection option. _SC_THREAD_PROCESS_SHARED _POSIX_THREAD_PROCESS_SHARED Supports Process-Shared Synchronization option. _SC_THREAD_SAFE_FUNCTIONS _POSIX_THREAD_SAFE_FUNCTIONS Supports Thread-Safe Functions option. RETURN VALUES If _n_a_m_e is an invalid value, sysconf() will return - 1 and set errno to indicate the error. If sysconf() fails due to a value of _n_a_m_e that is not defined on the system, the func- tion will return a value of -1 without changing the value of errno. SEE ALSO fpathconf(2), seteuid(2), setrlimit(2) NOTES A call to setrlimit() may cause the value of OPEN_MAX to change. Multiplying _SC_PHYS_PAGES or _SC_AVPHYS_PAGES by _SC_PAGESIZE to determine memory amount in bytes can exceed the maximum values representable in a long or unsigned long. _SC_PHYS_PAGES and _SC_AVPHYS_PAGES are specific to Solaris 2.3 and later releases. The value of CLK_TCK may be variable and it should not be assumed that CLK_TCK is a compile-time constant. Calling sysconf() with _SC_THREAD_KEYS_MAX or _SC_THREAD_THREADS_MAX returns -1, because no maximum limit can be determined. The system supports at least the minimum values defined by _POSIX_THREAD_KEYS_MAX and _POSIX_THREAD_THREADS_MAX and can support higher values depending upon system resources. _SC_THREAD_PRIO_INHERIT and _SC_THREAD_PRIO_PROTECT are currently not supported, so sysconf() with these arguments returns -1. SunOS 5.5 Last change: 20 Sep 1995 3