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SYSCONF(3) BSD Library Functions Manual SYSCONF(3) NAME sysconf -- get configurable system variables LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <unistd.h> long sysconf(int name); DESCRIPTION This interface is defined by IEEE Std 1003.1-1988 ("POSIX.1"). A far more complete interface is available using sysctl(3). The sysconf() function provides a method for applications to determine the current value of a configurable system limit or option variable. The name argument specifies the system variable to be queried. Symbolic con- stants for each name value are found in the include file <unistd.h>. The available values are as follows: _SC_ARG_MAX The maximum bytes of argument to execve(2). _SC_ATEXIT_MAX The maximum number of functions that may be registered with atexit(3). _SC_BARRIERS The version of IEEE Std 1003.1 ("POSIX.1") and its Barriers op- tion to which the system attempts to conform, otherwise -1. _SC_CLOCK_SELECTION Return the POSIX version the implementation of the Clock Selec- tion Option on this system conforms to, or -1 if unavailable. _SC_CHILD_MAX The maximum number of simultaneous processes per user id. _SC_CLK_TCK The number of clock ticks per second. _SC_FSYNC Return 1 if the File Synchronization Option is available on this system, otherwise -1. _SC_HOST_NAME_MAX The maximum size of a hostname, including NULL. _SC_IOV_MAX The maximum number of iovec structures that a process has avail- able for use with preadv(2), pwritev(2), readv(2), recvmsg(2), sendmsg(2) or writev(2). _SC_JOB_CONTROL Return 1 if job control is available on this system, otherwise -1. _SC_LOGIN_NAME_MAX Returns the size of the storage required for a login name, in bytes, including the terminating NUL. _SC_MAPPED_FILES Return 1 if the Memory Mapped Files Option is available on this system, otherwise -1. _SC_MEMLOCK Return 1 if the Process Memory Locking Option is available on this system, otherwise -1. _SC_MEMLOCK_RANGE Return 1 if the Range Memory Locking Option is available on this system, otherwise -1. _SC_MEMORY_PROTECTION Return 1 if the Memory Protection Option is available on this system, otherwise -1. _SC_MONOTONIC_CLOCK Return the POSIX version the implementation of the Monotonic Clock Option on this system conforms to, or -1 if unavailable. _SC_NGROUPS_MAX The maximum number of supplemental groups. _SC_OPEN_MAX The maximum number of open files per process. _SC_PAGESIZE The size of a system page in bytes. _SC_PASS_MAX The maximum length of the password, not counting NULL. _SC_READER_WRITER_LOCKS The version of IEEE Std 1003.1 ("POSIX.1") and its Read-Write Locks option to which the system attempts to conform, otherwise -1. _SC_REGEXP Return 1 if POSIX regular expressions are available on this sys- tem, otherwise -1. _SC_SEMAPHORES The version of IEEE Std 1003.1 ("POSIX.1") and its Semaphores op- tion to which the system attempts to conform, otherwise -1. Availability of the Semaphores option depends on the P1003_1B_SEMAPHORE kernel option. _SC_SHELL Return 1 if POSIX shell is available on this system, otherwise -1. _SC_SPIN_LOCKS The version of IEEE Std 1003.1 ("POSIX.1") and its Spin Locks op- tion to which the system attempts to conform, otherwise -1. _SC_STREAM_MAX The minimum maximum number of streams that a process may have open at any one time. _SC_SYMLOOP_MAX The maximum number of symbolic links that may be expanded in a path name. _SC_SYNCHRONIZED_IO Return 1 if the Synchronized I/O Option is available on this sys- tem, otherwise -1. _SC_THREADS The version of IEEE Std 1003.1 ("POSIX.1") and its Threads option to which the system attempts to conform, otherwise -1. _SC_TIMERS The version of IEEE Std 1003.1 ("POSIX.1") and its Timers option to which the system attempts to conform, otherwise -1. _SC_TZNAME_MAX The minimum maximum number of types supported for the name of a timezone. _SC_SAVED_IDS Returns 1 if saved set-group and saved set-user ID is available, otherwise -1. _SC_VERSION The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply. _SC_XOPEN_SHM Return 1 if the X/Open Portability Guide Issue 4, Version 2 ("XPG4.2") Shared Memory option is available on this system, oth- erwise -1. Availability of the Shared Memory option depends on the SYSVSHM kernel option. _SC_BC_BASE_MAX The maximum ibase/obase values in the bc(1) utility. _SC_BC_DIM_MAX The maximum array size in the bc(1) utility. _SC_BC_SCALE_MAX The maximum scale value in the bc(1) utility. _SC_BC_STRING_MAX The maximum string length in the bc(1) utility. _SC_COLL_WEIGHTS_MAX The maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file. _SC_EXPR_NEST_MAX The maximum number of expressions that can be nested within parenthesis by the expr(1) utility. _SC_LINE_MAX The maximum length in bytes of a text-processing utility's input line. _SC_RE_DUP_MAX The maximum number of repeated occurrences of a regular expres- sion permitted when using interval notation. _SC_2_VERSION The version of POSIX 1003.2 with which the system attempts to comply. _SC_2_C_BIND Return 1 if the system's C-language development facilities sup- port the C-Language Bindings Option, otherwise -1. _SC_2_C_DEV Return 1 if the system supports the C-Language Development Utili- ties Option, otherwise -1. _SC_2_CHAR_TERM Return 1 if the system supports at least one terminal type capa- ble of all operations described in POSIX 1003.2, otherwise -1. _SC_2_FORT_DEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise -1. _SC_2_FORT_RUN Return 1 if the system supports the FORTRAN Runtime Utilities Op- tion, otherwise -1. _SC_2_LOCALEDEF Return 1 if the system supports the creation of locales, other- wise -1. _SC_2_SW_DEV Return 1 if the system supports the Software Development Utili- ties Option, otherwise -1. _SC_2_UPE Return 1 if the system supports the User Portability Utilities Option, otherwise -1. _SC_GETGR_R_SIZE_MAX The minimum size of the buffer passed to getgrgid_r(3) and getgrnam_r(3). _SC_GETPW_R_SIZE_MAX The minimum size of the buffer passed to getpwnam_r(3) and getpwuid_r(3). _SC_NPROCESSORS_CONF The number of processors configured. _SC_NPROCESSORS_ONLN The number of processors online (capable of running processes). RETURN VALUES If the call to sysconf is not successful, -1 is returned and errno is set appropriately. Otherwise, if the variable is associated with functional- ity that is not supported, -1 is returned and errno is not modified. Otherwise, the current variable value is returned. ERRORS The sysconf() function may fail and set errno for any of the errors spec- ified for the library functions sysctl(3). In addition, the following error may be reported: [EINVAL] The value of the name argument is invalid. SEE ALSO getconf(1), limits(3), sysctl(3) STANDARDS The sysconf() function conforms to ISO/IEC 9945-1:1990 ("POSIX.1"). The constants _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are not part of the standard, but are provided by many systems. HISTORY The sysconf function first appeared in 4.4BSD. BUGS The value for _SC_STREAM_MAX is a minimum maximum, and required to be the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously small and misleading number. BSD August 23, 2011 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS
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