sysconf(2) sysconf(2)
NAME [Toc] [Back]
sysconf() - get configurable system variables
SYNOPSIS [Toc] [Back]
#include <unistd.h>
long sysconf(int name);
int CPU_IS_PA_RISC(long cpuvers);
DESCRIPTION [Toc] [Back]
The sysconf() system call provides a way for applications to determine
the current value of a configurable limit or variable.
The name argument represents the system variable being queried.
The following table lists the configuration variable name, the
associated value for the name argument that is used in the sysconf()
call and the value returned:
Variable Value for name Value Returned
_____________________________________________________________________
AES_OS_VERSION _SC_AES_OS_VERSION Version number of OSF/AES
OSC supported
AIO_LISTIO_MAX _SC_AIO_LISTIO_MAX Maximum number of aio
operations that can be
specified in a lio_listio()
call (see lio_listio(2))
AIO_MAX _SC_AIO_MAX Maximum number of aio
operations that can be
queued at any time (see
aio(5))
AIO_PRIO_DELTA_ _SC_AIO_PRIO_ Maximum slowdown factor
MAX DELTA_MAX that can be specified in
the aio_reqprio field of a
aiocb structure (see
aio(5))
ARG_MAX _SC_ARG_MAX Maximum total length of the
arguments for exec() in
bytes, including
environment data (see
exec(2))
ASYNCHRONOUS_IO _SC_ASYNCHRONOUS_IO Not supported
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ATEXIT_MAX _SC_ATEXIT_MAX Maximum number of functions
that can be registered with
atexit() (see atexit(3))
BC_BASE_MAX _SC_BC_BASE_MAX Maximum ibase (input number
radix) and obase (output
number radix) allowed by bc
(see bc(1))
BC_DIM_MAX _SC_BC_DIM_MAX Maximum number of elements
in an array permitted by bc
(see bc(1))
BC_SCALE_MAX _SC_BC_SCALE_MAX Maximum scale factor
(number of digits to the
right of the decimal point)
allowed by bc (see bc(1))
BC_STRING_MAX _SC_BC_STRING_MAX Maximum length of strings
allowed by bc (see bc(1))
CCNUMA_SUPPORT _SC_CCNUMA_SUPPORT Positive if the
implementation supports
multiple locality domains;
-1 otherwise (see mpctl(2))
CHILD_MAX _SC_CHILD_MAX Maximum number of
simultaneous processes per
user ID (see fork(2))
CLK_TCK _SC_CLK_TCK Number of clock intervals
per second for times() (see
times(2))
CLOCKS_PER_SEC _SC_CLOCKS_PER_SEC Number of clock ticks per
second for clock() (see
clock(3C))
COLL_WEIGHTS_ _SC_COLL_ Maximum number of weights
MAX WEIGHTS_MAX that can be assigned to an
entry of the LC_COLLATE
order keyword in a
localedef input file (see
localedef(1M))
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CPU_CHIP_TYPE _SC_CPU_CHIP_TYPE Itanium(R)-based systems:
CPUID Register 3 of the
Itanium-based processor
identification registers.
See the Itanium-based
architecture definition for
this platform for the
meaning of each bit.
CPU_KEYBITS1 _SC_CPU_KEYBITS1 Itanium-based systems:
CPUID Register 4 of the
Itanium-based processor
identification registers.
See the Itanium-based
architecture definition for
this platform for the
meaning of each bit. PA:
Processor Extensions (see
below)
CPU_VERSION _SC_CPU_VERSION Version of CPU architecture
(see below)
DELAYTIMER_MAX _SC_DELAYTIMER_MAX Maximum timer overrun count
EXPR_NEST_MAX _SC_EXPR_NEST_MAX Maximum parenthesis nesting
level for expr expressions
(see expr(1))
GETGR_R_SIZE_MAX _SC_GETGR_R_SIZE_MAX Maximum getgrgid_r(),
getgrnam_r() data buffer
size
GETPW_R_SIZE_MAX _SC_GETPW_R_SIZE_MAX Maximum getpwuid_r(),
getpwnam_r() data buffer
size
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HW_32_64_CAPABLE _SC_HW_32_64_CAPABLE Returns which kernel is
supported on the
hardware. The value
returned is an encoding
which may be
interpreted using the
_SYSTEM_SUPPORTS_ILP32OS()
and
_SYSTEM_SUPPORTS_LP64OS()
macros defined in
unistd.h. Example:
long ret = sysconf(_SC_HW_32_64_CAPABLE);
if (_SYSTEM_SUPPORTS_ILP32OS(ret) != 0) {
/*system supports 32-bit OS*/
}
if (_SYSTEM_SUPPORTS_LP64OS(ret) != 0) {
/*system supports 64-bit OS*/
}
IO_TYPE _SC_IO_TYPE Type of I/O drivers the
kernel supports,
currently, only the
value IO_TYPE_CDIO
KERNEL_BITS _SC_KERNEL_BITS Returns the number of
bits used by the kernel
for pointer and long
data types. Current
values include 32 and
64.
LIBC_VERSION _SC_LIBC_VERSION The version of libc
that is in use by the
application that is
requesting this
information. See below
for details.
LINE_MAX _SC_LINE_MAX Maximum number of bytes
in an input line
(including the newline)
for POSIX.2 utilities
LOGIN_NAME_MAX _SC_LOGIN_NAME_MAX Value of LOGIN_NAME_MAX
MAPPED_FILES _SC_MAPPED_FILES Not supported
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MEMLOCK _SC_MEMLOCK Positive if the system
supports POSIX memory
locking mlockall,
munlockall;
MEMLOCK_RANGE _SC_MEMLOCK_RANGE Positive if the system
supports POSIX memory
range locking;
MEMORY_ _SC_MEMORY_PROTECTION Not supported
PROTECTION
MESSAGE_PASSING _SC_MESSAGE_PASSING Positive if the system
supports POSIX message
queues;
MQ_OPEN_MAX _SC_MQ_OPEN_MAX Maximum number of perprocess
open message
queue descriptors.
MQ_PRIO_MAX _SC_MQ_PRIO_MAX Maximum limit for
message priority.
NGROUPS_MAX _SC_NGROUPS_MAX Maximum number of
simultaneous
supplementary group IDs
per process
OPEN_MAX _SC_OPEN_MAX Maximum number of files
that one process can
have open at one time
PAGE_SIZE _SC_PAGE_SIZE Kernel memory page size
PASS_MAX _SC_PASS_MAX Maximum number of
significant bytes in a
password
POSIX_ _SC_ASYNCHRONOUS_IO Positive if the system
ASYNCHRONOUS_IO supports POSIX
Asynchronous Input and
Output
POSIX_FSYNC _SC_FSYNC Positive if the File
Synchronization option
is supported (see
fsync(2))
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POSIX_JOB_ _SC_JOB_CONTROL Positive if the system
CONTROL supports POSIX job
control; -1 otherwise
POSIX_MAPPED_ _SC_MAPPED_FILES Positive if the system
FILES supports POSIX memory
locking mlockall,
munlockall
POSIX_MEMLOCK _SC_MEMLOCK Positive if the system
supports POSIX memory
mapped files
POSIX_MEMLOCK_ _SC_MEMLOCK_RANGE Positive if the system
RANGE supports POSIX memory
range locking
POSIX_MEMORY_ _SC_MEMORY_PROTECTION Positive if the system
PROTECTION supports POSIX memory
protection
POSIX_MESSAGE_ _SC_MESSAGE_PASSING Positive if the system
PASSING supports POSIX
Prioritized Input and
Output
POSIX_ _SC_PRIORITIZED_IO Positive if the system
PRIORITIZED_IO supports POSIX message
queues;
POSIX_PRIORITY_ _SC_PRIORITY_ Positive if the system
SCHEDULING SCHEDULING supports POSIX.4
priority scheduling -1
otherwise
POSIX_REALTIME_ _SC_REALTIME_ Positive if the system
SIGNALS SIGNALS supports POSIX.4 real
time signal extensions;
-1 otherwise
POSIX_SAVED_IDS _SC_SAVED_IDS Positive if each
process has a saved
set-user-ID and a saved
set-group-ID; -1
otherwise
POSIX_SEMAPHORES _SC_SEMAPHORES Positive if the system
supports POSIX
semaphores
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POSIX_SHARED_ _SC_SHARED_ Positive if the system
MEMORY_OBJECTS MEMORY_OBJECTS supports POSIX shared
memory
POSIX_ _SC_SYNCHRONIZED_IO Positive if the
SYNCHRONIZED_IO Synchronized IO option
is supported (see
open(2))
POSIX_TIMERS _SC_TIMERS Positive if the system
supports POSIX.4 clocks
and timers; -1
otherwise
POSIX_VERSION _SC_VERSION Approval date of the
POSIX.1 Standard (such
as 199009 for POSIX.1-
1990) to which the
system conforms. This
value indicates the
year (first four
digits) and month (next
two digits) that the
standard was approved
by the IEEE Standards
Board.
POSIX_THREAD_ _SC_THREAD_ Positive if the
ATTR_STACKADDR ATTR_STACKADDR implementation supports
the POSIX Thread Stack
Address Attribute
option; -1 otherwise.
POSIX_THREAD_ _SC_THREAD_ Positive if the
ATTR_STACKSIZE ATTR_STACKSIZE implementation supports
the POSIX Thread Stack
Size Attribute option;
-1 otherwise.
POSIX_THREAD_ _SC_THREAD_ Positive if the
PRIORITY_ PRIORITY_SCHEDULING implementation supports
SCHEDULING the POSIX Thread
Priority Scheduling
option; -1 otherwise.
POSIX_THREAD_ _SC_THREAD_ Positive if the
PRIO_INHERIT PRIO_INHERIT implementation supports
the POSIX Thread
Priority Inheritance
option; -1 otherwise.
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POSIX_THREAD_ _SC_THREAD_ Positive if the
PRIO_PROTECT PRIO_PROTECT implementation supports
the POSIX Thread
Priority Protection
option; -1 otherwise.
POSIX_THREAD_ _SC_THREAD_PROCESS_ Positive if the
PROCESS_SHARED SHARED implementation supports
the POSIX Thread
Process-Shared
Synchronization option;
-1 otherwise.
POSIX_THREAD_ _SC_THREAD_SAFE_ Positive if the
SAFE_FUNCTIONS FUNCTIONS implementation supports
the POSIX Thread
Thread-Safe Functions
option; -1 otherwise.
POSIX_THREADS _SC_THREADS Positive if the
implementation supports
POSIX threads; -1
otherwise.
POSIX_TTY_ _SC_TTY_NAME_MAX Maximum length of a
NAME_MAX terminal device name
POSIX2_C_BIND _SC_2_C_BIND Equal to 1 if the
POSIX.2 C Language
Bindings Option is
available through the
c89 utility; -1
otherwise
POSIX2_C_DEV _SC_2_C_DEV Equal to 1 if the
POSIX.2 C Language
Development Utilities
Option is supported; -1
otherwise
POSIX2_C_VERSION _SC_2_C_VERSION Current version of the
POSIX.2 C Language
Binding Option
supported (same format
as _POSIX_VERSION); -1
otherwise.
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POSIX2_FORT_DEV _SC_2_FORT_DEV Equal to 1 if the
POSIX.2 FORTRAN
Development Utilities
Option is supported; -1
otherwise
POSIX2_FORT_RUN _SC_2_FORT_RUN Equal to 1 if the
POSIX.2 Fortran Runtime
Utilities Option is
supported; -1 otherwise
POSIX2_LOCALEDEF _SC_2_LOCALEDEF Equal to 1 if locales
can be created with the
POSIX.2 localedef
utility; -1 otherwise
POSIX2_SW_DEV _SC_2_SW_DEV Equal to 1 if the
POSIX.2 Software
Development Utilities
Option is supported; -1
otherwise
POSIX2_UPE _SC_2_UPE Equal to 1 if the
POSIX.2 User
Portability Utilities
Option is supported; -1
otherwise
POSIX2_VERSION _SC_2_VERSION Current version of
POSIX.2 (same format as
_POSIX_VERSION)
PRIORITIZED_IO _SC_PRIORITIZED_IO Not supported
PROCESSOR_SET _SC_PSET_SUPPORT Positive if the
implementation supports
the Processor Set
Functions; -1
otherwise.
PTHREAD_ _SC_THREAD_ The number of attempts
DESTRUCTOR_ DESTRUCTOR_ made to destroy a
ITERATIONS ITERATIONS pthread's threadspecific
data values on
thread exit.
PTHREAD_KEYS_MAX _SC_THREAD_ The number of pthread
KEYS_MAX data keys per process.
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PTHREAD_STACK_ _SC_THREAD_ Minimum size in bytes
MIN STACK_MIN of pthread stack
storage.
PTHREAD_THREADS_ _SC_THREAD_ Maximum number of
MAX THREADS_MAX pthreads that can be
created per process.
PROC_RSRC_MGR _SC_PROC_RSRC_MGR Equal to 1 if the
optional HP Process
Resource Management
(PRM) software is
installed and
configured; 0 otherwise
(see prmconfig(1))
RE_DUP_MAX _SC_RE_DUP_MAX Maximum number of
repeated occurrences of
a regular expression
permitted when using
the interval notation
\{m,n\} (see
regcomp(3C))
RTSIG_MAX _SC_RTSIG_MAX Maximum number of
realtime signals
reserved for
application use.
SECURITY_CLASS _SC_SECURITY_CLASS SEC_CLASS-NONE (No DoD
security level
supported)
SEMAPHORES _SC_SEMAPHORES Positive if the system
supports POSIX
semaphores
SEM_NSEMS_MAX _SC_SEM_NSEMS_MAX Maximum number of open
semaphores per process
SEM_VALUE_MAX _SC_SEM_VALUE_MAX Maximum semaphore value
SHARED_MEMORY_ _SC_SHARED_MEMORY_ Positive if the system
OBJECTS OBJECTS supports POSIX shared
memory
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SIGQUEUE_MAX _SC_SIGQUEUE_MAX Maximum number of
queued signals that a
process may send and
have pending at the
receiver(s) at any
time.
STREAM_MAX _SC_STREAM_MAX Maximum number of stdio
streams that one
process can have open
at one time
TIMER_MAX _SC_TIMER_MAX Maximum number of
POSIX.4 timers per
process, if POSIX.4
timers are supported;
-1 otherwise
TTY_NAME_MAX _SC_TTY_NAME_MAX Value of TTY_NAME_MAX
TZNAME_MAX _SC_TZNAME_MAX Maximum number of bytes
in a time zone name for
the TZ environment
variable
XOPEN_CRYPT _SC_XOPEN_CRYPT Equal to 1 if the
X/Open Encryption
Feature Group is
supported; -1 otherwise
XOPEN_ENH_I18N _SC_XOPEN_ENH_I18N Equal to 1 if the
X/Open Enhanced
Internationalization
Feature Group is
supported; -1
otherwise.
XOPEN_SHM _SC_XOPEN_SHM Equal to 1 if the
X/Open Shared Memory
Feature Group is
supported; -1 otherwise
XOPEN_VERSION _SC_XOPEN_VERSION Issue number of X/Open
Portability Guide
supported
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XBS5_ILP32_ _SC_XBS5_ILP32_ A flag which denotes
OFF32 OFF32 whether
_CS_XBS5_ILP32_OFF32_CFLAGS,
_CS_XBS5_ILP32_OFF32_LDFLAGS,
_CS_XBS5_ILP32_OFF32_LIBS
and
_CS_XBS5_ILP32_OFF32_LINTFLAGS
are supported by
confstr(3C). A return
value of -1 indicates
they are not supported.
XBS5_ILP32_ _SC_XBS5_ILP32_ A flag which denotes
OFFBIG OFFBIG whether
_CS_XBS5_ILP32_OFFBIG_CFLAGS,
_CS_XBS5_ILP32_OFFBIG_LDFLAGS,
_CS_XBS5_ILP32_OFFBIG_LIBS
and
_CS_XBS5_ILP32_OFFBIG_LINTFLAGS
are supported by
confstr(3C). A return
value of -1 indicates
they are not supported.
XBS5_LP64_ _SC_XBS5_LP64_ A flag which denotes
OFF64 OFF64 whether
_CS_XBS5_LP64_OFF64_CFLAGS,
_CS_XBS5_LP64_OFF64_LDFLAGS,
_CS_XBS5_LP64_OFF64_LIBS
and
_CS_XBS5_LP64_OFF64_LINTFLAGS
are supported by
confstr(3C). A return
value of -1 indicates
they are not supported.
XBS5_LPBIG_ _SC_XBS5_LPBIG_ A flag which denotes
OFFBIG OFFBIG whether
_CS_XBS5_LPBIG_OFFBIG_CFLAGS,
_CS_XBS5_LPBIG_OFFBIG_LDFLAGS,
_CS_XBS5_LPBIG_OFFBIG_LIBS
and
_CS_XBS5_LPBIG_OFFBIG_LINTFLAGS
are supported by
confstr(3C). A return
value of -1 indicates
they are not supported.
_______________________________________________________________________
Some of the variables in the table are defined as constants in
<limits.h> (see limits(5)). The associated values of the name
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argument are defined in <unistd.h>.
The possible values of the CPU_VERSION variable returned by
sysconf(_SC_CPU_VERSION) and their meanings are:
Value Meaning
_______________________________________________________________
CPU_PA_RISC1_0 HP Precision Architecture RISC Version 1.0
CPU_PA_RISC1_1 HP Precision Architecture RISC Version 1.1
CPU_PA_RISC2_0 HP Precision Architecture RISC Version 2.0
CPU_IA64_ARCHREV_0 HP Itanium-based Architecture Version 0
The CPU_IS_PA_RISC() function classifies cpuvers, a value of the
CPU_VERSION variable, as to its processor family.
The availability of architecture specific instructions is indicated by
the key bit data returned by sysconf(_SC_CPU_KEYBITS1). Upon
successful completion, the data returned will be the logical OR of the
defined values for the features supported.
The possible values returned by sysconf(_SC_CPU_KEYBITS1) and their
meanings for PA platforms are shown in the following table.
Return Value Instruction Supported
______________________________________________________________
HARITH Halfword parallel add, subtract, and average
HSHIFT Halfword parallel shift-and-add
The format of the value returned by sysconf(_SC_LIBC_VERSION) is as
follows:
XXyyZZZZqN
where
XX HP-UX major release number
yy HP-UX minor release number
ZZZZ Library-specific number
q 0=32PA 1=64PA 2=32EM 3=64EM 4-9=Reserved
N 0 = archive library
1-9 = System V version of shared library
RETURN VALUE [Toc] [Back]
Upon successful completion, sysconf() returns the value of the named
variable. If the value of name is not recognized, sysconf() returns
-1 and sets errno to [EINVAL]. If the value in name is defined but is
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not supported in this environment, sysconf() returns -1, but does not
change errno.
CPU_IS_PA_RISC() returns positive nonzero if cpuvers is an HP PA-RISC
processor; zero if not.
ERRORS [Toc] [Back]
If sysconf() fails, the value of errno (see errno(2)) is set to:
[EINVAL] The value of name is not valid.
EXAMPLES [Toc] [Back]
The following example determines the number of times the system clock
ticks each second:
#include <unistd.h>
long ticks;
...
ticks = sysconf(_SC_CLK_TCK);
The following example determines if the current processor is an HP
PA-RISC machine:
#include <unistd.h>
if (CPU_IS_PA_RISC(sysconf(_SC_CPU_VERSION)))
...
WARNINGS [Toc] [Back]
CPU_IS_PA_RISC() is implemented as a macro.
Normally, the values returned from sysconf() do not change during the
lifetime of the calling process. However, the value of the symbolic
constant _POSIX_VERSION and thus the value of sysconf(_SC_VERSION) can
vary under certain circumstances. If either of the feature test
macros _POSIX1_1988 or _XPG3 is defined by the programmer prior to
including <unistd.h>, the value of _POSIX_VERSION is defined as
198808, in conformance with POSIX.1-1988, FIPS 151-1, and XPG3.
Otherwise, the value of _POSIX_VERSION is defined as 199009, in
conformance with POSIX.1-1990.
Similarly, the value of the symbolic constant _XOPEN_VERSION and thus
the value of sysconf(_SC_XOPEN_VERSION) can vary under certain
circumstances. If the feature test macro _XPG3 is defined by the
programmer prior to including <unistd.h>, the value of _XOPEN_VERSION
is defined as 3, in conformance with XPG3. Otherwise, the value of
_XOPEN_VERSION is defined as 4, in conformance with XPG4.
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See stdsyms(5) for more information about these feature test macros.
Any application that has a dependency on libdld.sl is a potential user
of both archived and shared libc. Applications that comprise both
archived and shared components where sysconf(_SC_LIBC_VERSION) may be
invoked from both the archived and shared components may get
inconsistent return values from sysconf().
AUTHOR [Toc] [Back]
sysconf() was developed by HP and POSIX.
CPU_IS_PA_RISC() was developed by HP.
SEE ALSO [Toc] [Back]
getconf(1), exec(2), fork(2), getrlimit(2), pathconf(2), times(2),
atexit(3), clock(3C), regcomp(3C), limits(5), stdsyms(5),
thread_safety(5), unistd(5).
HP Process Resource Manager: prmconfig(1) in HP Process Resource
Manager User's Guide.
STANDARDS CONFORMANCE [Toc] [Back]
sysconf(): AES, SVID3, XPG3, XPG4, FIPS 151-2, POSIX.1, POSIX.2,
POSIX.4
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