NAME
sysconf - get configurable system variables
SYNOPSIS
#include
long sysconf(int name);
DESCRIPTION
The sysconf() function provides a method for the application to determine the current value of a configurable system limit or option ( variable). The implementation shall support all of the variables listed in the following table and may support others.
The name argument represents the system variable to be queried. The following table lists the minimal set of system variables from or that can be returned by sysconf(), and the symbolic constants defined in that are the corresponding values used for name.
Variable
Value of Name
{AIO_LISTIO_MAX}
_SC_AIO_LISTIO_MAX
{AIO_MAX}
_SC_AIO_MAX
{AIO_PRIO_DELTA_MAX}
_SC_AIO_PRIO_DELTA_MAX
{ARG_MAX}
_SC_ARG_MAX
{ATEXIT_MAX}
_SC_ATEXIT_MAX
{BC_BASE_MAX}
_SC_BC_BASE_MAX
{BC_DIM_MAX}
_SC_BC_DIM_MAX
{BC_SCALE_MAX}
_SC_BC_SCALE_MAX
{BC_STRING_MAX}
_SC_BC_STRING_MAX
{CHILD_MAX}
_SC_CHILD_MAX
Clock ticks/second
_SC_CLK_TCK
{COLL_WEIGHTS_MAX}
_SC_COLL_WEIGHTS_MAX
{DELAYTIMER_MAX}
_SC_DELAYTIMER_MAX
{EXPR_NEST_MAX}
_SC_EXPR_NEST_MAX
{HOST_NAME_MAX}
_SC_HOST_NAME_MAX
{IOV_MAX}
_SC_IOV_MAX
{LINE_MAX}
_SC_LINE_MAX
{LOGIN_NAME_MAX}
_SC_LOGIN_NAME_MAX
{NGROUPS_MAX}
_SC_NGROUPS_MAX
Maximum size of getgrgid_r() and
_SC_GETGR_R_SIZE_MAX
getgrnam_r() data buffers
Maximum size of getpwuid_r() and
_SC_GETPW_R_SIZE_MAX
RETURN VALUE
If name is an invalid value, sysconf() shall return -1 and set errno to indicate the error. If the variable corresponding to name has no limit, sysconf() shall return -1 without changing the value of errno. Note that indefinite limits do not imply infinite limits; see .
Otherwise, sysconf() shall return the current variable value on the system. The value returned shall not be more restrictive than the corresponding value described to the application when it was compiled with the implementation's or . The value shall not change during the lifetime of the calling process, [XSI] except that sysconf(_SC_OPEN_MAX) may return different values before and after a call to setrlimit() which changes the RLIMIT_NOFILE soft limit.
If the variable corresponding to name is dependent on an unsupported option, the results are unspecified.
ERRORS
The sysconf() function shall fail if:
[EINVAL]
The value of the name argument is invalid.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
As -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno to 0, then call sysconf(), and, if it returns -1, check to see if errno is non-zero.
Application writers should check whether an option, such as _POSIX_TRACE, is supported prior to obtaining and using values for related variables, such as _POSIX_TRACE_NAME_MAX.
RATIONALE
This functionality was added in response to requirements of application developers and of system vendors who deal with many international system configurations. It is closely related to pathconf() and fpathconf().
Although a conforming application can run on all systems by never demanding more resources than the minimum values published in this volume of IEEE Std 1003.1-2001, it is useful for that application to be able to use the actual value for the quantity of a resource available on any given system. To do this, the application makes use of the value of a symbolic constant in or .
However, once compiled, the application must still be able to cope if the amount of resource available is increased. To that end, an application may need a means of determining the quantity of a resource, or the presence of an option, at execution time.
Two examples are offered:
Applications may wish to act differently on systems with or without job control. Applications vendors who wish to distribute only a single binary package to all instances of a computer architecture would be forced to assume job control is never available if it were to rely solely on the value published in this volume of IEEE Std 1003.1-2001.
International applications vendors occasionally require knowledge of the number of clock ticks per second. Without these facilities, they would be required to either distribute their applications partially in source form or to have 50 Hz and 60 Hz versions for the various countries in which they operate.
It is the knowledge that many applications are actually distributed widely in executable form that leads to this facility. If limited to the most restrictive values in the headers, such applications would have to be prepared to accept the most limited environments offered by the smallest microcomputers. Although this is entirely portable, there was a consensus that they should be able to take advantage of the facilities offered by large systems, without the restrictions associated with source and object distributions.
During the discussions of this feature, it was pointed out that it is almost always possible for an application to discern what a value might be at runtime by suitably testing the various functions themselves. And, in any event, it could always be written to adequately deal with error returns from the various functions. In the end, it was felt that this imposed an unreasonable level of complication and sophistication on the application writer.
This runtime facility is not meant to provide ever-changing values that applications have to check multiple times. The values are seen as changing no more frequently than once per system initialization, such as by a system administrator or operator with an automatic configuration program. This volume of IEEE Std 1003.1-2001 specifies that they shall not change within the lifetime of the process.
Some values apply to the system overall and others vary at the file system or directory level. The latter are described in pathconf().
Note that all values returned must be expressible as integers. String values were considered, but the additional flexibility of this approach was rejected due to its added complexity of implementation and use.
Some values, such as {PATH_MAX}, are sometimes so large that they must not be used to, say, allocate arrays. The sysconf() function returns a negative value to show that this symbolic constant is not even defined in this case.
Similar to pathconf(), this permits the implementation not to have a limit. When one resource is infinite, returning an error indicating that some other resource limit has been reached is conforming behavior.
FUTURE DIRECTIONS
None.
SEE ALSO
confstr(), pathconf(), the Base Definitions volume of IEEE Std 1003.1-2001, , , the Shell and Utilities volume of IEEE Std 1003.1-2001, getconf
CHANGE HISTORY
First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.
Issue 5
The DESCRIPTION is updated for alignment with the POSIX Realtime Extension and the POSIX Threads Extension.
The _XBS_ variables and name values are added to the table of system variables in the DESCRIPTION. These are all marked EX.
Issue 6
The symbol CLK_TCK is obsolescent and removed. It is replaced with the phrase "clock ticks per second".
The symbol {PASS_MAX} is removed.
The following changes were made to align with the IEEE P1003.1a draft standard:
Table entries are added for the following variables: _SC_REGEXP, _SC_SHELL, _SC_REGEX_VERSION, _SC_SYMLOOP_MAX.
The following sysconf() variables and their associated names are added for alignment with IEEE Std 1003.1d-1999:
The macros associated with the c89 programming models are marked LEGACY, and new equivalent macros associated with c99 are introduced.
IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/62 is applied, updating the DESCRIPTION to denote that the _PC* and _SC* symbols are now required to be supported. A corresponding change has been made in the Base Definitions volume of IEEE Std 1003.1-2001. The deletion in the second paragraph removes some duplicated text. Additional symbols that were erroneously omitted from this reference page have been added.
IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/63 is applied, making it clear in the RETURN VALUE section that the value returned for sysconf(_SC_OPEN_MAX) may change if a call to setrlimit() adjusts the RLIMIT_NOFILE soft limit.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/134 is applied, updating the DESCRIPTION to remove an erroneous entry for _POSIX_SYMLOOP_MAX. This corrects an error in IEEE Std 1003.1-2001/Cor 1-2002.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/135 is applied, removing _POSIX_FILE_LOCKING, _POSIX_MULTI_PROCESS, _POSIX2_C_VERSION, and _XOPEN_XCU_VERSION (and their associated _SC_* variables) from the DESCRIPTION and APPLICATION USAGE sections.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/136 is applied, adding _POSIX_SS_REPL_MAX, _POSIX_TRACE_EVENT_NAME_MAX, _POSIX_TRACE_NAME_MAX, _POSIX_TRACE_SYS_MAX, and _POSIX_TRACE_USER_EVENT_MAX (and their associated _SC_* variables) to the DESCRIPTION. The RETURN VALUE and APPLICATION USAGE sections are updated to note that if variables are dependent on unsupported options, the results are unspecified.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/137 is applied, removing _REGEX_VERSION and _SC_REGEX_VERSION.
UNIX ® is a registered Trademark of The Open Group.
POSIX ® is a registered Trademark of The IEEE.
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dengwei19890716 于 2009-10-21 12:46:31发表:
The Open Group Base Specifications Issue 6
or that can be returned by sysconf(), and the symbolic constants defined in that are the corresponding values used for name.
.
or . The value shall not change during the lifetime of the calling process, [XSI] except that sysconf(_SC_OPEN_MAX) may return different values before and after a call to setrlimit() which changes the RLIMIT_NOFILE soft limit.
or .
value published in this volume of IEEE Std 1003.1-2001.
, , the Shell and Utilities volume of IEEE Std 1003.1-2001, getconf
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
--------------------------------------------------------------------------------
NAME
sysconf - get configurable system variables
SYNOPSIS
#include
long sysconf(int name);
DESCRIPTION
The sysconf() function provides a method for the application to determine the current value of a configurable system limit or option ( variable). The implementation shall support all of the variables listed in the following table and may support others.
The name argument represents the system variable to be queried. The following table lists the minimal set of system variables from
Variable
Value of Name
{AIO_LISTIO_MAX}
_SC_AIO_LISTIO_MAX
{AIO_MAX}
_SC_AIO_MAX
{AIO_PRIO_DELTA_MAX}
_SC_AIO_PRIO_DELTA_MAX
{ARG_MAX}
_SC_ARG_MAX
{ATEXIT_MAX}
_SC_ATEXIT_MAX
{BC_BASE_MAX}
_SC_BC_BASE_MAX
{BC_DIM_MAX}
_SC_BC_DIM_MAX
{BC_SCALE_MAX}
_SC_BC_SCALE_MAX
{BC_STRING_MAX}
_SC_BC_STRING_MAX
{CHILD_MAX}
_SC_CHILD_MAX
Clock ticks/second
_SC_CLK_TCK
{COLL_WEIGHTS_MAX}
_SC_COLL_WEIGHTS_MAX
{DELAYTIMER_MAX}
_SC_DELAYTIMER_MAX
{EXPR_NEST_MAX}
_SC_EXPR_NEST_MAX
{HOST_NAME_MAX}
_SC_HOST_NAME_MAX
{IOV_MAX}
_SC_IOV_MAX
{LINE_MAX}
_SC_LINE_MAX
{LOGIN_NAME_MAX}
_SC_LOGIN_NAME_MAX
{NGROUPS_MAX}
_SC_NGROUPS_MAX
Maximum size of getgrgid_r() and
_SC_GETGR_R_SIZE_MAX
getgrnam_r() data buffers
Maximum size of getpwuid_r() and
_SC_GETPW_R_SIZE_MAX
getpwnam_r() data buffers
{MQ_OPEN_MAX}
_SC_MQ_OPEN_MAX
{MQ_PRIO_MAX}
_SC_MQ_PRIO_MAX
{OPEN_MAX}
_SC_OPEN_MAX
_POSIX_ADVISORY_INFO
_SC_ADVISORY_INFO
_POSIX_BARRIERS
_SC_BARRIERS
_POSIX_ASYNCHRONOUS_IO
_SC_ASYNCHRONOUS_IO
_POSIX_CLOCK_SELECTION
_SC_CLOCK_SELECTION
_POSIX_CPUTIME
_SC_CPUTIME
_POSIX_FSYNC
_SC_FSYNC
_POSIX_IPV6
_SC_IPV6
_POSIX_JOB_CONTROL
_SC_JOB_CONTROL
_POSIX_MAPPED_FILES
_SC_MAPPED_FILES
_POSIX_MEMLOCK
_SC_MEMLOCK
_POSIX_MEMLOCK_RANGE
_SC_MEMLOCK_RANGE
_POSIX_MEMORY_PROTECTION
_SC_MEMORY_PROTECTION
_POSIX_MESSAGE_PASSING
_SC_MESSAGE_PASSING
_POSIX_MONOTONIC_CLOCK
_SC_MONOTONIC_CLOCK
_POSIX_PRIORITIZED_IO
_SC_PRIORITIZED_IO
_POSIX_PRIORITY_SCHEDULING
_SC_PRIORITY_SCHEDULING
_POSIX_RAW_SOCKETS
_SC_RAW_SOCKETS
_POSIX_READER_WRITER_LOCKS
_SC_READER_WRITER_LOCKS
_POSIX_REALTIME_SIGNALS
_SC_REALTIME_SIGNALS
_POSIX_REGEXP
_SC_REGEXP
_POSIX_SAVED_IDS
_SC_SAVED_IDS
_POSIX_SEMAPHORES
_SC_SEMAPHORES
_POSIX_SHARED_MEMORY_OBJECTS
_SC_SHARED_MEMORY_OBJECTS
_POSIX_SHELL
_SC_SHELL
_POSIX_SPAWN
_SC_SPAWN
_POSIX_SPIN_LOCKS
_SC_SPIN_LOCKS
_POSIX_SPORADIC_SERVER
_SC_SPORADIC_SERVER
_POSIX_SS_REPL_MAX
_SC_SS_REPL_MAX
_POSIX_SYNCHRONIZED_IO
_SC_SYNCHRONIZED_IO
_POSIX_THREAD_ATTR_STACKADDR
_SC_THREAD_ATTR_STACKADDR
_POSIX_THREAD_ATTR_STACKSIZE
_SC_THREAD_ATTR_STACKSIZE
_POSIX_THREAD_CPUTIME
_SC_THREAD_CPUTIME
_POSIX_THREAD_PRIO_INHERIT
_SC_THREAD_PRIO_INHERIT
_POSIX_THREAD_PRIO_PROTECT
_SC_THREAD_PRIO_PROTECT
_POSIX_THREAD_PRIORITY_SCHEDULING
_SC_THREAD_PRIORITY_SCHEDULING
_POSIX_THREAD_PROCESS_SHARED
_SC_THREAD_PROCESS_SHARED
_POSIX_THREAD_SAFE_FUNCTIONS
_SC_THREAD_SAFE_FUNCTIONS
_POSIX_THREAD_SPORADIC_SERVER
_SC_THREAD_SPORADIC_SERVER
_POSIX_THREADS
_SC_THREADS
_POSIX_TIMEOUTS
_SC_TIMEOUTS
_POSIX_TIMERS
_SC_TIMERS
_POSIX_TRACE
_SC_TRACE
_POSIX_TRACE_EVENT_FILTER
_SC_TRACE_EVENT_FILTER
_POSIX_TRACE_EVENT_NAME_MAX
_SC_TRACE_EVENT_NAME_MAX
_POSIX_TRACE_INHERIT
_SC_TRACE_INHERIT
_POSIX_TRACE_LOG
_SC_TRACE_LOG
_POSIX_TRACE_NAME_MAX
_SC_TRACE_NAME_MAX
_POSIX_TRACE_SYS_MAX
_SC_TRACE_SYS_MAX
_POSIX_TRACE_USER_EVENT_MAX
_SC_TRACE_USER_EVENT_MAX
_POSIX_TYPED_MEMORY_OBJECTS
_SC_TYPED_MEMORY_OBJECTS
_POSIX_VERSION
_SC_VERSION
_POSIX_V6_ILP32_OFF32
_SC_V6_ILP32_OFF32
_POSIX_V6_ILP32_OFFBIG
_SC_V6_ILP32_OFFBIG
_POSIX_V6_LP64_OFF64
_SC_V6_LP64_OFF64
_POSIX_V6_LPBIG_OFFBIG
_SC_V6_LPBIG_OFFBIG
_POSIX2_C_BIND
_SC_2_C_BIND
_POSIX2_C_DEV
_SC_2_C_DEV
_POSIX2_CHAR_TERM
_SC_2_CHAR_TERM
_POSIX2_FORT_DEV
_SC_2_FORT_DEV
_POSIX2_FORT_RUN
_SC_2_FORT_RUN
_POSIX2_LOCALEDEF
_SC_2_LOCALEDEF
_POSIX2_PBS
_SC_2_PBS
_POSIX2_PBS_ACCOUNTING
_SC_2_PBS_ACCOUNTING
_POSIX2_PBS_CHECKPOINT
_SC_2_PBS_CHECKPOINT
_POSIX2_PBS_LOCATE
_SC_2_PBS_LOCATE
_POSIX2_PBS_MESSAGE
_SC_2_PBS_MESSAGE
_POSIX2_PBS_TRACK
_SC_2_PBS_TRACK
_POSIX2_SW_DEV
_SC_2_SW_DEV
_POSIX2_UPE
_SC_2_UPE
_POSIX2_VERSION
_SC_2_VERSION
{PAGE_SIZE}
_SC_PAGE_SIZE
{PAGESIZE}
_SC_PAGESIZE
{PTHREAD_DESTRUCTOR_ITERATIONS}
_SC_THREAD_DESTRUCTOR_ITERATIONS
{PTHREAD_KEYS_MAX}
_SC_THREAD_KEYS_MAX
{PTHREAD_STACK_MIN}
_SC_THREAD_STACK_MIN
{PTHREAD_THREADS_MAX}
_SC_THREAD_THREADS_MAX
{RE_DUP_MAX}
_SC_RE_DUP_MAX
{RTSIG_MAX}
_SC_RTSIG_MAX
{SEM_NSEMS_MAX}
_SC_SEM_NSEMS_MAX
{SEM_VALUE_MAX}
_SC_SEM_VALUE_MAX
{SIGQUEUE_MAX}
_SC_SIGQUEUE_MAX
{STREAM_MAX}
_SC_STREAM_MAX
{SYMLOOP_MAX}
_SC_SYMLOOP_MAX
{TIMER_MAX}
_SC_TIMER_MAX
{TTY_NAME_MAX}
_SC_TTY_NAME_MAX
{TZNAME_MAX}
_SC_TZNAME_MAX
_XBS5_ILP32_OFF32 (LEGACY)
_SC_XBS5_ILP32_OFF32 (LEGACY)
_XBS5_ILP32_OFFBIG (LEGACY)
_SC_XBS5_ILP32_OFFBIG (LEGACY)
_XBS5_LP64_OFF64 (LEGACY)
_SC_XBS5_LP64_OFF64 (LEGACY)
_XBS5_LPBIG_OFFBIG (LEGACY)
_SC_XBS5_LPBIG_OFFBIG (LEGACY)
_XOPEN_CRYPT
_SC_XOPEN_CRYPT
_XOPEN_ENH_I18N
_SC_XOPEN_ENH_I18N
_XOPEN_LEGACY
_SC_XOPEN_LEGACY
_XOPEN_REALTIME
_SC_XOPEN_REALTIME
_XOPEN_REALTIME_THREADS
_SC_XOPEN_REALTIME_THREADS
_XOPEN_SHM
_SC_XOPEN_SHM
_XOPEN_STREAMS
_SC_XOPEN_STREAMS
_XOPEN_UNIX
_SC_XOPEN_UNIX
_XOPEN_VERSION
_SC_XOPEN_VERSION
RETURN VALUE
If name is an invalid value, sysconf() shall return -1 and set errno to indicate the error. If the variable corresponding to name has no limit, sysconf() shall return -1 without changing the value of errno. Note that indefinite limits do not imply infinite limits; see
Otherwise, sysconf() shall return the current variable value on the system. The value returned shall not be more restrictive than the corresponding value described to the application when it was compiled with the implementation's
If the variable corresponding to name is dependent on an unsupported option, the results are unspecified.
ERRORS
The sysconf() function shall fail if:
[EINVAL]
The value of the name argument is invalid.
--------------------------------------------------------------------------------
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
As -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno to 0, then call sysconf(), and, if it returns -1, check to see if errno is non-zero.
Application writers should check whether an option, such as _POSIX_TRACE, is supported prior to obtaining and using values for related variables, such as _POSIX_TRACE_NAME_MAX.
RATIONALE
This functionality was added in response to requirements of application developers and of system vendors who deal with many international system configurations. It is closely related to pathconf() and fpathconf().
Although a conforming application can run on all systems by never demanding more resources than the minimum values published in this volume of IEEE Std 1003.1-2001, it is useful for that application to be able to use the actual value for the quantity of a resource available on any given system. To do this, the application makes use of the value of a symbolic constant in
However, once compiled, the application must still be able to cope if the amount of resource available is increased. To that end, an application may need a means of determining the quantity of a resource, or the presence of an option, at execution time.
Two examples are offered:
Applications may wish to act differently on systems with or without job control. Applications vendors who wish to distribute only a single binary package to all instances of a computer architecture would be forced to assume job control is never available if it were to rely solely on the
International applications vendors occasionally require knowledge of the number of clock ticks per second. Without these facilities, they would be required to either distribute their applications partially in source form or to have 50 Hz and 60 Hz versions for the various countries in which they operate.
It is the knowledge that many applications are actually distributed widely in executable form that leads to this facility. If limited to the most restrictive values in the headers, such applications would have to be prepared to accept the most limited environments offered by the smallest microcomputers. Although this is entirely portable, there was a consensus that they should be able to take advantage of the facilities offered by large systems, without the restrictions associated with source and object distributions.
During the discussions of this feature, it was pointed out that it is almost always possible for an application to discern what a value might be at runtime by suitably testing the various functions themselves. And, in any event, it could always be written to adequately deal with error returns from the various functions. In the end, it was felt that this imposed an unreasonable level of complication and sophistication on the application writer.
This runtime facility is not meant to provide ever-changing values that applications have to check multiple times. The values are seen as changing no more frequently than once per system initialization, such as by a system administrator or operator with an automatic configuration program. This volume of IEEE Std 1003.1-2001 specifies that they shall not change within the lifetime of the process.
Some values apply to the system overall and others vary at the file system or directory level. The latter are described in pathconf().
Note that all values returned must be expressible as integers. String values were considered, but the additional flexibility of this approach was rejected due to its added complexity of implementation and use.
Some values, such as {PATH_MAX}, are sometimes so large that they must not be used to, say, allocate arrays. The sysconf() function returns a negative value to show that this symbolic constant is not even defined in this case.
Similar to pathconf(), this permits the implementation not to have a limit. When one resource is infinite, returning an error indicating that some other resource limit has been reached is conforming behavior.
FUTURE DIRECTIONS
None.
SEE ALSO
confstr(), pathconf(), the Base Definitions volume of IEEE Std 1003.1-2001,
CHANGE HISTORY
First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.
Issue 5
The DESCRIPTION is updated for alignment with the POSIX Realtime Extension and the POSIX Threads Extension.
The _XBS_ variables and name values are added to the table of system variables in the DESCRIPTION. These are all marked EX.
Issue 6
The symbol CLK_TCK is obsolescent and removed. It is replaced with the phrase "clock ticks per second".
The symbol {PASS_MAX} is removed.
The following changes were made to align with the IEEE P1003.1a draft standard:
Table entries are added for the following variables: _SC_REGEXP, _SC_SHELL, _SC_REGEX_VERSION, _SC_SYMLOOP_MAX.
The following sysconf() variables and their associated names are added for alignment with IEEE Std 1003.1d-1999:
_POSIX_ADVISORY_INFO
_POSIX_CPUTIME
_POSIX_SPAWN
_POSIX_SPORADIC_SERVER
_POSIX_THREAD_CPUTIME
_POSIX_THREAD_SPORADIC_SERVER
_POSIX_TIMEOUTS
The following changes are made to the DESCRIPTION for alignment with IEEE Std 1003.1j-2000:
A statement expressing the dependency of support for some system variables on implementation options is added.
The following system variables are added:
_POSIX_BARRIERS
_POSIX_CLOCK_SELECTION
_POSIX_MONOTONIC_CLOCK
_POSIX_READER_WRITER_LOCKS
_POSIX_SPIN_LOCKS
_POSIX_TYPED_MEMORY_OBJECTS
The following system variables are added for alignment with IEEE Std 1003.2d-1994:
_POSIX2_PBS
_POSIX2_PBS_ACCOUNTING
_POSIX2_PBS_LOCATE
_POSIX2_PBS_MESSAGE
_POSIX2_PBS_TRACK
The following sysconf() variables and their associated names are added for alignment with IEEE Std 1003.1q-2000:
_POSIX_TRACE
_POSIX_TRACE_EVENT_FILTER
_POSIX_TRACE_INHERIT
_POSIX_TRACE_LOG
The macros associated with the c89 programming models are marked LEGACY, and new equivalent macros associated with c99 are introduced.
IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/62 is applied, updating the DESCRIPTION to denote that the _PC* and _SC* symbols are now required to be supported. A corresponding change has been made in the Base Definitions volume of IEEE Std 1003.1-2001. The deletion in the second paragraph removes some duplicated text. Additional symbols that were erroneously omitted from this reference page have been added.
IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/63 is applied, making it clear in the RETURN VALUE section that the value returned for sysconf(_SC_OPEN_MAX) may change if a call to setrlimit() adjusts the RLIMIT_NOFILE soft limit.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/134 is applied, updating the DESCRIPTION to remove an erroneous entry for _POSIX_SYMLOOP_MAX. This corrects an error in IEEE Std 1003.1-2001/Cor 1-2002.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/135 is applied, removing _POSIX_FILE_LOCKING, _POSIX_MULTI_PROCESS, _POSIX2_C_VERSION, and _XOPEN_XCU_VERSION (and their associated _SC_* variables) from the DESCRIPTION and APPLICATION USAGE sections.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/136 is applied, adding _POSIX_SS_REPL_MAX, _POSIX_TRACE_EVENT_NAME_MAX, _POSIX_TRACE_NAME_MAX, _POSIX_TRACE_SYS_MAX, and _POSIX_TRACE_USER_EVENT_MAX (and their associated _SC_* variables) to the DESCRIPTION. The RETURN VALUE and APPLICATION USAGE sections are updated to note that if variables are dependent on unsupported options, the results are unspecified.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/137 is applied, removing _REGEX_VERSION and _SC_REGEX_VERSION.
End of informative text.
--------------------------------------------------------------------------------
UNIX ® is a registered Trademark of The Open Group.
POSIX ® is a registered Trademark of The IEEE.
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--------------------------------------------------------------------------------