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NAME


unistd.h, unistd - standard symbolic constants and types

SYNOPSIS


#include <unistd.h>


DESCRIPTION


The <unistd.h> header defines the symbolic constants and structures which
are not already defined or declared in some other header. The contents of
this header are shown below.

Version Test Macros


The following symbolic constants are defined (with fixed values):

_POSIX_VERSION
Integer value indicating version of the POSIX
standard (C language binding). See standards(5).


_POSIX2_VERSION
Integer value indicating version of the POSIX.2
standard (Commands).


_POSIX2_C_VERSION
Integer value indicating version of the POSIX.2
standard (C language binding).


_XOPEN_VERSION
Integer value indicating version of the XPG to
which system conforms.


_XOPEN_XCU_VERSION
Integer value indicating the version of the XCU
specification to which the implementation conforms.
If this constant is not defined, use the
sysconf(3C) function to determine which features
are supported. This constant is not defined for the
SUSv3 environment.


Mandatory Symbolic Constants


The following symbolic constants, if defined in <unistd.h>, have a value
of -1, 0, or greater, unless otherwise specified below. If these are
undefined, the fpathconf(2), pathconf(2), or sysconf(3C) functions can be
used to determine whether the option is provided for a particular
invocation of the application.


If a symbolic constant is defined with the value -1, the option is not
supported. Headers, data types, and function interfaces required only for
the option need not be supplied. An application that attempts to use
anything associated only with the option is considered to be requiring an
extension.


If a symbolic constant is defined with a value greater than zero, the
option is always supported when the application is executed. All headers,
data types, and functions are present and operate as specified.


If a symbolic constant is defined with the value zero, all headers, data
types, and functions are present. The application can check at runtime to
see whether the option is supported by calling fpathconf(), pathconf(),
or sysconf() with the indicated name parameter.


Unless explicitly specified otherwise, the behavior of functions
associated with an unsupported option is unspecified, and an application
that uses such functions without first checking fpathconf(), pathconf(),
or sysconf() is considered to be requiring an extension.

_POSIX_ADVISORY_INFO

Implementation supports the Advisory Information option.


_POSIX_ASYNCHRONOUS_IO

Implementation supports the Asynchronous Input and Output option.


_POSIX_BARRIERS

Implementation supports the Barriers option.


_POSIX_CLOCK_SELECTION

Implementation supports the Clock Selection option.


_POSIX_CPUTIME

Implementation supports the Process CPU-Time Clocks option.


_POSIX_FSYNC

Implementation supports the File Synchronisation option.


_POSIX_IPV6

Implementation supports the IPv6 option.


_POSIX_JOB_CONTROL

Implementation supports job control.


_POSIX_MAPPED_FILES

Implementation supports the Memory Mapped Files option.


_POSIX_MEMLOCK

Implementation supports the Process Memory Locking option.


_POSIX_MEMLOCK_RANGE

Implementation supports the Range Memory Locking option.


_POSIX_MEMORY_PROTECTION

Implementation supports the Memory Protection option.


_POSIX_MESSAGE_PASSING

Implementation supports the Message Passing option.


_POSIX_MONOTONIC_CLOCK

Implementation supports the Monotonic Clock option.


_POSIX_PRIORITY_SCHEDULING

Implementation supports the Process Scheduling option.


_POSIX_RAW_SOCKETS

Implementation supports the Raw Sockets option.


_POSIX_READER_WRITER_LOCKS

Implementation supports the Read-Write Locks option.


_POSIX_REALTIME_SIGNALS

Implementation supports the Realtime Signals Extension option.


_POSIX_REGEXP

Implementation supports the Regular Expression Handling option.


_POSIX_SAVED_IDS

The exec functions (see exec(2)) save the effective user and group.


_POSIX_SEMAPHORES

Implementation supports the Semaphores option.


_POSIX_SHARED_MEMORY_OBJECTS

Implementation supports the Shared Memory Objects option.


_POSIX_SHELL

Implementation supports the POSIX shell.


_POSIX_SPAWN

Implementation supports the Spawn option.


_POSIX_SPIN_LOCKS

Implementation supports the Spin Locks option.


_POSIX_SPORADIC_SERVER

Implementation supports the Process Sporadic Server option.


_POSIX_SYNCHRONIZED_IO

Implementation supports the Synchronized Input and Output option.


_POSIX_THREAD_ATTR_STACKADDR

Implementation supports the thread stack address attribute option.


_POSIX_THREAD_ATTR_STACKSIZE

Implementation supports the thread stack size attribute option.


_POSIX_THREAD_CPUTIME

Implementation supports the Thread CPU-Time Clocks option.


_POSIX_THREAD_PROCESS_SHARED

Implementation supports the process-shared synchronization option.


_POSIX_THREAD_SAFE_FUNCTIONS

Implementation supports the thread-safe functions option.


_POSIX_THREAD_SPORADIC_SERVER

Implementation supports the Thread Sporadic Server option.


_POSIX_THREADS

Implementation supports the threads option.


_POSIX_TIMERS

Implementation supports the Timers option.


_POSIX_TIMEOUTS

Implementation supports the Timeouts option.


_POSIX_TRACE

Implementation supports the Trace option.


_POSIX_TRACE_EVENT_FILTER

Implementation supports the Trace Event Filter option.


_POSIX_TRACE_INHERIT

Implementation supports the Trace Inherit option.


_POSIX_TRACE_LOG

Implementation supports the Trace Log option.


_POSIX_TYPED_MEMORY_OBJECTS

Implementation supports the Typed Memory Objects option.


_POSIX_V6_ILP32_OFF32

Implementation provides a C-language compilation environment with
32-bit int, long, and pointer types and an off_t type using at least
64 bits.


_POSIX_V6_ILP32_OFFBIG

Implementation provides a C-language compilation environment with
32-bit int, long, and pointer types and an off_t type using at least
64 bits.


_POSIX_V6_LP64_OFF64

Implementation provides a C-language compilation environment with
32-bit int and 64-bit long, pointer, and off_t types.


_POSIX_V6_LPBIG_OFFBIG

Implementation provides a C-language compilation environment with an
int type using at least 32 bits and long, pointer, and off_t types
using at least 64 bits.


_POSIX_XOPEN_STREAMS

Implementation supports the XSI STREAMS Option Group.


_POSIX2_C_BIND

Implementation supports the C Language Binding option.


_POSIX2_C_DEV

Implementation supports the C Language Development Utilities option.


_POSIX2_CHAR_TERM

Implementation supports at least one terminal type.


_POSIX2_LOCALEDEF

Implementation supports the creation of locales by the localedef(1)
utility.


_POSIX2_PBS

Implementation supports the Batch Environment Services and Utilities
option.


_POSIX2_PBS_ACCOUNTING

Implementation supports the Batch Accounting option.


_POSIX2_PBS_CHECKPOINT

Implementation supports the Batch Checkpoint/Restart option.


_POSIX2_PBS_LOCATE

Implementation supports the Locate Batch Job Request option.


_POSIX2_PBS_MESSAGE

Implementation supports the Batch Job Message Request option.


_POSIX2_PBS_TRACK

Implementation supports the Track Batch Job Request option.


_POSIX2_SW_DEV

Implementation supports the Software Development Utilities option.


_POSIX2_UPE

Implementation supports the User Portability Utilities option.


_XBS5_ILP32_OFF32

Implementation provides a C-language compilation environment with
32-bit int, long, pointer and off_t types.


_XBS5_ILP32_OFFBIG

Implementation provides a C-language compilation environment with
32-bit int, long and pointer types and an off_t type using at least
64 bits.


_XBS5_LP64_OFF64

Implementation provides a C-language compilation environment with
32-bit int and 64-bit long, pointer and off_t types.


_XBS5_LPBIG_OFFBIG

Implementation provides a C-language compilation environment with an
int type using at least 32 bits and long, pointer and off_t types
using at least 64 bits.


_XOPEN_ENH_I18N

Implementation supports the Issue 4, Version 2 Enhanced
Internationalization Feature Group.


_XOPEN_LEGACY

Implementation supports the Legacy Feature Group.


_XOPEN_REALTIME

Implementation supports the X/Open Realtime Feature Group.


_XOPEN_SHM

Implementation supports the Issue 4, Version 2 Shared Memory Feature
Group.


_XOPEN_UNIX

X/Open CAE Specification, January 1997, System Interfaces and
Headers, Issue 5 (ISBN: 1-85912-181-0, C606).


_XOPEN_XPG3

X/Open Specification, February 1992, System Interfaces and Headers,
Issue 3 (ISBN: 1-872630-37-5, C212); this specification was formerly
X/Open Portability Guide, Issue 3, Volume 2, January 1989, XSI System
Interface and Headers (ISBN: 0-13-685843-0, XO/XPG/89/003).


_XOPEN_XPG4

X/Open CAE Specification, July 1992, System Interfaces and Headers,
Issue 4 (ISBN: 1-872630-47-2, C202).


Execution-time Symbolic Constants
If any of the following constants are not defined in the header
<unistd.h>, the value varies depending on the file to which it is
applied.


If any of the following constants are defined to have value -1 in the
header <unistd.h>, the implementation will not provide the option on any
file; if any are defined to have a value other than -1 in the header
<unistd.h>, the implementation will provide the option on all applicable
files.


All of the following constants, whether defined in <unistd.h> or not, can
be queried with respect to a specific file using the pathconf() or
fpathconf() functions.

_POSIX_ASYNC_IO
Asynchronous input or output operations can be
performed for the associated file.


_POSIX_PRIO_IO
Prioritized input or output operations can be
performed for the associated file.


_POSIX_SYNC_IO
Synchronized input or output operations can be
performed for the associated file.


Constants for Functions


The following constant is defined:

NULL
Null pointer.


The following symbolic constants are defined for the access(2) function:

R_OK
Test for read permission.


W_OK
Test for write permission.


X_OK
Test for execute (search) permission.


F_OK
Test for existence of file.


The constants F_OK, R_OK, W_OK, and X_OK, and the expressions R_OK|W_OK,
R_OK|X_OK, and R_OK|W_OK|X_OK all have distinct values.


The following symbolic constants are defined for the lockf(3C) function:

F_ULOCK
Unlock a previously locked region.


F_LOCK
Lock a region for exclusive use.


F_TLOCK
Test and lock a region for exclusive use.


F_TEST
Test a region for other processes locks.


The following symbolic constants are defined for the lseek(2) and
fcntl(2) functions (they have distinct values):

SEEK_SET
Set file offset to offset.


SEEK_CUR
Set file offset to current plus offset.


SEEK_END
Set file offset to EOF plus offset.


The following symbolic constants are defined for the confstr(3C) function
for both SPARC and x86:


_CS_LFS64_CFLAGS _CS_LFS64_LDFLAGS
_CS_LFS64_LIBS _CS_LFS64_LINTFLAGS
_CS_LFS_CFLAGS _CS_LFS_LDFLAGS
_CS_LFS_LIBS _CS_LFS_LINTFLAGS
_CS_PATH _CS_POSIX_V6_ILP32_OFF32_CFLAGS
_CS_POSIX_V6_ILP32_OFF32_LDFLAGS _CS_POSIX_V6_ILP32_OFF32_LIBS
_CS_POSIX_V6_ILP32_OFF32_LINTFLAGS _CS_POSIX_V6_ILP32_OFFBIG_CFLAGS
_CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS _CS_POSIX_V6_ILP32_OFFBIG_LIBS
_CS_POSIX_V6_ILP32_OFFBIG_LINTFLAGS _CS_POSIX_V6_WIDTH_RESTRICTED_ENV
_CS_XBS5_ILP32_OFF32_CFLAGS _CS_XBS5_ILP32_OFF32_LDFLAGS
_CS_XBS5_ILP32_OFF32_LIBS _CS_XBS5_ILP32_OFF32_LINTFLAGS
_CS_XBS5_ILP32_OFFBIG_CFLAGS _CS_XBS5_ILP32_OFFBIG_LDFLAGS
_CS_XBS5_ILP32_OFFBIG_LIBS _CS_XBS5_ILP32_OFFBIG_LINTFLAGS


The followwing symbolic constants are defined for the confstr() function
for SPARC only:


_CS_POSIX_V6_LP64_OFF64_CFLAGS _CS_POSIX_V6_LP64_OFF64_LDFLAGS
_CS_POSIX_V6_LP64_OFF64_LIBS _CS_POSIX_V6_LP64_OFF64_LINTFLAGS
_CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS _CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS
_CS_POSIX_V6_LPBIG_OFFBIG_LIBS _CS_POSIX_V6_LPBIG_OFFBIG_LINTFLAGS
_CS_XBS5_LP64_OFF64_CFLAGS _CS_XBS5_LP64_OFF64_LDFLAGS
_CS_XBS5_LP64_OFF64_LIBS _CS_XBS5_LP64_OFF64_LINTFLAGS
_CS_XBS5_LPBIG_OFFBIG_CFLAGS _CS_XBS5_LPBIG_OFFBIG_LDFLAGS
_CS_XBS5_LPBIG_OFFBIG_LIBS _CS_XBS5_LPBIG_OFFBIG_LINTFLAGS


The following symbolic constants are defined for the sysconf(3C)
function:


_SC_2_C_BIND _SC_2_C_DEV
_SC_2_C_VERSION _SC_2_FORT_DEV
_SC_2_FORT_RUN _SC_2_LOCALEDEF
_SC_2_PBS _SC_2_PBS_ACCOUNTING
_SC_2_PBS_CHECKPOINT _SC_2_PBS_LOCATE
_SC_2_PBS_MESSAGE _SC_2_PBS_TRACK
_SC_2_SW_DEV _SC_2_UPE
_SC_2_VERSION _SC_ADVISORY_INFO
_SC_AIO_LISTIO_MAX _SC_AIO_MAX
_SC_AIO_PRIO_DELTA_MAX _SC_ARG_MAX
_SC_ASYNCHRONOUS_IO _SC_ATEXIT_MAX
_SC_AVPHYS_PAGES _SC_BARRIERS
_SC_BC_BASE_MAX _SC_BC_DIM_MAX
_SC_BC_SCALE_MAX _SC_BC_STRING_MAX
_SC_CHILD_MAX _SC_CLK_TCK
_SC_CLOCK_SELECTION _SC_COLL_WEIGHTS_MAX
_SC_CPUTIME _SC_DELAYTIMER_MAX
_SC_EXPR_NEST_MAX _SC_FSYNC
_SC_GETGR_R_SIZE_MAX _SC_GETPW_R_SIZE_MAX
_SC_HOST_NAME_MAX _SC_IOV_MAX
_SC_IPV6 _SC_JOB_CONTROL
_SC_LINE_MAX _SC_LOGIN_NAME_MAX
_SC_LOGNAME_MAX _SC_MAPPED_FILES
_SC_MEMLOCK _SC_MEMLOCK_RANGE
_SC_MEMORY_PROTECTION _SC_MESSAGE_PASSING
_SC_MONOTONIC_CLOCK _SC_MQ_OPEN_MAX
_SC_MQ_PRIO_MAX _SC_NGROUPS_MAX
_SC_NPROCESSORS_CONF _SC_NPROCESSORS_ONLN
_SC_OPEN_MAX _SC_PAGESIZE
_SC_PAGE_SIZE _SC_PASS_MAX
_SC_PHYS_PAGES _SC_PRIORITIZED_IO
_SC_PRIORITY_SCHEDULING _SC_RAW_SOCKETS
_SC_READER_WRITER_LOCKS _SC_REALTIME_SIGNALS
_SC_REGEXP _SC_RE_DUP_MAX
_SC_RTSIG_MAX _SC_SAVED_IDS
_SC_SEMAPHORES _SC_SEM_NSEMS_MAX
_SC_SEM_VALUE_MAX _SC_SHARED_MEMORY_OBJECTS
_SC_SHELL _SC_SIGQUEUE_MAX
_SC_SPAWN _SC_SPIN_LOCKS
_SC_SPORADIC_SERVER _SC_SS_REPL_MAX
_SC_STREAM_MAX _SC_SYMLOOP_MAX
_SC_SYNCHRONIZED_IO _SC_THREAD_ATTR_STACKADDR
_SC_THREAD_ATTR_STACKSIZE _SC_THREAD_CPUTIME
_SC_THREAD_DESTRUCTOR_ITERATIONS _SC_THREAD_KEYS_MAX
_SC_THREAD_PRIO_INHERIT _SC_THREAD_PRIO_PROTECT
_SC_THREAD_PRIORITY_SCHEDULING _SC_THREAD_PROCESS_SHARED
_SC_THREAD_SPORADIC_SERVER _SC_THREADS
_SC_THREAD_SAFE_FUNCTIONS _SC_THREAD_STACK_MIN
_SC_THREAD_THREADS_MAX _SC_TIMEOUTS
_SC_TIMER_MAX _SC_TIMERS
_SC_TRACE _SC_TRACE_EVENT_FILTER
_SC_TRACE_EVENT_NAME_MAX _SC_TRACE_INHERIT
_SC_TRACE_LOG _SC_TRACE_NAME_MAX
_SC_TRACE_SYS_MAX _SC_TRACE_USER_EVENT_MAX
_SC_TTY_NAME_MAX _SC_TYPED_MEMORY_OBJECTS
_SC_TZNAME_MAX _SC_V6_ILP32_OFF32
_SC_V6_ILP32_OFFBIG _SC_V6_LP64_OFF64
_SC_V6_LPBIG_OFFBIG _SC_VERSION
_SC_XBS5_ILP32_OFF32 _SC_XBS5_ILP32_OFFBIG
_SC_XBS5_LP64_OFF64 _SC_XBS5_LPBIG_OFFBIG
_SC_XOPEN_CRYPT _SC_XOPEN_ENH_I18N
_SC_XOPEN_SHM _SC_XOPEN_STREAMS
_SC_XOPEN_UNIX _SC_XOPEN_VERSION
_SC_XOPEN_XCU_VERSION


The constants _SC_PAGESIZE and _SC_PAGE_SIZE can be defined to have the
same value.


The following symbolic constants are defined for the fpathconf(2)
function:


_PC_2_SYMLINKS _PC_ALLOC_SIZE_MIN
_PC_ASYNC_IO _PC_CHOWN_RESTRICTED
_PC_FILESIZEBITS _PC_LINK_MAX
_PC_MAX_CANON _PC_MAX_INPUT
_PC_NAME_MAX _PC_NO_TRUNC
_PC_PATH_MAX _PC_PIPE_BUF
_PC_PRIO_IO _PC_REC_INCR_XFER_SIZE
_PC_REC_MAX_XFER_SIZE _PC_REC_MIN_XFER_SIZE
_PC_REC_XFER_ALIGN _PC_SYMLINK_MAX
_PC_SYNC_IO _PC_TIMESTAMP_RESOLUTION
_PC_VDISABLE _PC_XATTR_ENABLED
_PC_XATTR_EXISTS


The following symbolic constants are defined for file streams:

STDIN_FILENO
File number (0) of stdin.


STDOUT_FILENO
File number (1) of stout.


STDERR_FILENO
File number (2) of stderr.


The following pathnames are defined:

GF_PATH
Pathname of the group file.


PF_PATH
Pathname of the passwd file.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|Standard | See standards(5). |
+--------------------+-------------------+

SEE ALSO


access(2), exec(2), fcntl(2), fpathconf(2), lseek(2), confstr(3C),
lockf(3C), sysconf(3C), termios(3C), group(4), passwd(4), attributes(5),
standards(5), termio(7I)


September 1, 2009 UNISTD.H(3HEAD)