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Copyright 1989 AT&T
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#include <unistd.h>
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.
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.
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
_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).
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.
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.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Interface Stability | Committed |
| Standard | See standards(5). |
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)