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Standard for Information Technology -- Portable Operating System
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Copyright 1989 AT&T
Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved.
#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).
Integer value indicating version of the POSIX.2 standard (Commands).
Integer value indicating version of the POSIX.2 standard (C language binding).
Integer value indicating version of the XPG to which system conforms.
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.
Implementation supports the Asynchronous Input and Output option.
Implementation supports the Barriers option.
Implementation supports the Clock Selection option.
Implementation supports the Process CPU-Time Clocks option.
Implementation supports the File Synchronisation option.
Implementation supports the IPv6 option.
Implementation supports job control.
Implementation supports the Memory Mapped Files option.
Implementation supports the Process Memory Locking option.
Implementation supports the Range Memory Locking option.
Implementation supports the Memory Protection option.
Implementation supports the Message Passing option.
Implementation supports the Monotonic Clock option.
Implementation supports the Process Scheduling option.
Implementation supports the Raw Sockets option.
Implementation supports the Read-Write Locks option.
Implementation supports the Realtime Signals Extension option.
Implementation supports the Regular Expression Handling option.
The exec functions (see exec(2)) save the effective user and group.
Implementation supports the Semaphores option.
Implementation supports the Shared Memory Objects option.
Implementation supports the POSIX shell.
Implementation supports the Spawn option.
Implementation supports the Spin Locks option.
Implementation supports the Process Sporadic Server option.
Implementation supports the Synchronized Input and Output option.
Implementation supports the thread stack address attribute option.
Implementation supports the thread stack size attribute option.
Implementation supports the Thread CPU-Time Clocks option.
Implementation supports the process-shared synchronization option.
Implementation supports the thread-safe functions option.
Implementation supports the Thread Sporadic Server option.
Implementation supports the threads option.
Implementation supports the Timers option.
Implementation supports the Timeouts option.
Implementation supports the Trace option.
Implementation supports the Trace Event Filter option.
Implementation supports the Trace Inherit option.
Implementation supports the Trace Log option.
Implementation supports the Typed Memory Objects option.
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.
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.
Implementation provides a C-language compilation environment with 32-bit int and 64-bit long, pointer, and off_t types.
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.
Implementation supports the XSI STREAMS Option Group.
Implementation supports the C Language Binding option.
Implementation supports the C Language Development Utilities option.
Implementation supports at least one terminal type.
Implementation supports the creation of locales by the localedef(1) utility.
Implementation supports the Batch Environment Services and Utilities option.
Implementation supports the Batch Accounting option.
Implementation supports the Batch Checkpoint/Restart option.
Implementation supports the Locate Batch Job Request option.
Implementation supports the Batch Job Message Request option.
Implementation supports the Track Batch Job Request option.
Implementation supports the Software Development Utilities option.
Implementation supports the User Portability Utilities option.
Implementation provides a C-language compilation environment with 32-bit int, long, pointer and off_t types.
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.
Implementation provides a C-language compilation environment with 32-bit int and 64-bit long, pointer and off_t types.
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.
Implementation supports the Issue 4, Version 2 Enhanced Internationalization Feature Group.
Implementation supports the Legacy Feature Group.
Implementation supports the Issue 4, Version 2 Shared Memory Feature Group.
X/Open CAE Specification, January 1997, System Interfaces and Headers, Issue 5 (ISBN: 1-85912-181-0, C606).
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).
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.
Prioritized input or output operations can be performed for the associated file.
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.
Test for write permission.
Test for execute (search) permission.
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.
Lock a region for exclusive use.
Test and lock a region for exclusive use.
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.
Set file offset to current plus offset.
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.
File number (1) of stout.
File number (2) of stderr.
The following pathnames are defined: GF_PATH
Pathname of the group file.
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)