'\" et .TH unistd.h "0P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual" .SH PROLOG This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. .SH NAME unistd.h \(em standard symbolic constants and types .SH SYNOPSIS .LP .nf #include .fi .SH DESCRIPTION The .IR header defines miscellaneous symbolic constants and types, and declares miscellaneous functions. The actual values of the constants are unspecified except as shown. The contents of this header are shown below. .SS "Version Test Macros" .P The .IR header shall define the following symbolic constants. The values shall be suitable for use in .BR #if preprocessing directives. .IP _POSIX_VERSION 6 .br Integer value indicating version of this standard (C-language binding) to which the implementation conforms. For implementations conforming to POSIX.1\(hy2008, the value shall be 200809L. .IP _POSIX2_VERSION 6 .br Integer value indicating version of the Shell and Utilities volume of POSIX.1 to which the implementation conforms. For implementations conforming to POSIX.1\(hy2008, the value shall be 200809L. For profile implementations that define _POSIX_SUBPROFILE (see .IR "Section 2.1.5.1" ", " "Subprofiling Considerations") in .IR , POSIX2_VERSION may be left undefined or be defined with the value \(mi1 to indicate that the Shell and Utilities volume of POSIX.1 is not supported. In this case, a call to .IR sysconf(_SC_2_VERSION) shall return either 200809L or \(mi1 indicating that the Shell and Utilities volume of POSIX.1 is or is not, respectively, supported at runtime. .P The .IR header shall define the following symbolic constant only if the implementation supports the XSI option; see .IR "Section 2.1.4" ", " "XSI Conformance". If defined, its value shall be suitable for use in .BR #if preprocessing directives. .IP _XOPEN_VERSION 6 .br Integer value indicating version of the X/Open Portability Guide to which the implementation conforms. The value shall be 700. .SS "Constants for Options and Option Groups" .P The following symbolic constants, if defined in .IR , shall have a value of \(mi1, 0, or greater, unless otherwise specified below. For profile implementations that define _POSIX_SUBPROFILE (see .IR "Section 2.1.5.1" ", " "Subprofiling Considerations") in .IR , constants described below as always having a value greater than zero need not be defined and, if defined, may have a value of \(mi1, 0, or greater. The values shall be suitable for use in .BR #if preprocessing directives. .P If a symbolic constant is not defined or is defined with the value \(mi1, the option is not supported for compilation. If it is defined with a value greater than zero, the option shall always be supported when the application is executed. If it is defined with the value zero, the option shall be supported for compilation and might or might not be supported at runtime. See .IR "Section 2.1.6" ", " "Options" for further information about the conformance requirements of these three categories of support. .IP _POSIX_ADVISORY_INFO 6 .br The implementation supports the Advisory Information option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_ASYNCHRONOUS_IO 6 .br The implementation supports asynchronous input and output. This symbol shall always be set to the value 200809L. .IP _POSIX_BARRIERS 6 .br The implementation supports barriers. This symbol shall always be set to the value 200809L. .IP _POSIX_CHOWN_RESTRICTED 6 .br The use of \fIchown\fR() and \fIfchown\fR() is restricted to a process with appropriate privileges, and to changing the group ID of a file only to the effective group ID of the process or to one of its supplementary group IDs. This symbol shall be defined with a value other than \(mi1. .IP _POSIX_CLOCK_SELECTION 6 .br The implementation supports clock selection. This symbol shall always be set to the value 200809L. .IP _POSIX_CPUTIME 6 .br The implementation supports the Process CPU-Time Clocks option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_FSYNC 6 .br The implementation supports the File Synchronization option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_IPV6 6 .br The implementation supports the IPv6 option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_JOB_CONTROL 6 .br The implementation supports job control. This symbol shall always be set to a value greater than zero. .IP _POSIX_MAPPED_FILES 6 .br The implementation supports memory mapped Files. This symbol shall always be set to the value 200809L. .IP _POSIX_MEMLOCK 6 .br The implementation supports the Process Memory Locking option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_MEMLOCK_RANGE 6 .br The implementation supports the Range Memory Locking option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_MEMORY_PROTECTION 6 .br The implementation supports memory protection. This symbol shall always be set to the value 200809L. .IP _POSIX_MESSAGE_PASSING 6 .br The implementation supports the Message Passing option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_MONOTONIC_CLOCK 6 .br The implementation supports the Monotonic Clock option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_NO_TRUNC 6 .br Pathname components longer than {NAME_MAX} generate an error. This symbol shall be defined with a value other than \(mi1. .IP _POSIX_PRIORITIZED_IO 6 .br The implementation supports the Prioritized Input and Output option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_PRIORITY_SCHEDULING 6 .br The implementation supports the Process Scheduling option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_RAW_SOCKETS 6 .br The implementation supports the Raw Sockets option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_READER_WRITER_LOCKS 6 .br The implementation supports read-write locks. This symbol shall always be set to the value 200809L. .IP _POSIX_REALTIME_SIGNALS 6 .br The implementation supports realtime signals. This symbol shall always be set to the value 200809L. .IP _POSIX_REGEXP 6 .br The implementation supports the Regular Expression Handling option. This symbol shall always be set to a value greater than zero. .IP _POSIX_SAVED_IDS 6 .br Each process has a saved set-user-ID and a saved set-group-ID. This symbol shall always be set to a value greater than zero. .IP _POSIX_SEMAPHORES 6 .br The implementation supports semaphores. This symbol shall always be set to the value 200809L. .IP _POSIX_SHARED_MEMORY_OBJECTS 6 .br The implementation supports the Shared Memory Objects option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_SHELL 6 .br The implementation supports the POSIX shell. This symbol shall always be set to a value greater than zero. .IP _POSIX_SPAWN 6 .br The implementation supports the Spawn option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_SPIN_LOCKS 6 .br The implementation supports spin locks. This symbol shall always be set to the value 200809L. .IP _POSIX_SPORADIC_SERVER 6 .br The implementation supports the Process Sporadic Server option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_SYNCHRONIZED_IO 6 .br The implementation supports the Synchronized Input and Output option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_ATTR_STACKADDR 6 .br The implementation supports the Thread Stack Address Attribute option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_ATTR_STACKSIZE 6 .br The implementation supports the Thread Stack Size Attribute option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_CPUTIME 6 .br The implementation supports the Thread CPU-Time Clocks option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_PRIO_INHERIT 6 .br The implementation supports the Non-Robust Mutex Priority Inheritance option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_PRIO_PROTECT 6 .br The implementation supports the Non-Robust Mutex Priority Protection option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_PRIORITY_SCHEDULING 6 .br The implementation supports the Thread Execution Scheduling option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_PROCESS_SHARED 6 .br The implementation supports the Thread Process-Shared Synchronization option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_ROBUST_PRIO_INHERIT 6 .br The implementation supports the Robust Mutex Priority Inheritance option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_ROBUST_PRIO_PROTECT 6 .br The implementation supports the Robust Mutex Priority Protection option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREAD_SAFE_FUNCTIONS 6 .br The implementation supports thread-safe functions. This symbol shall always be set to the value 200809L. .IP _POSIX_THREAD_SPORADIC_SERVER 6 .br The implementation supports the Thread Sporadic Server option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_THREADS 6 .br The implementation supports threads. This symbol shall always be set to the value 200809L. .IP _POSIX_TIMEOUTS 6 .br The implementation supports timeouts. This symbol shall always be set to the value 200809L. .IP _POSIX_TIMERS 6 .br The implementation supports timers. This symbol shall always be set to the value 200809L. .IP _POSIX_TRACE 6 .br The implementation supports the Trace option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_TRACE_EVENT_FILTER 6 .br The implementation supports the Trace Event Filter option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_TRACE_INHERIT 6 .br The implementation supports the Trace Inherit option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_TRACE_LOG 6 .br The implementation supports the Trace Log option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_TYPED_MEMORY_OBJECTS 6 .br The implementation supports the Typed Memory Objects option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX_V6_ILP32_OFF32 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int , .BR long , .BR pointer , and .BR off_t types. .IP _POSIX_V6_ILP32_OFFBIG 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int , .BR long , and .BR pointer types and an .BR off_t type using at least 64 bits. .IP _POSIX_V6_LP64_OFF64 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int and 64-bit .BR long , .BR pointer , and .BR off_t types. .IP _POSIX_V6_LPBIG_OFFBIG 6 .br The implementation provides a C-language compilation environment with an .BR int type using at least 32 bits and .BR long , .BR pointer , and .BR off_t types using at least 64 bits. .IP _POSIX_V7_ILP32_OFF32 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int , .BR long , .BR pointer , and .BR off_t types. .IP _POSIX_V7_ILP32_OFFBIG 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int , .BR long , and .BR pointer types and an .BR off_t type using at least 64 bits. .IP _POSIX_V7_LP64_OFF64 6 .br The implementation provides a C-language compilation environment with 32-bit .BR int and 64-bit .BR long , .BR pointer , and .BR off_t types. .IP _POSIX_V7_LPBIG_OFFBIG 6 .br The implementation provides a C-language compilation environment with an .BR int type using at least 32 bits and .BR long , .BR pointer , and .BR off_t types using at least 64 bits. .IP _POSIX2_C_BIND 6 .br The implementation supports the C-Language Binding option. This symbol shall always have the value 200809L. .IP _POSIX2_C_DEV 6 .br The implementation supports the C-Language Development Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_CHAR_TERM 6 .br The implementation supports the Terminal Characteristics option. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or a value greater than zero. .IP _POSIX2_FORT_DEV 6 .br The implementation supports the FORTRAN Development Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_FORT_RUN 6 .br The implementation supports the FORTRAN Runtime Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_LOCALEDEF 6 .br The implementation supports the creation of locales by the .IR localedef utility. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS 6 .br The implementation supports the Batch Environment Services and Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS_ACCOUNTING 6 .br The implementation supports the Batch Accounting option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS_CHECKPOINT 6 .br The implementation supports the Batch Checkpoint/Restart option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS_LOCATE 6 .br The implementation supports the Locate Batch Job Request option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS_MESSAGE 6 .br The implementation supports the Batch Job Message Request option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_PBS_TRACK 6 .br The implementation supports the Track Batch Job Request option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_SW_DEV 6 .br The implementation supports the Software Development Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _POSIX2_UPE 6 .br The implementation supports the User Portability Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall either be \(mi1 or 200809L. .IP _XOPEN_CRYPT 6 .br The implementation supports the X/Open Encryption Option Group. .IP _XOPEN_ENH_I18N 6 .br The implementation supports the Issue 4, Version 2 Enhanced Internationalization Option Group. This symbol shall always be set to a value other than \(mi1. .IP _XOPEN_REALTIME 6 .br The implementation supports the X/Open Realtime Option Group. .IP _XOPEN_REALTIME_THREADS 6 .br The implementation supports the X/Open Realtime Threads Option Group. .IP _XOPEN_SHM 6 .br The implementation supports the Issue 4, Version 2 Shared Memory Option Group. This symbol shall always be set to a value other than \(mi1. .IP _XOPEN_STREAMS 6 .br The implementation supports the XSI STREAMS Option Group. .IP _XOPEN_UNIX 6 .br The implementation supports the XSI option. .IP _XOPEN_UUCP 6 .br The implementation supports the UUCP Utilities option. If this symbol is defined in .IR , it shall be defined to be \(mi1, 0, or 200809L. The value of this symbol reported by \fIsysconf\fR() shall be either \(mi1 or 200809L. .SS "Execution-Time Symbolic Constants" .P If any of the following symbolic constants are not defined in the .IR header, the value shall vary depending on the file to which it is applied. If defined, they shall have values suitable for use in .BR #if preprocessing directives. .P If any of the following symbolic constants are defined to have value \(mi1 in the .IR header, the implementation shall not provide the option on any file; if any are defined to have a value other than \(mi1 in the .IR header, the implementation shall provide the option on all applicable files. .P All of the following values, whether defined as symbolic constants in .IR or not, may be queried with respect to a specific file using the \fIpathconf\fR() or \fIfpathconf\fR() functions: .IP _POSIX_ASYNC_IO 6 .br Asynchronous input or output operations may be performed for the associated file. .IP _POSIX_PRIO_IO 6 .br Prioritized input or output operations may be performed for the associated file. .IP _POSIX_SYNC_IO 6 .br Synchronized input or output operations may be performed for the associated file. .P If the following symbolic constants are defined in the .IR header, they apply to files and all paths in all file systems on the implementation: .IP _POSIX_TIMESTAMP_RESOLUTION 6 .br The resolution in nanoseconds for all file timestamps. .IP _POSIX2_SYMLINKS 6 .br Symbolic links can be created. .SS "Constants for Functions" .P The .IR header shall define NULL as described in .IR . .P The .IR header shall define the following symbolic constants for use with the \fIaccess\fR() function. The values shall be suitable for use in .BR #if preprocessing directives. .IP F_OK 12 Test for existence of file. .IP R_OK 12 Test for read permission. .IP W_OK 12 Test for write permission. .IP X_OK 12 Test for execute (search) permission. .P The constants F_OK, R_OK, W_OK, and X_OK and the expressions \fIR_OK\fP|\fIW_OK\fP, \fIR_OK\fP|\fIX_OK\fP, and \fIR_OK\fP|\fIW_OK\fP|\fIX_OK\fP shall all have distinct values. .P The .IR header shall define the following symbolic constants for the \fIconfstr\fR() function: .IP _CS_PATH 6 .br This is the value for the .IR PATH environment variable that finds all standard utilities. .IP _CS_POSIX_V7_ILP32_OFF32_CFLAGS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFF32) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of initial options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_ILP32_OFF32_LDFLAGS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFF32) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of final options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_ILP32_OFF32_LIBS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFF32) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of libraries to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_ILP32_OFFBIG_CFLAGS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of initial options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , and .BR pointer types, and an .BR off_t type using at least 64 bits. .IP _CS_POSIX_V7_ILP32_OFFBIG_LDFLAGS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of final options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , and .BR pointer types, and an .BR off_t type using at least 64 bits. .IP _CS_POSIX_V7_ILP32_OFFBIG_LIBS 6 .br If \fIsysconf\fP(_SC_V7_ILP32_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of libraries to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int , .BR long , and .BR pointer types, and an .BR off_t type using at least 64 bits. .IP _CS_POSIX_V7_LP64_OFF64_CFLAGS 6 .br If \fIsysconf\fP(_SC_V7_LP64_OFF64) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of initial options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int and 64-bit .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_LP64_OFF64_LDFLAGS 6 .br If \fIsysconf\fP(_SC_V7_LP64_OFF64) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of final options to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int and 64-bit .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_LP64_OFF64_LIBS 6 .br If \fIsysconf\fP(_SC_V7_LP64_OFF64) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of libraries to be given to the .IR c99 utility to build an application using a programming model with 32-bit .BR int and 64-bit .BR long , .BR pointer , and .BR off_t types. .IP _CS_POSIX_V7_LPBIG_OFFBIG_CFLAGS 6 .br If \fIsysconf\fP(_SC_V7_LPBIG_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of initial options to be given to the .IR c99 utility to build an application using a programming model with an .BR int type using at least 32 bits and .BR long , .BR pointer , and .BR off_t types using at least 64 bits. .IP _CS_POSIX_V7_LPBIG_OFFBIG_LDFLAGS 6 .br If \fIsysconf\fP(_SC_V7_LPBIG_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of final options to be given to the .IR c99 utility to build an application using a programming model with an .BR int type using at least 32 bits and .BR long , .BR pointer , and .BR off_t types using at least 64 bits. .IP _CS_POSIX_V7_LPBIG_OFFBIG_LIBS 6 .br If \fIsysconf\fP(_SC_V7_LPBIG_OFFBIG) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of libraries to be given to the .IR c99 utility to build an application using a programming model with an .BR int type using at least 32 bits and .BR long , .BR pointer , and .BR off_t types using at least 64 bits. .IP _CS_POSIX_V7_THREADS_CFLAGS 6 .br If .IR sysconf (_SC_POSIX_THREADS) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of initial options to be given to the .IR c99 utility to build a multi-threaded application. These flags are in addition to those associated with any of the other _CS_POSIX_V7_*_CFLAGS values used to specify particular type size programing environments. .IP _CS_POSIX_V7_THREADS_LDFLAGS 6 .br If .IR sysconf (_SC_POSIX_THREADS) returns \(mi1, the meaning of this value is unspecified. Otherwise, this value is the set of final options to be given to the .IR c99 utility to build a multi-threaded application. These flags are in addition to those associated with any of the other _CS_POSIX_V7_*_LDFLAGS values used to specify particular type size programing environments. .IP _CS_POSIX_V7_WIDTH_RESTRICTED_ENVS 6 .br This value is a -separated list of names of programming environments supported by the implementation in which the widths of the .BR blksize_t , .BR cc_t , .BR mode_t , .BR nfds_t , .BR pid_t , .BR ptrdiff_t , .BR size_t , .BR speed_t , .BR ssize_t , .BR suseconds_t , .BR tcflag_t , .BR wchar_t , and .BR wint_t types are no greater than the width of type .BR long . The format of each name shall be suitable for use with the .IR getconf .BR \(miv option. .IP _CS_V7_ENV 6 .br This is the value that provides the environment variable information (other than that provided by _CS_PATH) that is required by the implementation to create a conforming environment, as described in the implementation's conformance documentation. .br .P The following symbolic constants are reserved for compatibility with Issue 6: .P .nf _CS_POSIX_V6_ILP32_OFF32_CFLAGS _CS_POSIX_V6_ILP32_OFF32_LDFLAGS _CS_POSIX_V6_ILP32_OFF32_LIBS _CS_POSIX_V6_ILP32_OFFBIG_CFLAGS _CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS _CS_POSIX_V6_ILP32_OFFBIG_LIBS _CS_POSIX_V6_LP64_OFF64_CFLAGS _CS_POSIX_V6_LP64_OFF64_LDFLAGS _CS_POSIX_V6_LP64_OFF64_LIBS _CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS _CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS _CS_POSIX_V6_LPBIG_OFFBIG_LIBS _CS_POSIX_V6_WIDTH_RESTRICTED_ENVS _CS_V6_ENV .fi .P The .IR header shall define SEEK_CUR, SEEK_END, and SEEK_SET as described in .IR . .P The .IR header shall define the following symbolic constants as possible values for the .IR function argument to the \fIlockf\fR() function: .IP F_LOCK 12 Lock a section for exclusive use. .IP F_TEST 12 Test section for locks by other processes. .IP F_TLOCK 12 Test and lock a section for exclusive use. .IP F_ULOCK 12 Unlock locked sections. .P The .IR header shall define the following symbolic constants for \fIpathconf\fR(): .P .nf _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 .fi .P The .IR header shall define the following symbolic constants for \fIsysconf\fR(): .P .nf _SC_2_C_BIND _SC_2_C_DEV _SC_2_CHAR_TERM _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_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_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_OPEN_MAX _SC_PAGE_SIZE _SC_PAGESIZE _SC_PRIORITIZED_IO _SC_PRIORITY_SCHEDULING _SC_RAW_SOCKETS _SC_RE_DUP_MAX _SC_READER_WRITER_LOCKS _SC_REALTIME_SIGNALS _SC_REGEXP _SC_RTSIG_MAX _SC_SAVED_IDS _SC_SEM_NSEMS_MAX _SC_SEM_VALUE_MAX _SC_SEMAPHORES _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_ROBUST_PRIO_INHERIT _SC_THREAD_ROBUST_PRIO_PROTECT _SC_THREAD_SAFE_FUNCTIONS _SC_THREAD_SPORADIC_SERVER _SC_THREAD_STACK_MIN _SC_THREAD_THREADS_MAX _SC_THREADS _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_V7_ILP32_OFF32 _SC_V7_ILP32_OFFBIG _SC_V7_LP64_OFF64 _SC_V7_LPBIG_OFFBIG _SC_V6_ILP32_OFF32 _SC_V6_ILP32_OFFBIG _SC_V6_LP64_OFF64 _SC_V6_LPBIG_OFFBIG _SC_VERSION _SC_XOPEN_CRYPT _SC_XOPEN_ENH_I18N _SC_XOPEN_REALTIME _SC_XOPEN_REALTIME_THREADS _SC_XOPEN_SHM _SC_XOPEN_STREAMS _SC_XOPEN_UNIX _SC_XOPEN_UUCP _SC_XOPEN_VERSION .fi .P The two constants _SC_PAGESIZE and _SC_PAGE_SIZE may be defined to have the same value. .P The .IR header shall define the following symbolic constants for file streams: .IP STDERR_FILENO 14 File number of .IR stderr ; 2. .IP STDIN_FILENO 14 File number of .IR stdin ; 0. .IP STDOUT_FILENO 14 File number of .IR stdout ; 1. .P The .IR header shall define the following symbolic constant for terminal special character handling: .IP _POSIX_VDISABLE 14 This symbol shall be defined to be the value of a character that shall disable terminal special character handling as described in .IR "Section 11.2.6" ", " "Special Control Characters". This symbol shall always be set to a value other than \(mi1. .SS "Type Definitions" .P The .IR header shall define the .BR size_t , .BR ssize_t , .BR uid_t , .BR gid_t , .BR off_t , and .BR pid_t types as described in .IR . .P The .IR header shall define the .BR intptr_t type as described in .IR . .SS "Declarations" .P The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. .sp .RS 4 .nf \fB int access(const char *, int); unsigned alarm(unsigned); int chdir(const char *); int chown(const char *, uid_t, gid_t); int close(int); size_t confstr(int, char *, size_t); char *crypt(const char *, const char *); int dup(int); .br int dup2(int, int); void _exit(int); void encrypt(char [64], int); int execl(const char *, const char *, ...); int execle(const char *, const char *, ...); int execlp(const char *, const char *, ...); int execv(const char *, char *const []); int execve(const char *, char *const [], char *const []); int execvp(const char *, char *const []); int faccessat(int, const char *, int, int); int fchdir(int); int fchown(int, uid_t, gid_t); int fchownat(int, const char *, uid_t, gid_t, int); int fdatasync(int); int fexecve(int, char *const [], char *const []); pid_t fork(void); long fpathconf(int, int); int fsync(int); int ftruncate(int, off_t); char *getcwd(char *, size_t); gid_t getegid(void); uid_t geteuid(void); gid_t getgid(void); int getgroups(int, gid_t []); long gethostid(void); int gethostname(char *, size_t); char *getlogin(void); int getlogin_r(char *, size_t); int getopt(int, char * const [], const char *); pid_t getpgid(pid_t); pid_t getpgrp(void); pid_t getpid(void); pid_t getppid(void); pid_t getsid(pid_t); uid_t getuid(void); int isatty(int); int lchown(const char *, uid_t, gid_t); int link(const char *, const char *); int linkat(int, const char *, int, const char *, int); int lockf(int, int, off_t); off_t lseek(int, off_t, int); int nice(int); long pathconf(const char *, int); int pause(void); int pipe(int [2]); ssize_t pread(int, void *, size_t, off_t); ssize_t pwrite(int, const void *, size_t, off_t); ssize_t read(int, void *, size_t); ssize_t readlink(const char *restrict, char *restrict, size_t); ssize_t readlinkat(int, const char *restrict, char *restrict, size_t); int rmdir(const char *); int setegid(gid_t); int seteuid(uid_t); int setgid(gid_t); .br int setpgid(pid_t, pid_t); pid_t setpgrp(void); int setregid(gid_t, gid_t); int setreuid(uid_t, uid_t); pid_t setsid(void); int setuid(uid_t); unsigned sleep(unsigned); void swab(const void *restrict, void *restrict, ssize_t); int symlink(const char *, const char *); int symlinkat(const char *, int, const char *); void sync(void); long sysconf(int); pid_t tcgetpgrp(int); int tcsetpgrp(int, pid_t); int truncate(const char *, off_t); char *ttyname(int); int ttyname_r(int, char *, size_t); int unlink(const char *); int unlinkat(int, const char *, int); ssize_t write(int, const void *, size_t); .fi \fR .P .RE .P Implementations may also include the \fIpthread_atfork\fR() prototype as defined in .IR . Implementations may also include the \fIctermid\fR() prototype as defined in .IR . .P The .IR header shall declare the following external variables: .sp .RS 4 .nf \fB extern char *optarg; extern int opterr, optind, optopt; .fi \fR .P .RE .LP .IR "The following sections are informative." .SH "APPLICATION USAGE" POSIX.1\(hy2008 only describes the behavior of systems that claim conformance to it. However, application developers who want to write applications that adapt to other versions of this standard (or to systems that do not conform to any POSIX standard) may find it useful to code them so as to conditionally compile different code depending on the value of _POSIX_VERSION, for example: .sp .RS 4 .nf \fB #if _POSIX_VERSION >= 200112L /* Use the newer function that copes with large files. */ off_t pos=ftello(fp); #else /* Either this is an old version of POSIX, or _POSIX_VERSION is not even defined, so use the traditional function. */ long pos=ftell(fp); #endif .fi \fR .P .RE .P Earlier versions of POSIX.1\(hy2008 and of the Single UNIX Specification can be identified by the following macros: .IP "POSIX.1\(hy1988 standard" 6 .br _POSIX_VERSION\|=\^=\|198808L .IP "POSIX.1\(hy1990 standard" 6 .br _POSIX_VERSION\|=\^=\|199009L .IP "ISO\ POSIX\(hy1:\|1996 standard" 6 .br _POSIX_VERSION\|=\^=\|199506L .IP "Single UNIX Specification, Version 1" 6 .br _XOPEN_UNIX and _XOPEN_VERSION\|=\^=\|4 .IP "Single UNIX Specification, Version 2" 6 .br _XOPEN_UNIX and _XOPEN_VERSION\|=\^=\|500 .IP "ISO POSIX\(hy1:\|2001 and Single UNIX Specification, Version 3" 6 .br _POSIX_VERSION\|=\^=\|200112L, plus (if the XSI option is supported) _XOPEN_UNIX and _XOPEN_VERSION\|=\^=\|600 .P POSIX.1\(hy2008 does not make any attempt to define application binary interaction with the underlying operating system. However, application developers may find it useful to query _SC_VERSION at runtime via \fIsysconf\fR() to determine whether the current version of the operating system supports the necessary functionality as in the following program fragment: .sp .RS 4 .nf \fB if (sysconf(_SC_VERSION) < 200809L) { fprintf(stderr, "POSIX.1-2008 system required, terminating \en"); exit(1); } .fi \fR .P .RE .P New applications should not use _XOPEN_SHM or _XOPEN_ENH_I18N. .SH RATIONALE As POSIX.1\(hy2008 evolved, certain options became sufficiently standardized that it was concluded that simply requiring one of the option choices was simpler than retaining the option. However, for backwards-compatibility, the option flags (with required constant values) are retained. .SS "Version Test Macros" .P The standard developers considered altering the definition of _POSIX_VERSION and removing _SC_VERSION from the specification of \fIsysconf\fR() since the utility to an application was deemed by some to be minimal, and since the implementation of the functionality is potentially problematic. However, they recognized that support for existing application binaries is a concern to manufacturers, application developers, and the users of implementations conforming to POSIX.1\(hy2008. .P While the example using _SC_VERSION in the APPLICATION USAGE section does not provide the greatest degree of imaginable utility to the application developer or user, it is arguably better than a .BR core file or some other equally obscure result. (It is also possible for implementations to encode and recognize application binaries compiled in various POSIX.1-conforming environments, and modify the semantics of the underlying system to conform to the expectations of the application.) For the reasons outlined in the preceding paragraphs and in the APPLICATION USAGE section, the standard developers elected to retain the _POSIX_VERSION and _SC_VERSION functionality. .SS "Compile-Time Symbolic Constants for System-Wide Options" .P POSIX.1\(hy2008 includes support in certain areas for the newly adopted policy governing options and stubs. .P This policy provides flexibility for implementations in how they support options. It also specifies how conforming applications can adapt to different implementations that support different sets of options. It allows the following: .IP " 1." 4 If an implementation has no interest in supporting an option, it does not have to provide anything associated with that option beyond the announcement that it does not support it. .IP " 2." 4 An implementation can support a partial or incompatible version of an option (as a non-standard extension) as long as it does not claim to support the option. .IP " 3." 4 An application can determine whether the option is supported. A strictly conforming application must check this announcement mechanism before first using anything associated with the option. .P There is an important implication of this policy. POSIX.1\(hy2008 cannot dictate the behavior of interfaces associated with an option when the implementation does not claim to support the option. In particular, it cannot require that a function associated with an unsupported option will fail if it does not perform as specified. However, this policy does not prevent a standard from requiring certain functions to always be present, but that they shall always fail on some implementations. The \fIsetpgid\fR() function in the POSIX.1\(hy1990 standard, for example, is considered appropriate. .P The POSIX standards include various options, and the C-language binding support for an option implies that the implementation must supply data types and function interfaces. An application must be able to discover whether the implementation supports each option. .P Any application must consider the following three cases for each option: .IP " 1." 4 Option never supported. .RS 4 .P The implementation advertises at compile time that the option will never be supported. In this case, it is not necessary for the implementation to supply any of the data types or function interfaces that are provided only as part of the option. The implementation might provide data types and functions that are similar to those defined by POSIX.1\(hy2008, but there is no guarantee for any particular behavior. .RE .IP " 2." 4 Option always supported. .RS 4 .P The implementation advertises at compile time that the option will always be supported. In this case, all data types and function interfaces shall be available and shall operate as specified. .RE .IP " 3." 4 Option might or might not be supported. .RS 4 .P Some implementations might not provide a mechanism to specify support of options at compile time. In addition, the implementation might be unable or unwilling to specify support or non-support at compile time. In either case, any application that might use the option at runtime must be able to compile and execute. The implementation must provide, at compile time, all data types and function interfaces that are necessary to allow this. In this situation, there must be a mechanism that allows the application to query, at runtime, whether the option is supported. If the application attempts to use the option when it is not supported, the result is unspecified unless explicitly specified otherwise in POSIX.1\(hy2008. .RE .SH "FUTURE DIRECTIONS" None. .SH "SEE ALSO" .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP", .IR "\fB\fP" .P .ad l The System Interfaces volume of POSIX.1\(hy2008, .IR "\fIaccess\fR\^(\|)", .IR "\fIalarm\fR\^(\|)", .IR "\fIchown\fR\^(\|)", .IR "\fIclose\fR\^(\|)", .IR "\fIconfstr\fR\^(\|)", .IR "\fIcrypt\fR\^(\|)", .IR "\fIctermid\fR\^(\|)", .IR "\fIdup\fR\^(\|)", .IR "\fI_Exit\fR\^(\|)", .IR "\fIencrypt\fR\^(\|)", .IR "\fIexec\fR\^", .IR "\fIfchdir\fR\^(\|)", .IR "\fIfchown\fR\^(\|)", .IR "\fIfdatasync\fR\^(\|)", .IR "\fIfork\fR\^(\|)", .IR "\fIfpathconf\fR\^(\|)", .IR "\fIfsync\fR\^(\|)", .IR "\fIftruncate\fR\^(\|)", .IR "\fIgetcwd\fR\^(\|)", .IR "\fIgetegid\fR\^(\|)", .IR "\fIgeteuid\fR\^(\|)", .IR "\fIgetgid\fR\^(\|)", .IR "\fIgetgroups\fR\^(\|)", .IR "\fIgethostid\fR\^(\|)", .IR "\fIgethostname\fR\^(\|)", .IR "\fIgetlogin\fR\^(\|)", .IR "\fIgetopt\fR\^(\|)", .IR "\fIgetpgid\fR\^(\|)", .IR "\fIgetpgrp\fR\^(\|)", .IR "\fIgetpid\fR\^(\|)", .IR "\fIgetppid\fR\^(\|)", .IR "\fIgetsid\fR\^(\|)", .IR "\fIgetuid\fR\^(\|)", .IR "\fIisatty\fR\^(\|)", .IR "\fIlchown\fR\^(\|)", .IR "\fIlink\fR\^(\|)", .IR "\fIlockf\fR\^(\|)", .IR "\fIlseek\fR\^(\|)", .IR "\fInice\fR\^(\|)", .IR "\fIpause\fR\^(\|)", .IR "\fIpipe\fR\^(\|)", .IR "\fIread\fR\^(\|)", .IR "\fIreadlink\fR\^(\|)", .IR "\fIrmdir\fR\^(\|)", .IR "\fIsetegid\fR\^(\|)", .IR "\fIseteuid\fR\^(\|)", .IR "\fIsetgid\fR\^(\|)", .IR "\fIsetpgid\fR\^(\|)", .IR "\fIsetpgrp\fR\^(\|)", .IR "\fIsetregid\fR\^(\|)", .IR "\fIsetreuid\fR\^(\|)", .IR "\fIsetsid\fR\^(\|)", .IR "\fIsetuid\fR\^(\|)", .IR "\fIsleep\fR\^(\|)", .IR "\fIswab\fR\^(\|)", .IR "\fIsymlink\fR\^(\|)", .IR "\fIsync\fR\^(\|)", .IR "\fIsysconf\fR\^(\|)", .IR "\fItcgetpgrp\fR\^(\|)", .IR "\fItcsetpgrp\fR\^(\|)", .IR "\fItruncate\fR\^(\|)", .IR "\fIttyname\fR\^(\|)", .IR "\fIunlink\fR\^(\|)", .IR "\fIwrite\fR\^(\|)" .ad b .SH COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .