Codes

The codes and their meanings are as follows. See also Margin Code Notation .

^[ADV] Advisory Information
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the ADV margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the ADV margin legend.

^[BE] Batch Environment Services and Utilities
The functionality described is optional.

Where applicable, utilities are marked with the BE margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the BE margin legend.

^[CD] C-Language Development Utilities
The functionality described is optional.

Where applicable, utilities are marked with the CD margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the CD margin legend.

^[CPT] Process CPU-Time Clocks
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the CPT margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the CPT margin legend.

^[CX] Extension to the ISO C standard
The functionality described is an extension to the ISO C standard. Application developers may make use of an extension as it is supported on all POSIX.1-2017-conforming systems.

With each function or header from the ISO C standard, a statement to the effect that "any conflict is unintentional" is included. That is intended to refer to a direct conflict. POSIX.1-2017 acts in part as a profile of the ISO C standard, and it may choose to further constrain behaviors allowed to vary by the ISO C standard. Such limitations and other compatible differences are not considered conflicts, even if a CX mark is missing. The markings are for information only.

Where additional semantics apply to a function or header, the material is identified by use of the CX margin legend.

^[FD] FORTRAN Development Utilities
The functionality described is optional.

Where applicable, utilities are marked with the FD margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the FD margin legend.

^[FR] FORTRAN Runtime Utilities
The functionality described is optional.

Where applicable, utilities are marked with the FR margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the FR margin legend.

^[FSC] File Synchronization
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the FSC margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the FSC margin legend.

^[IP6] IPV6
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the IP6 margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the IP6 margin legend.

^[MC1] Non-Robust Mutex Priority Protection or Non-Robust Mutex Priority Inheritance or Robust Mutex Priority Protection or Robust Mutex Priority Inheritance
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

This is a shorthand notation for combinations of multiple option codes.

Where applicable, functions are marked with the MC1 margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the MC1 margin legend.

Refer to Margin Code Notation .

^[ML] Process Memory Locking
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the ML margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the ML margin legend.

^[MLR] Range Memory Locking
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the MLR margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the MLR margin legend.

^[MON] Monotonic Clock
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the MON margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the MON margin legend.

^[MSG] Message Passing
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the MSG margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the MSG margin legend.

^[MX] IEC 60559 Floating-Point
The functionality described is optional. The functionality described is mandated by the ISO C standard only for implementations that define __STDC_IEC_559__.

^[MXX] IEC 60559 Floating-Point Extension
The functionality described is optional. The functionality described is part of the IEC 60559 Floating-Point option, but is an extension fo the ISO C standard

^[OB] Obsolescent
The functionality described may be removed in a future version of this volume of POSIX.1-2017. Strictly Conforming POSIX Applications and Strictly Conforming XSI Applications shall not use obsolescent features.

Where applicable, the material is identified by use of the OB margin legend.

^[OF] Output Format Incompletely Specified
The functionality described is an XSI extension. The format of the output produced by the utility is not fully specified. It is therefore not possible to post-process this output in a consistent fashion. Typical problems include unknown length of strings and unspecified field delimiters.

Where applicable, the material is identified by use of the OF margin legend.

^[OH] Optional Header
In the SYNOPSIS section of some interfaces in the System Interfaces volume of POSIX.1-2017 an included header is marked as in the following example:

[OH]
#include <sys/types.h>

#include <grp.h>
struct group *getgrnam(const char *name);

The OH margin legend indicates that the marked header is not required on XSI-conformant systems.

^[PIO] Prioritized Input and Output
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the PIO margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the PIO margin legend.

^[PS] Process Scheduling
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the PS margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the PS margin legend.

^[RPI] Robust Mutex Priority Inheritance
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the RPI margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the RPI margin legend.

^[RPP] Robust Mutex Priority Protection
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the RPP margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the RPP margin legend.

^[RS] Raw Sockets
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the RS margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the RS margin legend.

^[SD] Software Development Utilities
The functionality described is optional.

Where applicable, utilities are marked with the SD margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the SD margin legend.

^[SHM] Shared Memory Objects
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the SHM margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the SHM margin legend.

^[SIO] Synchronized Input and Output
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the SIO margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the SIO margin legend.

^[SPN] Spawn
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the SPN margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the SPN margin legend.

^[SS] Process Sporadic Server
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the SS margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the SS margin legend.

^[TCT] Thread CPU-Time Clocks
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TCT margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TCT margin legend.

^[TEF] Trace Event Filter
The functionality described is optional. This functionality is dependent on support for the Trace option. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TEF margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TEF margin legend.

^[TPI] Non-Robust Mutex Priority Inheritance
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TPI margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TPI margin legend.

^[TPP] Non-Robust Mutex Priority Protection
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TPP margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TPP margin legend.

^[TPS] Thread Execution Scheduling
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TPS margin legend for the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TPS margin legend.

^[TRC] Trace
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TRC margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TRC margin legend.

^[TRI] Trace Inherit
The functionality described is optional. This functionality is dependent on support for the Trace option. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TRI margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TRI margin legend.

^[TRL] Trace Log
The functionality described is optional. This functionality is dependent on support for the Trace option. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TRL margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TRL margin legend.

^[TSA] Thread Stack Address Attribute
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TSA margin legend for the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TSA margin legend.

^[TSH] Thread Process-Shared Synchronization
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TSH margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TSH margin legend.

^[TSP] Thread Sporadic Server
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TSP margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TSP margin legend.

^[TSS] Thread Stack Size Attribute
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TSS margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TSS margin legend.

^[TYM] Typed Memory Objects
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the TYM margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the TYM margin legend.

^[UP] User Portability Utilities
The functionality described is optional.

Where applicable, utilities are marked with the UP margin legend in the SYNOPSIS section. Where additional semantics apply to a utility, the material is identified by use of the UP margin legend.

^[UU] UUCP Utilities
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the UU margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the UU margin legend.

^[XSI] X/Open System Interfaces
The functionality described is part of the X/Open Systems Interfaces option. Functionality marked XSI is an extension to the ISO C standard. Application developers may confidently make use of such extensions on all systems supporting the X/Open System Interfaces option.

If an entire SYNOPSIS section is shaded and marked XSI, all the functionality described in that reference page is an extension. See XSI Conformance .

^[XSR] XSI STREAMS
The functionality described is optional. The functionality described is also an extension to the ISO C standard.

Where applicable, functions are marked with the XSR margin legend in the SYNOPSIS section. Where additional semantics apply to a function, the material is identified by use of the XSR margin legend.

Margin Code Notation

Some of the functionality described in POSIX.1-2017 depends on support of more than one option, or independently may depend on several options. The following notation for margin codes is used to denote the following cases.

A Feature Dependent on One or Two Options

In this case, margin codes have a <space> separator; for example:

^[SHM] This feature requires support for only the Shared Memory Objects option.

^{[SHM TYM]} This feature requires support for both the Shared Memory Objects option and the Typed Memory Objects option; that is, an application which uses this feature is portable only between implementations that provide both options.

A Feature Dependent on Either of the Options Denoted

In this case, margin codes have a '|' separator to denote the logical OR; for example:

^[SHM|TYM] This feature is dependent on support for either the Shared Memory Objects option or the Typed Memory Objects option; that is, an application which uses this feature is portable between implementations that provide any (or all) of the options.

A Feature Dependent on More than Two Options

The following shorthand notations are used:

^[MC1] The MC1 margin code is shorthand for TPP|TPI|RPP|RPI. Features which are shaded with this margin code require support of either the Non-Robust Mutex Priority Protection option or the Non-Robust Mutex Priority Inheritance option or the Robust Mutex Priority Protection option or the Robust Mutex Priority Inheritance option.

Large Sections Dependent on an Option

Where large sections of text are dependent on support for an option, a lead-in text block is provided and shaded accordingly; for example:

^[XSI] This section describes extensions to support interprocess communication. The functionality described in this section shall be provided on implementations that support the XSI option (and the rest of this section is not further marked).