All 64-bit applications can manipulate large files by default. The interfaces described on this page can be used by 32-bit and 64-bit applications to manipulate large files.
In the transitional compilation environment, explicit 64-bit functions, structures, and types are added to the API. Compiling in this environment allows both 32-bit and 64-bit applications to access files whose size is greater than or equal to 2 gigabytes (2**31 bytes).
The transitional compilation environment exports all the explicit 64-bit functions (xxx64()) and types in addition to all the regular functions (xxx()) and types. Both xxx() and xxx64() functions are available to the program source. A 32-bit application must use the xxx64() functions in order to access large files. See the lf64 reference page for a complete listing of the 64-bit transitional interfaces.
The transitional compilation environment differs from the large file compilation environment, wherein the underlying interfaces are bound to 64-bit functions, structures, and types. An application compiled in the large file compilation environment is able to use the xxx() source interfaces to access both large and small files, rather than having to explicitly utilize the transitional xxx64() interface calls to access large files. See the lfcompile reference page for more information regarding the large file compilation environment.
Applications may combine objects produced in the large file compilation environment with objects produced in the transitional compilation environment, but must be careful with respect to interoperability between those objects. Applications should not declare global variables of types whose sizes change between compilation environments.
For applications that do not wish to conform to the POSIX or X/Open specifications, the 64-bit transitional interfaces are available by default. No compile-time flags need to be set.
Applications that wish to access the transitional interfaces as well as
the POSIX or X/Open specification-conforming interfaces should use the
In the following examples, the transitional compilation
environment is accessed by invoking the getconf utility
with one of the arguments listed in the table above. The
additional large file interfaces are accessed by specifying
% c89 -D_LARGEFILE_SOURCE a.c
Large File Specification, revision 1.5.
PTC MKS Toolkit for Professional Developers
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