Misplaced Pages

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81-493: With Windows File Protection active, replacing or deleting a system file that has no file lock to prevent it getting overwritten causes Windows immediately and silently to restore the original copy of the file. The original version of the file is restored from a cached folder which contains backup copies of these files. The Windows NT family uses the cached folder %SystemRoot%\System32\Dllcache . Windows Me caches its entire set of compressed cabinet setup files and stores them in

162-418: A Unix domain socket is implementation dependent. One source of lock failure occurs when buffered I/O has buffers assigned in the user's local workspace, rather than in an operating system buffer pool. fread and fwrite are commonly used to do buffered I/O, and once a section of a file is read, another attempt to read that same section will, most likely, obtain the data from the local buffer. The problem

243-544: A procedural language such as Lua could consist primarily of basic routines to execute code, manipulate data or handle errors while an API for an object-oriented language , such as Java, would provide a specification of classes and its class methods . Hyrum's law states that "With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody." Meanwhile, several studies show that most applications that use an API tend to use

324-420: A software framework : a framework can be based on several libraries implementing several APIs, but unlike the normal use of an API, the access to the behavior built into the framework is mediated by extending its content with new classes plugged into the framework itself. Moreover, the overall program flow of control can be out of the control of the caller and in the framework's hands by inversion of control or

405-449: A broad term describing much of the communication on the internet. When used in this way, the term API has overlap in meaning with the term communication protocol . The interface to a software library is one type of API. The API describes and prescribes the "expected behavior" (a specification) while the library is an "actual implementation" of this set of rules. A single API can have multiple implementations (or none, being abstract) in

486-517: A business ecosystem. The main policies for releasing an API are: An important factor when an API becomes public is its "interface stability". Changes to the API—for example adding new parameters to a function call—could break compatibility with the clients that depend on that API. When parts of a publicly presented API are subject to change and thus not stable, such parts of a particular API should be documented explicitly as "unstable". For example, in

567-460: A client would need to know for practical purposes. Documentation is crucial for the development and maintenance of applications using the API. API documentation is traditionally found in documentation files but can also be found in social media such as blogs, forums, and Q&A websites. Traditional documentation files are often presented via a documentation system, such as Javadoc or Pydoc, that has

648-481: A computer user either by using Windows security, NTFS permissions or by installing a third party file locking software. IBM pioneered file locking in 1963 for use in mainframe computers using OS/360 , where it was termed "exclusive control". Microsoft Windows uses three distinct mechanisms to manage access to shared files: Windows inherits the semantics of share-access controls from the MS-DOS system, where sharing

729-435: A consistent appearance and structure. However, the types of content included in the documentation differs from API to API. In the interest of clarity, API documentation may include a description of classes and methods in the API as well as "typical usage scenarios, code snippets, design rationales, performance discussions, and contracts", but implementation details of the API services themselves are usually omitted. It can take

810-414: A field in place may be permitted under shared access, whereas garbage-collecting and rewriting the database may require exclusive access. File locks apply to the actual file, rather than the file name. This is important since Unix allows multiple names to refer to the same file. Together with non-mandatory locking, this leads to great flexibility in accessing files from multiple processes. On the other hand,

891-471: A file, they may be named more arbitrarily. An unlocker is a utility used to determine what process is locking a file, and displays a list of processes as well as choices on what to do with the process (kill task, unlock, etc.) along with a list of file options such as delete or rename. Their purpose is to remove improper or stale file locks, which often arise from anomalous situations, such as crashed or hung processes, that lead to file locks that persist despite

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972-534: A given API, it is possible to infer the typical usages, as well the required contracts and directives. Then, templates can be used to generate natural language from the mined data. In 2010, Oracle Corporation sued Google for having distributed a new implementation of Java embedded in the Android operating system. Google had not acquired any permission to reproduce the Java API, although permission had been given to

1053-581: A lock on a file (or directory) can be acquired using the Lock function (in the dos.library ). A lock can be shared (other processes can read the file/directory, but can't modify or delete it), or exclusive so that only the process which successfully acquires the lock can access or modify the object. The lock is on the whole object and not part of it. The lock must be released with the UnLock function: unlike in Unix,

1134-399: A lock, the process must verify that the lock file does not exist and then create it, whilst preventing another process from creating it in the meantime. Various methods to do this include: Lock files are often named with a tilde ( ~ ) prefixed to the name of the file they are locking, or a duplicate of the full file name suffixed with .LCK  . If they are locking a resource other than

1215-441: A modular software library in the 1940s for EDSAC , an early computer. The subroutines in this library were stored on punched paper tape organized in a filing cabinet . This cabinet also contained what Wilkes and Wheeler called a "library catalog" of notes about each subroutine and how to incorporate it into a program. Today, such a catalog would be called an API (or an API specification or API documentation) because it instructs

1296-417: A new software product. The process of joining is called integration . As an example, consider a weather sensor that offers an API. When a certain message is transmitted to the sensor, it will detect the current weather conditions and reply with a weather report. The message that activates the sensor is an API call , and the weather report is an API response . A weather forecasting app might integrate with

1377-470: A number of forms, including instructional documents, tutorials, and reference works. It'll also include a variety of information types, including guides and functionalities. Restrictions and limitations on how the API can be used are also covered by the documentation. For instance, documentation for an API function could note that its parameters cannot be null, that the function itself is not thread safe . Because API documentation tends to be comprehensive, it

1458-414: A number of weather sensor APIs, gathering weather data from throughout a geographical area. An API is often compared to a contract . It represents an agreement between parties: a service provider who offers the API and the software developers who rely upon it. If the API remains stable, or if it changes only in predictable ways, developers' confidence in the API will increase. This may increase their use of

1539-440: A programmer on how to use (or "call") each subroutine that the programmer needs. Wilkes and Wheeler's book The Preparation of Programs for an Electronic Digital Computer contains the first published API specification. Joshua Bloch considers that Wilkes and Wheeler "latently invented" the API, because it is more of a concept that is discovered than invented. The term "application program interface" (without an -ing suffix)

1620-518: A programmer will find useful and keeping them consistent even if the internal details later change. An API may be custom-built for a particular pair of systems, or it may be a shared standard allowing interoperability among many systems. The term API is often used to refer to web APIs , which allow communication between computers that are joined by the internet . There are also APIs for programming languages , software libraries , computer operating systems , and computer hardware . APIs originated in

1701-413: A shared lock. To acquire a shared lock, a process must wait until no processes hold any exclusive locks. To acquire an exclusive lock, a process must wait until no processes hold either kind of lock. Unlike locks created by fcntl , those created by flock are preserved across fork s, making them useful in forking servers. It is therefore possible for more than one process to hold an exclusive lock on

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1782-643: A shipping company API that can be added to an eCommerce-focused website to facilitate ordering shipping services and automatically include current shipping rates, without the site developer having to enter the shipper's rate table into a web database. While "web API" historically has been virtually synonymous with web service , the recent trend (so-called Web 2.0 ) has been moving away from Simple Object Access Protocol ( SOAP ) based web services and service-oriented architecture (SOA) towards more direct representational state transfer (REST) style web resources and resource-oriented architecture (ROA). Part of this trend

1863-404: A similar mechanism. An API can specify the interface between an application and the operating system . POSIX , for example, specifies a set of common APIs that aim to enable an application written for a POSIX conformant operating system to be compiled for another POSIX conformant operating system. Linux and Berkeley Software Distribution are examples of operating systems that implement

1944-441: A small part of the API. Language bindings are also APIs. By mapping the features and capabilities of one language to an interface implemented in another language, a language binding allows a library or service written in one language to be used when developing in another language. Tools such as SWIG and F2PY, a Fortran -to- Python interface generator, facilitate the creation of such interfaces. An API can also be related to

2025-463: A software system, used for machine-to-machine communication. A well-designed API exposes only objects or actions needed by software or software developers. It hides details that have no use. This abstraction simplifies programming. Building software using APIs has been compared to using building-block toys, such as Lego bricks. Software services or software libraries are analogous to the bricks; they may be joined together via their APIs, composing

2106-469: Is fcntl . Two other such mechanisms are flock(2) and lockf(3) , each of which may be implemented atop fcntl or may be implemented separately from fcntl . Although some types of locks can be configured to be mandatory, file locks under Unix are by default advisory . This means that cooperating processes may use locks to coordinate access to a file among themselves, but uncooperative processes are also free to ignore locks and access

2187-454: Is a challenge for writers to keep the documentation updated and for users to read it carefully, potentially yielding bugs. API documentation can be enriched with metadata information like Java annotations . This metadata can be used by the compiler, tools, and by the run-time environment to implement custom behaviors or custom handling. It is possible to generate API documentation in a data-driven manner. By observing many programs that use

2268-512: Is an architectural approach that revolves around providing a program interface to a set of services to different applications serving different types of consumers. When used in the context of web development , an API is typically defined as a set of specifications, such as Hypertext Transfer Protocol (HTTP) request messages, along with a definition of the structure of response messages, usually in an Extensible Markup Language ( XML ) or JavaScript Object Notation ( JSON ) format. An example might be

2349-417: Is another user attached to the same file has their own local buffers, and the same thing is happening for them. An fwrite of data obtained from the buffer by fread will not be obtaining the data from the file itself, and some other user could have changed it. Both could use flock to ensure exclusive access, which prevents simultaneous writes, but since the reads are reading from the buffer and not

2430-433: Is closed by that process, even if a lock was never requested for that file descriptor. Also, fcntl locks are not inherited by a child process. The fcntl close semantics are particularly troublesome for applications that call subroutine libraries that may access files. Neither of these "bugs" occurs using real flock -style locks. Preservation of the lock status on open file descriptors passed to another process using

2511-522: Is created in one place dynamically can be posted and updated to multiple locations on the web. For example, Twitter's REST API allows developers to access core Twitter data and the Search API provides methods for developers to interact with Twitter Search and trends data. The design of an API has significant impact on its usage. The principle of information hiding describes the role of programming interfaces as enabling modular programming by hiding

Windows File Protection - Misplaced Pages Continue

2592-481: Is determined by the dwFlags parameter in the LockFileEx function used to lock a region of a file. The Windows API function LockFile can also be used and acquires an exclusive lock on the region of the file. Any file containing an executable program file that is currently running on the computer system as a program (e.g. an EXE , COM , DLL , CPL or other binary program file format)

2673-399: Is first recorded in a paper called Data structures and techniques for remote computer graphics presented at an AFIPS conference in 1968. The authors of this paper use the term to describe the interaction of an application—a graphics program in this case—with the rest of the computer system. A consistent application interface (consisting of Fortran subroutine calls) was intended to free

2754-490: Is locked. A lock file is often the best approach if the resource to be controlled is not a regular file at all, so using methods for locking files does not apply. For example, a lock file might govern access to a set of related resources, such as several different files, directories, a group of disk partitions, or selected access to higher level protocols like servers or database connections. When using lock files, care must be taken to ensure that operations are atomic . To obtain

2835-551: Is normally locked by the operating system itself, preventing any application from modifying or deleting it. Any attempt to do so will be denied with a sharing violation error, despite the fact that the program file is not opened by any application. However, some access is still allowed. For example, a running application file can be renamed or copied (read) even when executing. Files are accessed by applications in Windows by using file handles . These file handles can be explored with

2916-453: Is now the most common meaning of the term API. The Semantic Web proposed by Tim Berners-Lee in 2001 included "semantic APIs" that recast the API as an open , distributed data interface rather than a software behavior interface. Proprietary interfaces and agents became more widespread than open ones, but the idea of the API as a data interface took hold. Because web APIs are widely used to exchange data of all kinds online, API has become

2997-475: Is related to the Semantic Web movement toward Resource Description Framework (RDF), a concept to promote web-based ontology engineering technologies. Web APIs allow the combination of multiple APIs into new applications known as mashups . In the social media space, web APIs have allowed web communities to facilitate sharing content and data between communities and applications. In this way, content that

3078-726: Is rewritten to specifically support this feature, the snapshot will be crash consistent only, while properly supported applications can assist the operating system in creating "transactionally consistent" snapshots. Other commercial software for accessing locked files under Windows include File Access Manager and Open File Manager . These work by installing their own drivers to access the files in kernel mode . Unix-like operating systems (including Linux and Apple's macOS ) do not normally automatically lock open files. Several kinds of file-locking mechanisms are available in different flavors of Unix, and many operating systems support more than one kind for compatibility. The most common mechanism

3159-417: Is used to prevent two users changing the same file version in parallel and then when saving, the second user to overwrite what first user changed. This is implemented by marking locked files as read-only in the file system. A user wanting to change the file performs an unlock (also called checkout) operation, and until a check-in (store) operation is done, or the lock is reverted, nobody else is allowed to unlock

3240-469: The %windir%\Options\Install folder. WFP covers all files which the operating system installs (such as DLL , EXE , SYS , OCX etc.), protecting them from deletion or from replacement by older versions. The digital signatures of these files are checked using code signing and the signature catalog files stored in the %SystemRoot%\system32\CatRoot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE } folder. Only certain operating system components such as

3321-521: The CreateFile function (used to open files) determines file-sharing. The sharing mode can be specified to allow sharing the file for read, write, or delete access, or any combination of these. Subsequent attempts to open the file must be compatible with all previously granted sharing-access to the file. When the file is closed, sharing-access restrictions are adjusted to remove the restrictions imposed by that specific file open. Byte-range locking type

Windows File Protection - Misplaced Pages Continue

3402-763: The unlink system call. Consequently, certain programs may, effectively, circumvent mandatory locking. Stevens & Rago (2005) observed that the ed editor indeed did that. Whether and how flock locks work on network filesystems, such as NFS , is implementation dependent. On BSD systems, flock calls on a file descriptor open to a file on an NFS-mounted partition are successful no-ops . On Linux prior to 2.6.12, flock calls on NFS files would act only locally. Kernel 2.6.12 and above implement flock calls on NFS files using POSIX byte-range locks. These locks will be visible to other NFS clients that implement fcntl -style POSIX locks , but invisible to those that do not. Lock upgrades and downgrades release

3483-549: The Google Guava library, the parts that are considered unstable, and that might change soon, are marked with the Java annotation @Beta . A public API can sometimes declare parts of itself as deprecated or rescinded. This usually means that part of the API should be considered a candidate for being removed, or modified in a backward incompatible way. Therefore, these changes allow developers to transition away from parts of

3564-686: The Java language in particular. In the 1990s, with the spread of the internet , standards like CORBA , COM , and DCOM competed to become the most common way to expose API services. Roy Fielding 's dissertation Architectural Styles and the Design of Network-based Software Architectures at UC Irvine in 2000 outlined Representational state transfer (REST) and described the idea of a "network-based Application Programming Interface" that Fielding contrasted with traditional "library-based" APIs. XML and JSON web APIs saw widespread commercial adoption beginning in 2000 and continuing as of 2021. The web API

3645-512: The Java remote method invocation API uses the Java Remote Method Protocol to allow invocation of functions that operate remotely, but appear local to the developer. Therefore, remote APIs are useful in maintaining the object abstraction in object-oriented programming ; a method call , executed locally on a proxy object, invokes the corresponding method on the remote object, using the remoting protocol, and acquires

3726-556: The Linux Standard Base provides an ABI. Remote APIs allow developers to manipulate remote resources through protocols , specific standards for communication that allow different technologies to work together, regardless of language or platform. For example, the Java Database Connectivity API allows developers to query many different types of databases with the same set of functions, while

3807-477: The Package Installer (Update.exe) or Windows Installer (Msiexec.exe) can replace these files. Changes made using any other methods in order to replace these files are reverted and the files are silently restored from the cache. If Windows File Protection cannot automatically find the file in the cached folder, it searches the network path or prompts the user for the Windows installation disc to restore

3888-646: The Process Explorer utility. This utility can also be used to force-close handles without needing to terminate the application holding them. This can cause an undefined behavior, since the program will receive an unexpected error when using the force-closed handle and may even operate on an unexpected file since the handle number may be recycled. Microsoft Windows XP and Server 2003 editions have introduced volume snapshot ( VSS ) capability to NTFS , allowing open files to be accessed by backup software despite any exclusive locks. However, unless software

3969-470: The Solaris , HP-UX , and Linux operating systems. It is not part of POSIX, however, and BSD-derived operating systems such as FreeBSD , OpenBSD , NetBSD , and Apple's macOS do not support it. Linux also supports mandatory locking through the special -o mand parameter for file system mounting ( mount(8) ), but this is rarely used. Some Unix-like operating systems prevent attempts to open

4050-417: The 1940s, though the term did not emerge until the 1960s and 70s. An API opens a software system to interactions from the outside. It allows two software systems to communicate across a boundary — an interface — using mutually agreed-upon signals. In other words, an API connects software entities together. Unlike a user interface , an API is typically not visible to users. It is an "under the hood" portion of

4131-461: The API that will be removed or not supported in the future. Client code may contain innovative or opportunistic usages that were not intended by the API designers. In other words, for a library with a significant user base, when an element becomes part of the public API, it may be used in diverse ways. On February 19, 2020, Akamai published their annual “State of the Internet” report, showcasing

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4212-435: The API. The term API initially described an interface only for end-user-facing programs, known as application programs . This origin is still reflected in the name "application programming interface." Today, the term is broader, including also utility software and even hardware interfaces . The idea of the API is much older than the term itself. British computer scientists Maurice Wilkes and David Wheeler worked on

4293-502: The POSIX APIs. Microsoft has shown a strong commitment to a backward-compatible API, particularly within its Windows API (Win32) library, so older applications may run on newer versions of Windows using an executable-specific setting called "Compatibility Mode". An API differs from an application binary interface (ABI) in that an API is source code based while an ABI is binary based. For instance, POSIX provides APIs while

4374-401: The application programming interface separately from other interfaces, such as the query interface. Database professionals in the 1970s observed these different interfaces could be combined; a sufficiently rich application interface could support the other interfaces as well. This observation led to APIs that supported all types of programming, not just application programming. By 1990, the API

4455-639: The appropriate version of the file. WFP integrates with the System File Checker ( sfc.exe ) utility. Windows Vista and later Windows systems do not include Windows File Protection, but they include Windows Resource Protection which protects files using ACLs . Windows Resource Protection aims to protect core registry keys and values and prevent potentially damaging system configuration changes, besides operating system files. The non-use of ACLs in Windows File Protection

4536-404: The cooperative locking approach can lead to problems when a process writes to a file without obeying file locks set by other processes. For this reason, some Unix-like operating systems also offer limited support for mandatory locking . On such systems, a file whose setgid bit is on but whose group execution bit is off when that file is opened will be subject to automatic mandatory locking if

4617-428: The executable file of a running program for writing; this is a third form of locking, separate from those provided by fcntl and flock . More than one process can hold an exclusive flock on a given file if the exclusive lock was duplicated across a later fork . This simplifies coding for network servers and helps prevent race conditions, but can be confusing to the unaware. Mandatory locks have no effect on

4698-454: The file in any way they choose. In other words, file locks lock out other file lockers only, not I/O. Two kinds of locks are offered: shared locks and exclusive locks. In the case of fcntl , different kinds of locks may be applied to different sections (byte ranges) of a file, or else to the whole file. Shared locks can be held by multiple processes at the same time, but an exclusive lock can only be held by one process, and cannot coexist with

4779-441: The file itself, any data changed by user #1 can be lost by user #2 (over-written). The best solution to this problem is to use unbuffered I/O ( read and write ) with flock , which also means using lseek instead of fseek and ftell . Of course, you'll have to make adjustments for function parameters and results returned. Generally speaking, buffered I/O is unsafe when used with shared files. In AmigaOS ,

4860-511: The file systems that execute within Windows. For applications that use the file mapping APIs in Windows, byte-range locks are not enforced (also referred to as advisory locks. ) Byte-range locking may also have other side-effects on the Windows system. For example, the Windows file-sharing mechanism will typically disable client side caching of a file for all clients when byte-range locks are used by any client. The client will observe slower access because read and write operations must be sent to

4941-458: The file while it's being modified or deleted. Systems implement locking to prevent an interceding update scenario, which is an example of a race condition , by enforcing the serialization of update processes to any given file. The following example illustrates the interceding update problem: Most operating systems support the concept of record locking , which means that individual records within any given file may be locked, thereby increasing

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5022-463: The file. API An application programming interface ( API ) is a connection between computers or between computer programs . It is a type of software interface , offering a service to other pieces of software . A document or standard that describes how to build such a connection or interface is called an API specification . A computer system that meets this standard is said to implement or expose an API. The term API may refer either to

5103-441: The file. Such byte-range locks specify a region of the file (offset and length) and the type of lock (shared or exclusive). Note that the region of the file being locked is not required to have data within the file, and applications sometimes exploit this ability to implement their functionality. For applications that use the file read/write APIs in Windows, byte-range locks are enforced (also referred to as mandatory locks ) by

5184-420: The form of different libraries that share the same programming interface. The separation of the API from its implementation can allow programs written in one language to use a library written in another. For example, because Scala and Java compile to compatible bytecode , Scala developers can take advantage of any Java API. API use can vary depending on the type of programming language involved. An API for

5265-476: The growing trend of cybercriminals targeting public API platforms at financial services worldwide. From December 2017 through November 2019, Akamai witnessed 85.42 billion credential violation attacks. About 20%, or 16.55 billion, were against hostnames defined as API endpoints. Of these, 473.5 million have targeted financial services sector organizations. API documentation describes what services an API offers and how to use those services, aiming to cover everything

5346-490: The implementation details of the modules so that users of modules need not understand the complexities inside the modules. Thus, the design of an API attempts to provide only the tools a user would expect. The design of programming interfaces represents an important part of software architecture , the organization of a complex piece of software. APIs are one of the more common ways technology companies integrate. Those that provide and use APIs are considered as being members of

5427-540: The number of concurrent update processes. Database maintenance uses file locking, whereby it can serialize access to the entire physical file underlying a database. Although this does prevent any other process from accessing the file, it can be more efficient than individually locking many regions in the file by removing the overhead of acquiring and releasing each lock. Poor use of file locks, like any computer lock , can result in poor performance or in deadlocks . File locking may also refer to additional security applied by

5508-455: The old lock before applying the new lock. If an application downgrades an exclusive lock to a shared lock while another application is blocked waiting for an exclusive lock, the latter application may get the exclusive lock and lock the first application out. This means that lock downgrades can block, which may be counter-intuitive. All fcntl locks associated with a file for a given process are removed when any file descriptor for that file

5589-420: The operating system does not implicitly unlock the object when the process terminates. Shell scripts and other programs often use a strategy similar to the use of file locking: creation of lock files , which are files whose contents are irrelevant (although often one will find the process identifier of the holder of the lock in the file) and whose sole purpose is to signal by their presence that some resource

5670-440: The owning process having died already. On some Unix-like systems, utilities such as fstat and lockf can be used to inspect the state of file locks by process, by filename, or both. On Windows systems, if a file is locked, it's possible to schedule its moving or deletion to be performed on the next reboot. This approach is typically used by installers to replace locked system files. In version control systems file locking

5751-614: The programmer from dealing with idiosyncrasies of the graphics display device, and to provide hardware independence if the computer or the display were replaced. The term was introduced to the field of databases by C. J. Date in a 1974 paper called The Relational and Network Approaches: Comparison of the Application Programming Interface . An API became a part of the ANSI/SPARC framework for database management systems . This framework treated

5832-416: The programmer. A program or a programmer that uses one of these parts is said to call that portion of the API. The calls that make up the API are also known as subroutines , methods, requests, or endpoints . An API specification defines these calls, meaning that it explains how to use or implement them. One purpose of APIs is to hide the internal details of how a system works, exposing only those parts

5913-442: The result to be used locally as a return value. A modification of the proxy object will also result in a corresponding modification of the remote object. Web APIs are the defined interfaces through which interactions happen between an enterprise and applications that use its assets, which also is a Service Level Agreement (SLA) to specify the functional provider and expose the service path or URL for its API users. An API approach

5994-464: The same file, provided these processes share a filial relationship and the exclusive lock was initially created in a single process before being duplicated across a fork . Shared locks are sometimes called "read locks" and exclusive locks are sometimes called "write locks". However, because locks on Unix are advisory, this isn't enforced. Thus it is possible for a database to have a concept of "shared writes" vs. "exclusive writes"; for example, changing

6075-512: The server where the file is stored. Improper error-handling in an application program can lead to a scenario where a file is locked (either using "share" access or with byte-range file locking) and cannot be accessed by other applications. If so, the user may be able to restore file access by manually terminating the malfunctioning program. This is typically done through the Task Manager utility. The sharing mode (dwShareMode) parameter of

6156-452: The similar OpenJDK project. Judge William Alsup ruled in the Oracle v. Google case that APIs cannot be copyrighted in the U.S. and that a victory for Oracle would have widely expanded copyright protection to a "functional set of symbols" and allowed the copyrighting of simple software commands: To accept Oracle's claim would be to allow anyone to copyright one version of code to carry out

6237-450: The specification or to the implementation. In contrast to a user interface , which connects a computer to a person, an application programming interface connects computers or pieces of software to each other. It is not intended to be used directly by a person (the end user ) other than a computer programmer who is incorporating it into software. An API is often made up of different parts which act as tools or services that are available to

6318-459: The underlying filesystem supports it. However, non-local NFS partitions tend to disregard this bit. If a file is subject to mandatory locking, attempts to read from a region that is locked with an exclusive lock, or to write to a region that is locked with a shared or exclusive lock, will block until the lock is released. This strategy first originated in System ;V, and can be seen today in

6399-403: Was a design choice: Not only did it allow operation on non-NTFS systems, but it prevented those same "bad" installers from failing completely from a file access error. File locking File locking is a mechanism that restricts access to a computer file , or to a region of a file, by allowing only one user or process to modify or delete it at a specific time, and preventing reading of

6480-455: Was defined simply as "a set of services available to a programmer for performing certain tasks" by technologist Carl Malamud . The idea of the API was expanded again with the dawn of remote procedure calls and web APIs . As computer networks became common in the 1970s and 80s, programmers wanted to call libraries located not only on their local computers, but on computers located elsewhere. These remote procedure calls were well supported by

6561-471: Was introduced in MS-DOS ;3.3 . Thus, an application must explicitly allow sharing when it opens a file; otherwise it has exclusive read, write, and delete access to the file until closed (other types of access, such as those to retrieve the attributes of a file are allowed.) For a file opened with shared access, applications may then use byte-range locking to control access to specific regions of

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