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Message Pump
In computer science, the event loop (also known as message dispatcher, message loop, message pump, or run loop) is a programming construct or software design pattern, design pattern that waits for and dispatches event-driven programming, events or Message Passing Interface, messages in a computer program, program. The event loop works by making a request to some internal or external "event provider" (that generally blocking (computing), blocks the request until an event has arrived), then calls the relevant event handler ("dispatches the event"). It is also commonly implemented in servers such as Web server, web servers. The event loop may be used in conjunction with a reactor pattern, reactor, if the event provider follows the #File interface, file interface, which can be selected or 'polled' (the Unix system call, not actual polling (computer science), polling). The event loop almost always operates asynchronously with the message originator. When the event loop forms the centra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interface
A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards. For a long time, a CLI was the most common interface for software, but today a graphical user interface (GUI) is more common. Nonetheless, many programs such as operating system and software development utility software, utilities still provide CLI. A CLI enables automation, automating computer program, programs since commands can be stored in a scripting language, script computer file, file that can be used repeatedly. A script allows its contained commands to be executed as group; as a program; as a command. A CLI is made possible by command-line interpreters or command-line processors, which are programs that execute input commands. Alternatives to a CLI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CPU Bound
A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions of a computer program, such as arithmetic, logic, controlling, and input/output (I/O) operations. This role contrasts with that of external components, such as main memory and I/O circuitry, and specialized coprocessors such as graphics processing units (GPUs). The form, CPU design, design, and implementation of CPUs have changed over time, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic–logic unit (ALU) that performs arithmetic operation, arithmetic and Bitwise operation, logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the #Fetch, fetching (from memory), #Decode, decoding and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Errno
errno.h is a header file in the standard library of the C programming language. It defines macros for reporting and retrieving error conditions using the symbol errno (short form for "error number").International Standard for Programming Language C (C11), ISO/IEC 9899:2011, p. 205 errno acts like an integer variable. A value (the error number) is stored in errno by certain library functions when they detect errors. At program startup, the value stored is zero. Library functions store only values greater than zero. Any library function can alter the value stored before return, whether or not they detect errors.International Standard for Programming Language C (C99), ISO/IEC 9899:1999, p. 186 Most functions indicate that they detected an error by returning a special value, typically NULL for functions that return pointers, and -1 for functions that return integers. A few functions require the caller to preset errno to zero and test it afterwards to see if an error was detected. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal (IPC)
Signals are standardized messages sent to a running program to trigger specific behavior, such as quitting or error handling. They are a limited form of inter-process communication (IPC), typically used in Unix, Unix-like, and other POSIX-compliant operating systems. A signal is an asynchronous notification sent to a process or to a specific thread within the same process to notify it of an event. Common uses of signals are to interrupt, suspend, terminate or kill a process. Signals originated in 1970s Bell Labs Unix and were later specified in the POSIX standard. When a signal is sent, the operating system interrupts the target process's normal flow of execution to deliver the signal. Execution can be interrupted during any non-atomic instruction. If the process has previously registered a signal handler, that routine is executed. Otherwise, the default signal handler is executed. Embedded programs may find signals useful for inter-process communications, as sign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley Sockets
A Berkeley ( BSD) socket is an application programming interface (API) for Internet domain sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated with the 4.2BSD Unix operating system, which was released in 1983. A socket is an abstract representation (handle) for the local endpoint of a network communication path. The Berkeley sockets API represents it as a file descriptor in the Unix philosophy that provides a common interface for input and output to streams of data. Berkeley sockets evolved with little modification from a ''de facto'' standard into a component of the POSIX specification. The term POSIX sockets is essentially synonymous with ''Berkeley sockets'', but they are also known as BSD sockets, acknowledging the first implementation in the Berkeley Software Distribution. History and implementations Berkeley sockets originated with the 4.2BSD Unix operating system, relea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix Domain Socket
A Unix domain socket (UDS), a.k.a. local socket, a.k.a. inter-process communication (IPC) socket, is a communication endpoint for exchanging data between processes executing in the same Unix or Unix-like operating system. The name, ''Unix domain socket'', refers to the domain argument value AF_UNIX that is passed to the function that creates a socket system resource. The same communication domain is also selected by AF_LOCAL. Valid type argument values for a UDS are: * SOCK_STREAM (compare to TCP) – for a stream-oriented socket * SOCK_DGRAM (compare to UDP) – for a datagram-oriented socket that preserves message boundaries (as on most UNIX implementations, UNIX domain datagram sockets are always reliable and don't reorder datagrams) * SOCK_SEQPACKET (compare to SCTP) – for a sequenced-packet socket that is connection-oriented, preserves message boundaries, and delivers messages in the order that they were sent The UDS facility is a standard component of a POSIX operatin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Window System
The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at version 11 (hence "X11") since September 1987. The X.Org Foundation leads the X project, with the current reference implementation, X.Org Server, available as free and open-source software under the MIT License and similar permissive licenses. Purpose and abilities X is an architecture-independent system for remote graphical user interfaces and input device capabilities. Each person using a networked computer terminal, terminal has the ability to interact with the display with any type of user input device. In its standard distribution it is a complete, albeit simple, display and interface solution which delivers a standard widget toolkit, toolkit and protocol stack for building graphical user interfaces on most Unix-like operating syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poll (Unix)
is a POSIX system call to wait for one or more file descriptors to become ready for use. On *BSD and macOS, it has been largely superseded by kqueue in high performance applications. On Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ..., it has been superseded by and . See also * kqueue * epoll * inotify * select References External links * * C POSIX library Events (computing) System calls Unix {{compu-prog-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Select (Unix)
is a system call and application programming interface (API) in Unix-like and POSIX-compliant operating systems for examining the status of file descriptors of open input/output channels. The select system call is similar to the ' facility introduced in UNIX System V and later operating systems. However, with the c10k problem, both select and poll have been superseded by the likes of kqueue, epoll, /dev/poll and I/O completion ports. One common use of select outside of its stated use of waiting on filehandles is to implement a portable sub-second sleep. This can be achieved by passing NULL for all three fd_set arguments, and the duration of the desired sleep as the timeout argument. In the C programming language, the select system call is declared in the header file sys/select.h or unistd.h, and has the following syntax: int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout); fd_set type arguments may be manipulated with fou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Descriptor
In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically have non-negative integer values, with negative values being reserved to indicate "no value" or error conditions. File descriptors are a part of the POSIX API. Each Unix process (except perhaps daemons) should have three standard POSIX file descriptors, corresponding to the three standard streams: Overview In the traditional implementation of Unix, file descriptors index into a per-process maintained by the kernel, that in turn indexes into a system-wide table of files opened by all processes, called the . This table records the ''mode'' with which the file (or other resource) has been opened: for reading, writing, appending, and possibly other modes. It also indexes into a third table called the inode table that describes the ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Everything Is A File
"Everything is a file" is an approach to interface design in Unix derivatives. While this turn of phrase does not as such figure as a Unix design principle or philosophy, it is a common way to analyse designs, and informs the design of new interfaces in a way that prefers, in rough order of import: # representing objects as file descriptors in favour of alternatives like abstract handles or names, # operating on the objects with standard input/output operations returning byte streams to be interpreted by applications (rather than explicitly structured data), and # allowing the usage or creation of objects by opening or creating files in the global filesystem name space. The lines between the common interpretations of "file" and "file descriptor" are often blurred when analysing Unix, and nameability of ''files'' is the least important part of this principle; thus, it is sometimes described as "Everything is a file descriptor". This approach is interpreted differently with time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
