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Printf (Unix)
printf is a shell command that formats and outputs text like the same-named C function. It is available in a variety of Unix and Unix-like systems. Some shells implement the command as builtin and some provide it as a utility program The command has similar syntax and semantics as the library function. The command outputs text to standard output as specified by a format string and a list of values. Characters of the format string are copied to the output verbatim except when a format specifier is found which causes a value to be output per the specifier. The command has some aspects unlike the library function. In addition to the library function format specifiers, %b causes the command to expand backslash escape sequences (for example \n for newline), and %q outputs an item that can be used as shell input. The value used for an unmatched specifier (too few values) is an empty string for or 0 for a numeric specifier. If there are more values than specifiers, then the comma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open-source Software
Open-source software (OSS) is Software, computer software that is released under a Open-source license, license in which the copyright holder grants users the rights to use, study, change, and Software distribution, distribute the software and its source code to anyone and for any purpose. Open-source software may be developed in a collaborative, public manner. Open-source software is a prominent example of open collaboration, meaning any capable user is able to online collaboration, participate online in development, making the number of possible contributors indefinite. The ability to examine the code facilitates public trust in the software. Open-source software development can bring in diverse perspectives beyond those of a single company. A 2024 estimate of the value of open-source software to firms is $8.8 trillion, as firms would need to spend 3.5 times the amount they currently do without the use of open source software. Open-source code can be used for studying and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syntax (programming Languages)
In computer science, the syntax of a computer language is the rules that define the combinations of symbols that are considered to be correctly structured Statement (computer science), statements or Expression (computer science), expressions in that language. This applies both to programming languages, where the document represents source code, and to markup languages, where the document represents data. The syntax of a language defines its surface form. Text-based user interface, Text-based computer languages are based on sequences of Character (computing), characters, while visual programming languages are based on the spatial layout and connections between symbols (which may be textual or graphical). Documents that are syntactically invalid are said to have a syntax error. When designing the syntax of a language, a designer might start by writing down examples of both legal and illegal String (computer science), strings, before trying to figure out the general rules from these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Core Utilities
The GNU Core Utilities or coreutils is a collection of GNU software that implements many standard, Unix-based shell commands. The utilities generally provide POSIX compliant interface when the environment variable is set, but otherwise offers a superset to the standard interface. For example, the utilities support long options and options after parameters. This environment variable enables a different functionality in BSD. Similar collections are available in the FOSS ecosystem, with a slightly different scope and focus (less functionality), or license. For example, BusyBox which is licensed under GPL-2.0-only, and Toybox which is licensed under 0BSD. Commands The commands implemented by coreutils are listed below. Throughout this article and customary for Unix-based systems, the term ''file'' refers to all file system items including regular files and special files such as directories. File utilities * chcon Changes file security context ( SELinux) * chgrp Chan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley Software Distribution
The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley, beginning in 1978. It began as an improved derivative of AT&T's original Unix that was developed at Bell Labs, based on the source code but over time diverging into its own code. BSD would become a pioneer in the advancement of Unix and computing. BSD's development was begun initially by Bill Joy, who added virtual memory capability to Unix running on a VAX-11 computer. In the 1980s, BSD was widely adopted by workstation vendors in the form of proprietary Unix distributions such as DEC Ultrix and Sun Microsystems SunOS due to its permissive licensing and familiarity to many technology company founders and engineers. It also became the most popular Unix at universities, where it was used for the study of operating systems. BSD was sponsored ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Unix Specification
The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, and user commands. The core specifications of the SUS known as ''Base Specifications'' are developed and maintained by the Austin Group, which is a joint working group of IEEE, ISO/IEC JTC 1/SC 22/WG 15 and The Open Group. If an operating system is submitted to The Open Group for certification and passes conformance tests, then it is deemed to be compliant with a UNIX standard such as UNIX 98 or UNIX 03. Very few BSD and Linux-based operating systems are submitted for compliance with the Single UNIX Specification, although system developers generally aim for compliance with POSIX standards, which form the core of the Single UNIX Specification. The latest SUS consists of two parts: the ''base specifications'' technically iden ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X/Open
X/Open group (also known as the Open Group for Unix Systems and incorporated in 1987 as X/Open Company, Ltd.) was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of information technology. More specifically, the original aim was to define a single specification for operating systems derived from UNIX, to increase the interoperability of applications and reduce the cost of porting software. Its original members were Bull, ICL, Siemens, Olivetti, and Nixdorf—a group sometimes referred to as BISON. Philips and Ericsson joined in 1985, at which point the name X/Open was adopted. The group published its specifications as X/Open Portability Guide, starting with Issue 1 in 1985, and later as ''X/Open CAE Specification''. In 1987, X/Open was incorporated as X/Open Company, Ltd. By March 1988, X/Open grew to 13 members: AT&T, Digital, Hewlett-Packard, Sun Microsystems, Unisys, NCR, Olivetti, Bull, Ericsso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell (computing)
An operating system shell is a computer program that provides relatively broad and direct access to the system on which it runs. The term ''shell'' refers to how it is a relatively thin Abstraction layer, layer around an operating system. A shell is generally a command-line interface (CLI) program although some graphical user interface (GUI) programs are arguably classified as shells too. Overview Operating systems provide various services to their users, including File manager, file management, Process (computing), process management (running and terminating Application program, applications), batch processing, and operating system monitoring and configuration. Most operating system shells are not ''direct'' interfaces to the underlying Kernel (operating system), kernel, even if a shell communicates with the user via peripheral devices attached to the computer directly. Shells are actually special applications that use the kernel API in just the same way as it is used by ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newline
A newline (frequently called line ending, end of line (EOL), next line (NEL) or line break) is a control character or sequence of control characters in character encoding specifications such as ASCII, EBCDIC, Unicode, etc. This character, or a sequence of characters, is used to signify the end of a line (text file), line of text and the start of a new one. History In the mid-1800s, long before the advent of teleprinters and teletype machines, Morse code operators or telegraphists invented and used Prosigns for Morse code, Morse code prosigns to encode white space text formatting in formal written text messages. In particular, the International Morse code, Morse prosign (mnemonic break text), represented by the concatenation of literal textual Morse codes "B" and "T" characters, sent without the normal inter-character spacing, is used in Morse code to encode and indicate a ''new line'' or ''new section'' in a formal text message. Later, in the age of modern teleprinters, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escape Sequence
In computer science, an escape sequence is a combination of characters that has a meaning other than the literal characters contained therein; it is marked by one or more preceding (and possibly terminating) characters. Examples * In C and many derivative programming languages, a string escape sequence is a series of two or more characters, starting with a backslash \. ** Note that in C a backslash immediately followed by a newline does not constitute an escape sequence, but splices physical source lines into logical ones in the second translation phase, whereas string escape sequences are converted in the fifth translation phase. ** To represent the backslash character itself, \\ can be used, whereby the first backslash indicates an escape and the second specifies that a backslash is being escaped. ** A character may be escaped in multiple different ways. Assuming ASCII encoding, the escape sequences \x5c (hexadecimal), \\, and \134 (octal) all encode the same character: the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Character (computing)
In computing and telecommunications, a character is the internal representation of a character (symbol) used within a computer or system. Examples of characters include letters, numerical digits, punctuation marks (such as "." or "-"), and whitespace. The concept also includes control characters, which do not correspond to visible symbols but rather to instructions to format or process the text. Examples of control characters include carriage return and tab as well as other instructions to printers or other devices that display or otherwise process text. Characters are typically combined into '' strings''. Historically, the term ''character'' was used to denote a specific number of contiguous bits. While a character is most commonly assumed to refer to 8 bits (one byte) today, other options like the 6-bit character code were once popular, and the 5-bit Baudot code has been used in the past as well. The term has even been applied to 4 bits with only 16 possible valu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Output
Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object that bears a defined relationship to a unit of measure used for calibration of measuring devices * Standard (timber unit), an obsolete measure of timber used in trade * Breed standard (also called bench standard), in animal fancy and animal husbandry * BioCompute Standard, a standard for next generation sequencing * ''De facto'' standard, product or system with market dominance * Gold standard, a monetary system based on gold; also used metaphorically for the best of several options, against which the others are measured * Internet Standard, a specification ratified as an open standard by the Internet Engineering Task Force * Learning standards, standards applied to education content * Standard displacement, a naval term describing th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semantics (computer Science)
In programming language theory, semantics is the rigorous mathematical study of the meaning of programming languages. Semantics assigns computational meaning to valid strings in a programming language syntax. It is closely related to, and often crosses over with, the semantics of mathematical proofs. Semantics describes the processes a computer follows when executing a program in that specific language. This can be done by describing the relationship between the input and output of a program, or giving an explanation of how the program will be executed on a certain platform, thereby creating a model of computation. History In 1967, Robert W. Floyd published the paper ''Assigning meanings to programs''; his chief aim was "a rigorous standard for proofs about computer programs, including proofs of correctness, equivalence, and termination". Floyd further wrote: A semantic definition of a programming language, in our approach, is founded on a syntactic definition. It mu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
