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Shell Scripting
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be command languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text. A script which sets up the environment, runs the program, and does any necessary cleanup or logging, is called a wrapper. The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and mainframe operating systems are associated with a number of terms. Shells commonly present in Unix and Unix-like systems include the Korn shell, the Bourne shell, and GNU Bash. While a Unix operating system may have a different defau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FreeBSD 10 Vi RC Firewall
FreeBSD is a free software, free-software Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version was released in 1993 developed from 386BSD, one of the first fully functional and free Unix clones on affordable home-class hardware, and has since continuously been the most commonly used BSD-derived operating system. FreeBSD maintains a complete system, delivering a kernel (operating system), kernel, device drivers, Userland (computing), userland utilities, and documentation, as opposed to Linux only delivering a Linux kernel, kernel and drivers, and relying on third-parties such as GNU for system software. The FreeBSD source code is generally released under a permissive software license, permissive FreeBSD License, BSD license, as opposed to the copyleft GPL used by Linux. The project includes a computer security, security team overseeing all software shipped in the base distribution. Third-party application software, applications may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programming Language Syntax
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 statements or 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 computer languages are based on sequences of 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 strings, before trying to figure out the general rules from these examples. Syntax therefore refers to the ''form'' of the code, and is contrasted with semantics – the ''meaning''. In processin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grep
grep is a command-line utility for searching plaintext datasets for lines that match a regular expression. Its name comes from the ed command g/re/p (global regular expression search and print), which has the same effect. grep was originally developed for the Unix operating system, but later became available for all Unix-like systems and some others such as OS-9. History Before it was named, grep was a private utility written by Ken Thompson to search files for certain patterns. Doug McIlroy, unaware of its existence, asked Thompson to write such a program. Responding that he would think about such a utility overnight, Thompson actually corrected bugs and made improvements for about an hour on his own program called "s" (short for "search"). The next day he presented the program to McIlroy, who said it was exactly what he wanted. Thompson's account may explain the belief that grep was written overnight. Thompson wrote the first version in PDP-11 assembly language to help Le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALGOL
ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the Association for Computing Machinery (ACM) in textbooks and academic sources for more than thirty years. In the sense that the syntax of most modern languages is "Algol-like", it was arguably more influential than three other high-level programming languages among which it was roughly contemporary: FORTRAN, Lisp, and COBOL. It was designed to avoid some of the perceived problems with FORTRAN and eventually gave rise to many other programming languages, including PL/I, Simula, BCPL, B, Pascal, Ada, and C. ALGOL introduced code blocks and the begin...end pairs for delimiting them. It was also the first language implementing nested function definitions with lexical scope. Moreover, it was the first programming language which gave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wish (shell)
Tk is a cross-platform widget toolkit that provides a library of basic elements of GUI widgets for building a graphical user interface (GUI) in many programming languages. It is free and open-source software released under a BSD-style software license. Tk provides many widgets commonly needed to develop desktop applications, such as button, menu, canvas, text, frame, label, etc. Tk has been ported to run on most flavors of Linux, macOS, Unix, and Microsoft Windows. Like Tcl, Tk supports Unicode within the Basic Multilingual Plane, but it has not yet been extended to handle the current extended full Unicode (e.g., UTF-16 from UCS-2 that Tk supports). Tk was designed to be extended, and a wide range of extensions are available that offer new widgets or other capabilities. Since Tcl/Tk 8, it offers "native look and feel" (for instance, menus and buttons are displayed in the manner of "native" software for any given platform). Highlights of version 8.5 include a new theming engine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bash (Unix Shell)
In computing, Bash (short for "''Bourne Again SHell''") is an interactive command interpreter and command programming language developed for UNIX-like operating systems. Created in 1989 by Brian Fox for the GNU Project, it is supported by the Free Software Foundation and designed as a 100% free alternative for the Bourne shell (sh) and other proprietary Unix shells. Since its inception, Bash has gained widespread adoption and is commonly used as the default login shell for numerous Linux distributions. It holds historical significance as one of the earliest programs ported to Linux by Linus Torvalds, alongside the GNU Compiler ( GCC). It is available on nearly all modern operating systems, making it a versatile tool in various computing environments. As a command-line interface (CLI), Bash operates within a terminal emulator, or text window, where users input commands to execute various tasks. It also supports the execution of commands from files, known as shell scripts, f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C Shell
The C shell (csh or the improved version, tcsh) is a Unix shell created by Bill Joy while he was a graduate student at University of California, Berkeley in the late 1970s. It has been widely distributed, beginning with the 2BSD release of the Berkeley Software Distribution (BSD) which Joy first distributed in 1978. Other early contributors to the ideas or the code were Michael Ubell, Eric Allman, Mike O'Brien and Jim Kulp. The C shell is a command processor which is typically run in a text window, allowing the user to type and execute commands. The C shell can also read commands from a file, called a script. Like all Unix shells, it supports filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing and iteration. What differentiated the C shell from others, especially in the 1980s, were its interactive features and overall style. Its new features made it easier and faster to use. The overall style of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KornShell
KornShell (ksh) is a Unix shell which was developed by David Korn (computer scientist), David Korn at Bell Labs in the early 1980s and announced at USENIX Annual Technical Conference, USENIX on July 14, 1983. The initial development was based on Bourne shell source code. Other early contributors were Bell Labs developers Mike Veach and Pat Sullivan, who wrote the Emacs and Vi (text editor), vi-style line editing modes' code, respectively. KornShell is backward-compatible with the Bourne shell and includes many features of the C shell, inspired by the requests of Bell Labs users. Features KornShell complies with POSIX#POSIX.2, POSIX.2, Shell and Utilities, Command Interpreter (IEEE Std 1003.2-1992.) Major differences between KornShell and the traditional Bourne shell include: * Job control (Unix), job control, alias (command), command aliasing, and command history designed after the corresponding C shell features; job control was added to the Bourne Shell in 1989 * a choice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perl
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions. Perl originally was not capitalized and the name was changed to being capitalized by the time Perl 4 was released. The latest release is Perl 5, first released in 1994. From 2000 to October 2019 a sixth version of Perl was in development; the sixth version's name was changed to Raku. Both languages continue to be developed independently by different development teams which liberally borrow ideas from each other. Perl borrows features from other programming languages including C, sh, AWK, and sed. It provides text processing facilities without the arbitrary data-length limits of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subroutine
In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide a powerful programming tool. The primary purpose is to allow for the decomposition of a large and/or complicated problem into chunks that have relatively low cognitive load and to assign the chunks meaningful names (unless they are anonymous). Judicious application can reduce the cost of developing and maintaining software, while increasing its quality and reliability. Callable units are present at multiple levels of abstraction in the programming environment. For example, a programmer may write a function in source code that is compiled to machine code that implements similar semantics. There is a callable unit in the source code and an associated one in the machine code, but they are different kinds of callable units with different impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
