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Noclobber
In computing, clobbering is the act of overwriting a resource such as a file, processor register or a region of memory, such that its content is lost. Generally, the term is used in the context of unintentional loss of information, but it can be used for intentional overwriting as well. The Jargon File defines clobbering as Examples File redirection In many shells, the > file redirection operator clobbers if the output path refers to an existing file. This can be prevented in bash and ksh via the command set -o noclobber and in csh and tcsh via set noclobber. Subsequently, attempting to clobber via redirection fails with an error message. For example: $ echo "Hello, world" >file.txt $ cat file.txt Hello, world $ echo "This will overwrite the first greeting." >file.txt $ cat file.txt This will overwrite the first greeting. $ set -o noclobber $ echo "Can we overwrite it again?" >file.txt -bash: file.txt: cannot overwrite existing file $ echo "But we can use the >, opera ... [...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] |
Computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and software. Computing has scientific, engineering, mathematical, technological, and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology, and software engineering. The term ''computing'' is also synonymous with counting and calculation, calculating. In earlier times, it was used in reference to the action performed by Mechanical computer, mechanical computing machines, and before that, to Computer (occupation), human computers. History The history of computing is longer than the history of computing hardware and includes the history of methods intended for pen and paper (or for chalk and slate) with or without the aid of tables. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tcsh
tcsh ( “tee-see-shell”, “tee-shell”, or as “tee see ess aitch”, tcsh) is a Unix shell based on and backward compatible with the C shell (csh). Shell It is essentially the C shell with programmable command-line completion, command-line editing, and a few other features. Unlike the other common shells, functions cannot be defined in a tcsh script and the user must use aliases instead (as in csh). It is the native root shell for some BSD-based systems, including FreeBSD 13 and earlier. (FreeBSD 14 changed the default root shell to sh to match the default user shell whereas OpenBSD uses the Korn shell ksh for both root and regular users.) tcsh added filename and command completion and command line editing concepts borrowed from the TENEX operating system, which is the source of the “t”. Because it only added functionality and did not change what was there, tcsh remained backward compatible with the original C shell. Though it started as a side branch from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Compiler Collection
The GNU Compiler Collection (GCC) is a collection of compilers from the GNU Project that support various programming languages, Computer architecture, hardware architectures, and operating systems. The Free Software Foundation (FSF) distributes GCC as free software under the GNU General Public License (GNU GPL). GCC is a key component of the GNU toolchain which is used for most projects related to GNU and the Linux kernel. With roughly 15 million lines of code in 2019, GCC is one of the largest free programs in existence. It has played an important role in the growth of free software, as both a tool and an example. When it was first released in 1987 by Richard Stallman, GCC 1.0 was named the GNU C Compiler since it only handled the C (programming language), C programming language. It was extended to compile C++ in December of that year. Compiler#Front end, Front ends were later developed for Objective-C, Objective-C++, Fortran, Ada (programming language), Ada, Go (programming la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Assembly Language
In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly language usually has one statement per machine instruction (1:1), but constants, comments, assembler directives, symbolic labels of, e.g., memory locations, registers, and macros are generally also supported. The first assembly code in which a language is used to represent machine code instructions is found in Kathleen and Andrew Donald Booth's 1947 work, ''Coding for A.R.C.''. Assembly code is converted into executable machine code by a utility program referred to as an '' assembler''. The term "assembler" is generally attributed to Wilkes, Wheeler and Gill in their 1951 book '' The Preparation of Programs for an Electronic Dig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environment Variable
An environment variable is a user-definable value that can affect the way running processes will behave on a computer. Environment variables are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process. They were introduced in their modern form in 1979 with Version 7 Unix, so are included in all Unix operating system flavors and variants from that point onward including Linux and macOS. From PC DOS 2.0 in 1982, all succeeding Microsoft operating systems, including Microsoft Windows, and OS/2 also have included them as a feature, although with somewhat different syntax, usage and standard variable names. Design In all Unix and Unix-like systems, as well as on Windows, each process has its own separate set of environment vari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uninstall
An uninstaller, also called a deinstaller, is a variety of utility software designed to remove other software or parts of it from a computer. It is the opposite of an installer. Uninstallers are useful primarily when software components are installed in multiple directories, or where some software components might be shared between the system being uninstalled and other systems that remain in use. Generic uninstallers became prevalent in the 1990s due to the popularity of shared libraries and the constraints of then-current operating systems, especially Microsoft Windows XP. Declining storage costs and increasing capacity subsequently made reclaiming disk space less urgent, while end-user applications have increasingly relied on simpler installation architectures that consolidate all components to facilitate removal. Components Typical uninstallers contain the following components: * Logger: The Logger is used to log installations (e.g., log which files were added or changed, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Makefile
In software development, Make is a command-line interface software tool that performs actions ordered by configured Dependence analysis, dependencies as defined in a configuration file called a ''makefile''. It is commonly used for build automation to Software build, build executable, executable code (such as a computer program, program or library (software), library) from source code. But, not limited to building, Make can perform any operation available via the Shell (computing), operating system shell. Make is widely used, especially in Unix and Unix-like operating systems, even though many competing technologies and tools are available, including similar tools that perform actions based on dependencies, some compiler (computing), compilers and interactively via an integrated development environment. In addition to referring to the original Unix tool, Make is also a technology since multiple tools have been implementation, implemented with roughly the same functionality inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Make (software)
In software development, Make is a command-line interface software tool that performs actions ordered by configured dependencies as defined in a configuration file called a ''makefile''. It is commonly used for build automation to build executable code (such as a program or library) from source code. But, not limited to building, Make can perform any operation available via the operating system shell. Make is widely used, especially in Unix and Unix-like operating systems, even though many competing technologies and tools are available, including similar tools that perform actions based on dependencies, some compilers and interactively via an integrated development environment. In addition to referring to the original Unix tool, Make is also a technology since multiple tools have been implemented with roughly the same functionality including similar makefile syntax and semantics. Origin Stuart Feldman created Make while at Bell Labs. An early version was completed in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Switch (command Line)
A command-line interface (CLI) is a means of interacting with software via 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 utilities still provide CLI. A CLI enables automating programs since commands can be stored in a script 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 include a GUI (including the desktop metaphor such as Windows), text-based menuing (including DOS S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cp (Unix)
cp is a shell command for copying files and directories. If the user has write access to a target file, the command copies the content by opening it in update mode. This preserves the file's inode instead of creating a new file with default permissions. The command was part of Version 1 Unix, and is specified by POSIX. The implementation from GNU has many additional options beyond the POSIX specification. The command is bundled in GNU Core Utilities and is available in the EFI shell. Options *-f (force) – specifies removal of each target file if it cannot be opened for write operations; removal precedes any copying * -H (dereference) – follows symbolic link In computing, a symbolic link (also symlink or soft link) is a file whose purpose is to point to a file or directory (called the "target") by specifying a path thereto. Symbolic links are supported by POSIX and by most Unix-like operating syste ...s so that the destination has the target file rather ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mv (Unix)
mv is a shell command for renaming and moving files and directories. If both items are on the same file system, the command renames; otherwise items are copied to the destination and the old items are removed (more specifically unlinked). To move between two directories, the user must have write permission for both because the command modifies the content of both. For a rename, an item's timestamp is not modified. On Unix implementations derived from AT&T Unix, cp, ln and mv are implemented as a single program with hard-linked binaries. History Multics provided a file move/rename command named . A version with the contracted name appeared in Version 1 Unix and became part of the X/Open Portability Guide issue 2 of 1987. The version in GNU Core Utilities was written by Mike Parker, David MacKenzie, and Jim Meyering. The command is available in Windows via UnxUtils. The command was ported to IBM i. Options Most implementations support: * -i interactive; the comma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
