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Execve
In computing, exec is a functionality of an operating system that runs an executable file in the context of an already existing process (computing), process, replacing the previous executable. This act is also referred to as an overlay. It is especially important in Unix-like systems, although it exists elsewhere. As no new process is created, the process identifier (PID) does not change, but the machine code, data (computing), data, heap (programming), heap, and run-time stack, stack of the process are replaced by those of the new program. The ''exec'' call is available for many programming languages including compiler, compilable languages and some scripting languages. In operating system shell, OS command interpreters, the shell builtin, built-in command replaces the shell process with the specified program. Nomenclature Interfaces to ''exec'' and its implementations vary. Depending on programming language it may be accessible via one or more function (programming), functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix. Linux is provided under the GNU General Public License version 2 only, but it contains files under other compatible licenses. Since the late 1990s, it has been included as part of a large number of operating system distributions, many of which are commonly also called Linux. Linux is deployed on a wide variety of computing systems, such as embedded devices, mobile devices (including its use in the Android operating system), personal computers, servers, mainframes, and supercomputers. It can be tailored for specific architectures and for several usage scenarios using a family of simple commands (that is, without the need of manually editing its source code ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PATH (variable)
PATH is an environment variable on Unix-like operating systems, DOS, OS/2, and Microsoft Windows, specifying a set of directories where executable programs are located. In general, each executing process or user session has its own PATH setting. History Multics originated the idea of a search path. The early Unix shell only looked for program names in /bin, but by Version 3 Unix the directory was too large and /usr/bin, and a search path, became part of the operating system. Unix and Unix-like On POSIX and Unix-like operating systems, the $PATH variable is specified as a list of one or more directory names separated by colon (:) characters. Directories in the PATH-string are not meant to be escaped, making it impossible to have directories with : in their name. The /bin, /usr/bin, and /usr/local/bin directories are typically included in most users' $PATH setting (although this varies from implementation to implementation). The superuser also typically has /sbin and /usr/sbin ent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Call
In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive or accessing the device's camera), creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system. In most systems, system calls can only be made from userspace processes, while in some systems, OS/360 and successors for example, privileged system code also issues system calls. Privileges The architecture of most modern processors, with the exception of some embedded systems, involves a security model. For example, the ''rings'' model specifies multiple privilege levels under which software may be executed: a program is usually limited to its own address space so that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C (programming Language)
C (''pronounced like the letter c'') is a General-purpose language, general-purpose computer programming language. It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted CPUs. It has found lasting use in operating systems, device drivers, protocol stacks, though decreasingly for application software. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems. A successor to the programming language B (programming language), B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the Unix operating system. During the 1980s, C gradually gained popularity. It has become one of the measuring programming language popularity, most widely used programming languages, with C compilers avail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null-terminated String
In computer programming, a null-terminated string is a character string stored as an array containing the characters and terminated with a null character (a character with a value of zero, called NUL in this article). Alternative names are C string, which refers to the C programming language and ASCIIZ (although C can use encodings other than ASCII). The length of a string is found by searching for the (first) NUL. This can be slow as it takes O(''n'') (linear time) with respect to the string length. It also means that a string cannot contain a NUL (there is a NUL in memory, but it is after the last character, not "in" the string). History Null-terminated strings were produced by the .ASCIZ directive of the PDP-11 assembly languages and the ASCIZ directive of the MACRO-10 macro assembly language for the PDP-10. These predate the development of the C programming language, but other forms of strings were often used. At the time C (and the languages that it was derived from) was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pointer (computer Programming)
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer ''references'' a location in memory, and obtaining the value stored at that location is known as ''dereferencing'' the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture. Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables and tree structures). In particular, it is often much cheaper in time and space to copy and dereference pointers th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interface
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and providing information to them as to what actions they are to perform. In some cases the invocation is conditional based on conditions established by the user or previous executables. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods. Today, many users rely upon graphical user interfaces and menu-driven interactions. However, some programming and maintenance tasks may not have a graphical user interface and use a command line. Alternatives to the command-line interface include text-based user interface menus (for example, IBM AIX SMIT), keyboard shortcuts, and various desktop metaphors centered on the pointer (usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environment Variable
An environment variable is a dynamic-named value that can affect the way running processes will behave on a computer. They 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 variables. By default, when a p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DOS Operating Systems
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communications network * Disk operating system ** List of disk operating systems, Apple DOS, Atari DOS, DOS/360, etc. * Distributed operating system Music Albums * ''Dos'' (Altered State album) * ''Dos'' (Dos album) * ''Dos'' (Fanny Lú album) * ''Dos'' (Gerardo album) * ''Dos'' (Malo album), 1972 * ''Dos'' (Myriam Hernández album), 1989 * ''Dos'', album by Wooden Shjips, 2009 * ''¡Dos!'', album by Green Day Other uses in music * Dos (band), an American band * DOS (concert), by Filipino singer Daniel Padilla Organisations * Democratic Opposition of Serbia, a former political alliance * Department of Space, India * Deutscher Olympischer Sportbund * Directorate of Overseas Surveys, UK 1957–1984 *Dominus Obsequious Sororium, within cult NXI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific service or product for customers *Business process modeling, activity of representing processes of an enterprise in order to deliver improvements *Manufacturing process management, a collection of technologies and methods used to define how products are to be manufactured. *Process architecture, structural design of processes, applies to fields such as computers, business processes, logistics, project management *Process costing, a cost allocation procedure of managerial accounting * Process management, ensemble of activities of planning and monitoring the performance of a business process or manufacturing processes *Process management (project management), a systematic series of activities directed towards causing an end result in engineeri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interfaces (APIs), along with command line shells and utility interfaces, for software compatibility (portability) with variants of Unix and other operating systems. POSIX is also a trademark of the IEEE. POSIX is intended to be used by both application and system developers. Name Originally, the name "POSIX" referred to IEEE Std 1003.1-1988, released in 1988. The family of POSIX standards is formally designated as IEEE 1003 and the ISO/IEC standard number is ISO/IEC 9945. The standards emerged from a project that began in 1984 building on work from related activity in the ''/usr/group'' association. Richard Stallman suggested the name ''POSIX'' (pronounced as ''pahz-icks,'' as in ''positive'', not as ''poh-six'') to the IEEE instead of former ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
