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Glibc
The GNU C Library, commonly known as glibc, is the GNU Project's implementation of the C standard library. Despite its name, it now also directly supports C++ (and, indirectly, other programming languages). It was started in the 1980s by the Free Software Foundation (FSF) for the GNU operating system. Released under the GNU Lesser General Public License, glibc is free software. The GNU C Library project provides the core libraries for the GNU system, as well as many systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread_create, crypt, login, exit and more. History The glibc project was initially written mostly by Roland McGrath, working for the Free Software Foundation (FSF) in the 1980s as a teenager. In February 1988, FSF described glibc as having nearly completed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malloc
C dynamic memory allocation refers to performing manual memory management for dynamic memory allocation in the C programming language via a group of functions in the C standard library, namely , , , and . The C++ programming language includes these functions; however, the operators and provide similar functionality and are recommended by that language's authors. Still, there are several situations in which using new/delete is not applicable, such as garbage collection code or performance-sensitive code, and a combination of malloc and placement new may be required instead of the higher-level new operator. Many different implementations of the actual memory allocation mechanism, used by , are available. Their performance varies in both execution time and required memory. Rationale The C programming language manages memory statically, automatically, or dynamically. Static-duration variables are allocated in main memory, usually along with the executable code of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crypt (C)
crypt is a POSIX C library function. It is typically used to compute the hash of user account passwords. The function outputs a text string which also encodes the salt (usually the first two characters are the salt itself and the rest is the hashed result), and identifies the hash algorithm used (defaulting to the "traditional" one explained below). This output string forms a password record, which is usually stored in a text file. More formally, crypt provides cryptographic key derivation functions for password validation and storage on Unix systems. Relationship to Unix crypt utility There is an unrelated crypt utility in Unix, which is often confused with the C library function. To distinguish between the two, writers often refer to the utility program as ''crypt(1)'', because it is documented in section 1 of the Unix manual pages, and refer to the C library function as ''crypt(3)'', because its documentation is in manual section 3. Details This same ''crypt'' functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C Standard Library
The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. ISO/ IEC (2018). '' ISO/IEC 9899:2018(E): Programming Languages - C ยง7'' Starting from the original ANSI C standard, it was developed at the same time as the C library POSIX specification, which is a superset of it. Since ANSI C was adopted by the International Organization for Standardization, the C standard library is also called the ISO C library. The C standard library provides macros, type definitions and functions for tasks such as string handling, mathematical computations, input/output processing, memory management, and several other operating system services. Application programming interface Header files The application programming interface (API) of the C standard library is declared in a number of header files. Each header file contains one or more function declarations, data type definitions, and macros. After a long period of stabi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux API
The Linux kernel provides several interfaces to user-space applications that are used for different purposes and that have different properties by design. There are two types of application programming interface (API) in the Linux kernel that are not to be confused: the "kernel–user space" API and the "kernel internal" API. Linux API The Linux API is the kernel–user space API, which allows programs in user space to access system resources and services of the Linux kernel. It is composed out of the System Call Interface of the Linux kernel and the subroutines in the GNU C Library (glibc). The focus of the development of the Linux API has been to provide the ''usable features'' of the specifications defined in POSIX in a way which is reasonably compatible, robust and performant, and to provide additional useful features not defined in POSIX, just as the kernel–user space APIs of other systems implementing the POSIX API also provide additional features not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Getaddrinfo
In C programming, the functions ''getaddrinfo()'' and ''getnameinfo()'' convert domain names, hostnames, and IP addresses between human-readable text representations and structured binary formats for the operating system's networking API. Both functions are contained in the POSIX standard application programming interface (API). getaddrinfo and getnameinfo are inverse functions of each other. They are network protocol agnostic, and support both IPv4 and IPv6. It is the recommended interface for name resolution in building protocol independent applications and for transitioning legacy IPv4 code to the IPv6 Internet. Internally, the functions perform resolutions using the Domain Name System (DNS) by calling other, lower level functions, such as gethostbyname(). On February 16 2016 a security bug was announced in the glibc implementation of getaddrinfo(), using a buffer overflow technique, that may allow execution of arbitrary code by the attacker. struct addrinfo The C data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel System Call Interface And Glibc
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name "GNU/Linux" to emphasize the importance of GNU software, causing some controversy. Popular Linux distributions include Debian, Fedora Linux, and Ubuntu, the latter of which itself consists of many different distributions and modifications, including Lubuntu and Xubuntu. Commercial distributions include Red Hat Enterprise Linux and SUSE Linux Enterprise. Desktop Linux distributions include a windowing system such as X11 or Wayland, and a desktop environment such as GNOME or KDE Plasma. Distributions intended for servers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Printf
The printf format string is a control parameter used by a class of functions in the input/output libraries of C and many other programming languages. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "''print f''ormatted". printf format strings are complementary to scanf format strings, which provide formatted input ( lexing aka. parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or lexers/parsers, but are sufficient for many purposes. Many languages other than C copy the printf format string syntax closely or exactly in their own I/O functions. Mismatches between the format specifiers and typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write (system Call)
The write is one of the most basic routines provided by a Unix-like operating system kernel. It writes data from a buffer declared by the user to a given device, such as a file. This is the primary way to output data from a program by directly using a system call. The destination is identified by a numeric code. The data to be written, for instance a piece of text, is defined by a pointer and a size, given in number of bytes. write thus takes three arguments: # The file code (file descriptor or fd). # The pointer to a buffer where the data is stored (buf). # The number of bytes to write from the buffer (nbytes). POSIX usage The write call interface is standardized by the POSIX specification. Data is written to a file by calling the write function. The function prototype is: ssize_t write(int fd, const void *buf, size_t nbytes); In above syntax, ssize_t is a typedef. It is a signed data type defined in stddef.h. Note that write() does not return an unsigned value; it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dlopen
Dynamic loading is a mechanism by which a computer program can, at run time, load a library (or other binary) into memory, retrieve the addresses of functions and variables contained in the library, execute those functions or access those variables, and unload the library from memory. It is one of the 3 mechanisms by which a computer program can use some other software; the other two are static linking and dynamic linking. Unlike static linking and dynamic linking, dynamic loading allows a computer program to start up in the absence of these libraries, to discover available libraries, and to potentially gain additional functionality. History Dynamic loading was a common technique for IBM's operating systems for System/360 such as OS/360, particularly for I/O subroutines, and for COBOL and PL/I runtime libraries, and continues to be used in IBM's operating systems for z/Architecture, such as z/OS. As far as the application programmer is concerned, the loading is largely tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pthread Create
POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. Each flow of work is referred to as a ''thread'', and creation and control over these flows is achieved by making calls to the POSIX Threads API. POSIX Threads is an API defined by the standard ''POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995)''. Implementations of the API are available on many Unix-like POSIX-conformant operating systems such as FreeBSD, NetBSD, OpenBSD, Linux, macOS, Android, Solaris, Redox, and AUTOSAR Adaptive, typically bundled as a library libpthread. DR-DOS and Microsoft Windows implementations also exist: within the SFU/SUA subsystem which provides a native implementation of a number of POSIX APIs, and also within third-party packages such as ''pthreads-w32'', which implements pthreads on top of existing Windows AP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Project
The GNU Project () is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and Computer hardware, computing devices by collaboratively developing and publishing software that gives everyone the rights to freely run the software, copy and distribute it, study it, and modify it. GNU software grants these rights in its GNU General Public License, license. In order to ensure that the ''entire'' software of a computer grants its users all freedom rights (use, share, study, modify), even the most fundamental and important part, the operating system (including all its numerous utility programs) needed to be free software. According to its manifesto, the founding goal of the project was to build a free operating system, and if possible, "everything useful that normally comes with a Unix system so that one could get along without any software that is not fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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