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The C programming language provides many standard library functions for file input and output.These functions make up the bulk of the C standard library header <stdio.h>. [1] The functionality descends from a "portable I/O package" written by Mike Lesk at Bell Labs in the early 1970s, [2] and officially became part of the Unix operating system in Version 7.
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).
Zero-byte files may arise in cases where a program creates a file but aborts or is interrupted prematurely while writing to it. Because writes are cached in memory and only flushed to disk at a later time ( page cache ), a program that does not flush its writes to disk or terminate normally may result in a zero-byte file.
The C language specification includes the typedef s size_t and ptrdiff_t to represent memory-related quantities. Their size is defined according to the target processor's arithmetic capabilities, not the memory capabilities, such as available address space. Both of these types are defined in the <stddef.h> header (cstddef in C++).
Write 4 bytes to shadow stack WRSSQ m64,r64: NP REX.W 0F 38 F6 /r: Write 8 bytes to shadow stack WRUSSD m32,r32: 66 0F 38 F5 /r: Write 4 bytes to user shadow stack 0 WRUSSQ m64,r64: 66 REX.W 0F 38 F5 /r: Write 8 bytes to user shadow stack SETSSBSY: F3 0F 01 E8: Mark shadow stack busy CLRSSBSY m64: F3 0F AE /6: Clear shadow stack busy flag CET_IBT
C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the type followed by the variable name.
Unix eliminated this complexity with the concept of a data stream: an ordered sequence of data bytes which can be read until the end of file. A program may also write bytes as desired and need not, and cannot easily declare their count or grouping.
dd is a command-line utility for Unix, Plan 9, Inferno, and Unix-like operating systems and beyond, the primary purpose of which is to convert and copy files. [1] On Unix, device drivers for hardware (such as hard disk drives) and special device files (such as /dev/zero and /dev/random) appear in the file system just like normal files; dd can also read and/or write from/to these files ...