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A format specifier starts with a % character and has one or more following characters that specify how to serialize a value. The format string syntax and semantics is the same for all of the functions in the printf-like family. Mismatch between the format specifiers and count and type of values can cause a crash or vulnerability.
The <inttypes.h> header (cinttypes in C++) provides features that enhance the functionality of the types defined in the <stdint.h> header. It defines macros for printf format string and scanf format string specifiers corresponding to the types defined in <stdint.h> and several functions for working with the intmax_t and uintmax_t types.
The formatting placeholders in scanf are more or less the same as that in printf, its reverse function.As in printf, the POSIX extension n$ is defined. [2]There are rarely constants (i.e., characters that are not formatting placeholders) in a format string, mainly because a program is usually not designed to read known data, although scanf does accept these if explicitly specified.
Use of a printf or scanf-like format string with embedded specifiers that indicate argument types. A sentinel value at the end of the variadic arguments. A count argument indicating the number of variadic arguments.
It accepts a string parameter called the format string, which specifies a method for rendering an arbitrary number of varied data type parameter(s) into a string. [1] The string is then printed to the kernel log. [1] It provides a printf-like abstraction and its parsing of the format string and arguments behave similarly to printf. [1]
The \n escape sequence allows for shorter code by specifying the newline in the string literal, and for faster runtime by eliminating the text formatting operation. Also, the compiler can map the escape sequence to a character encoding system other than ASCII and thus make the code more portable.
The first version interprets buffer as a format string, and parses any formatting instructions it may contain. The second version simply prints a string to the screen, as the programmer intended. Both versions behave identically in the absence of format specifiers in the string, which makes it easy for the mistake to go unnoticed by the developer.
Characters in the format string are copied to the output verbatim except when a format specifier is found which causes a value to be output. In addition to the standard format specifiers, %b causes the command to expand backslash escape sequences (for example \n for newline), and %q outputs an item that can be used as shell input. [3]