If any single placeholder specifies a parameter, all the rest of the placeholders MUST also specify a parameter.ДЇor example, printf('%2$d %2$#x %1$d %1$#x',16,17) produces 17 0x11 16 0x10. N is the number of the parameter to display using this format specifier, allowing the parameters provided to be output multiple times, using varying format specifiers or in different orders. The Parameter field can be omitted or can be: This is a POSIX extension and not in C99. Printf ( 'Your age is %d', age ) Syntax However, it can also be the value of a variable, which allows for dynamic formatting but also a security vulnerability known as an uncontrolled format string exploit. The format string itself is very often a string literal, which allows static analysis of the function call.

Mismatches between the format specifiers and type of the data can cause crashes and other vulnerabilities. Many languages other than C copy the printf format string syntax closely or exactly in their own I/O functions. 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. printf format strings are complementary to scanf format strings, which provide formatted input ( lexing aka.

'printf' is the name of one of the main C output functions, and stands for ' print formatted'. 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. 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.

Java string format