Printf

printf is a C standard libraryfunction and is also a Linux terminal (shell) command that formatstext and writes it to standard output. The function accepts a format C-stringargument and a variable number of value arguments that the function serializes per the format string. Mismatch between the format specifiers and count and type of values results in undefined behavior, and the program might crash or vulnerabilities may arise.

The format string is encoded as a template language consisting of verbatim text and format specifiers that each specify how to serialize a value. As the format string is processed left-to-right, a subsequent value is used for each format specifier found. A format specifier starts with a % character and has one or more following characters that specify how to serialize a value.

The standard library provides other, similar functions that form a family of printf-like functions. The functions share the same formatting capabilities but provide different behavior such as output to a different destination or safety measures that limit exposure to vulnerabilities. Functions of the printf-family have been implemented in other computer programming contexts (i.e., programming languages) with the same or similar syntax and semantics.

The scanf() C standard library function complements printf by providing formatted input (a.k.a. lexing, a.k.a. parsing) via a similar format string syntax.

The name, printf, is short for print formatted where print refers to output to a printer although the function is not limited to printer output. Today, print refers to output to any text-based environment such as a terminal or a file.