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The printf format string is complementary to the scanf format string, which provides formatted input (lexing a.k.a. parsing). Both format strings provide relatively simple functionality compared to other template engines, lexers and parsers. The formatting design has been copied in other programming languages.
In Unix and Unix-like operating systems, printf is a shell builtin (and utility program [2]) that formats and outputs text like the same-named C function. Originally named for outputting to a printer, it actually outputs to standard output. [3] The command accepts a format string, which specifies how to format values, and a list of values.
printf(string format, items-to-format) It can take one or more arguments, where the first argument is a string to be written. This string can contain special formatting codes which are replaced by items from the remainder of the arguments. For example, an integer can be printed using the "%d" formatting code, e.g.: printf("%d", 42);
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. Format bugs arise because C's argument passing conventions are not type-safe.
String interpolation is an alternative to building string via concatenation, which requires repeat quoting and unquoting; [2] or substituting into a printf format string, where the variable is far from where it is used. Compare:
printf() family of routines, for spoiling the execution stack when the format string does not match the arguments given. This fundamental flaw created an entire class of attacks: format string attacks; gets() and scanf() family of I/O routines, for lack of (either any or easy) input length checking.
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. This header was added in C99.
format(archetype, string-index, first-to-check) The format attribute specifies that a function takes printf, scanf, strftime or strfmon style arguments which should be type-checked against a format string. For example, the declaration: