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vprintf() -- STDIO Function (libc) Print formatted text into standard output stream #include <stdarg.h> #include <stdio.h> int vprintf(format, arguments) char *format; va_list arguments; vprintf() constructs a formatted string and writes it into the standard output stream. It translates integers, floating-point numbers, and strings into a variety of text formats. vprintf can handle a variable list of arguments of various types. It is roughly equivalent to printf()'s conversion specifier %r. format points to a string that can contain text, character constants, and one or more conversion specifications. A conversion specification defines how a particular data type is converted into a particular text format. Each conversion specification is introduced with the percent sign `%'. (To print a literal percent sign, use the escape sequence `%%'.) See printf() for further discussion of the conversion specification and for a table of the type specifiers that can be used with vprintf(). After format comes arguments. This is of type va_list, which is defined in the header stdarg.h. It has been initialized by the macro va_start() and points to the base of the list of arguments used by vprintf(). Each argument must have basic type that can be converted to a pointer simply by adding an `*' after the type name. This is the same restriction that applies to the arguments to the macro va_arg(). For more information, see va_arg(). arguments should access one argument for each conversion specification in format of the type appropriate to conversion specification. For example, if format contains conversion specifications for an int, a long, and a string, then arguments access three arguments, being, respectively, an int, a long, and a char *. If there are fewer arguments than conversion specifications, then vprintf's behavior is undefined (and probably unwelcome). If there are more, then vprintf() evaluates and then ignores every argument without a corresponding conversion specification. If an argument is not of the same type as its corresponding type specification, then the behavior of vprintf() is undefined; thus, accessing an int where vprintf() expects a char * may generate unwelcome results. If it writes the formatted string correctly, vprintf() returns the number of characters written; otherwise, it returns a negative number. See Also fprintf(), libc, printf(), sprintf(), vfprintf(), vsprintf() ANSI Standard, §7.9.6.8 Notes vprintf() can construct a string up to at least 509 characters long.