fprintf

StandardCLibrary

int fprintf( FILE *fp, char *fmt, ... )

FILE *fp; /* output stream pointer */

char *fmt; /* format string */

Synopsis

#include "stdio.h"

The fprintf function writes text to the file associated with fp according to format string fmt . Arguments following fmt are formatted and printed in the output string.

Parameters

fp is a stream pointer, open for output. fmt is a null-terminated string, containing format conversion specifications. In the processing of fmt , when fprintf encounters a conversion specification, it retrieves an argument and formats it into the output string at that location, replacing the conversion specifier. All other characters are copied into the output string.

Conversion specifiers are introduced in the format string by the percent character '%' . More specifically, conversion specifiers take the following form:

%[flags][minimum field width][precision][size specification][conversion]

where:

flags	zero or more flag characters (-, +, 0, #, or space), (see below)
minimum field width	optional, a decimal constant, or *
precision	optional, a period optionally followed by a decimal constant
size specification	optional, one of l, L or h
conversion	one of c, d, e, E, f, g, G, i, n, o, p, s, u, x, X or % (see below)

Flags:

Flag	Meaning
-	left justify the value within field width
+	Always produce a sign, either + or -
0	Use 0 for pad character, not space
#	Use a variant conversion
space	Always produce either the sign - or a space

Conversion specifiers:

Char	Data type	Meaning
c	int	character conversion
d	int	signed decimal conversion
e	double	signed decimal floating point conversion
E	double	signed decimal floating point conversion
f	double	signed decimal floating point conversion
g	double	signed decimal floating point conversion
G	double	signed decimal floating point conversion
i	int	signed decimal conversion
n	int *	writes the number of characters output so far into an integer pointer
o	int	unsigned octal conversion
p	void *	pointer conversion
s	char *	string conversion
u	int	unsigned decimal conversion
x	int	unsigned hexadecimal conversion
X	int	unsigned hexadecimal conversion
z	SS_XYZ *	floating point conversion of a 3D point
%	none	a single percent sign is output

Return Value

fprintf returns the number of characters printed.

Comments

The types of arguments must match those expected by the format specifiers in fmt, and the number of arguments must be greater than or equal to the number of specifiers in fmt; otherwise, the result of fprintf is undefined.