C Programming: Visual Quickstart Guide

Writing to Files

Once you've opened a file for writing (meaning that you used either the w or a mode, or a variant thereof), you can write data to it. To do so, you can use the fprintf() function, which works like printf() except that it takes a file pointer as its first argument:

fprintf (file_pointer, formatting,
					extra_arguments);

The formatting signifiers are exactly the same as those used with printf() and scanf() (Table 12.2). So, to write an unsigned integer to a file, you would code

fprintf (fp, "%u", 30);

Table 12.2. The different signifiers used with printf(), sprintf(), and fprintf().

fprintf() Signifiers
Signifier	Meaning
d	integer
f	floating point number
hd	short integer
ld	long integer
hu	unsigned short integer
u	unsigned integer
lu	unsigned ...