int f_printf (
  FIL* fp,          /* [IN] File object */
  const TCHAR* fmt, /* [IN] Format stirng */
  ...
);

Description

The format control directive is a sub-set of standard library shown as follows:

    %[flag][width][precision][size]type

flag

Padding option. A - specifies left-aligned. A 0 specifies zero padded. The default setting is in right-aligned and space padded.

width

Minimum width of the field, 1-99 or *. If the width of generated string is less than the minimum width, rest field is padded with spaces or zeros. An * specifies the value comes from an argument in int type. The default setting is zero.

precision

Specifies number of fractional digits or maximum width of string, .0-.99 or .*. If the number is omitted, it is same as .0. Default setting is 6 for number and no limit for string.

size

Specifies size of integer argument, l(long) and ll(long long). If sizeof (long) == sizeof (int) is true (this is typical of 32-bit systems), prefix l can be omitted for long integer argument. The default size is int for integer argument and floating point argument is always assumed double as the default argument promotion.

type

Specifies type of the output format and the argument as shown below. The length of generated string is in assumtion of int is 32-bit.

Type	Format	Argument	Length
c	Character	int, long, long long	1 character.
d	Signed decimal		1 to 11 (20 for ll) characters.
u	Unsigned decimal		1 to 10 (20 for ll) characters.
o	Unsigned octal		1 to 11 (22 for ll) characters.
x X	Unsigned hexdecimal		1 to 8 (16 for ll) characters.
b	Unsigned binary		1 to 32 characters. Limited to lower 32 digits when ll is specified.
s	String	TCHAR*	As input string. Null pointer generates a null string.
f	Floating point (decimal)	double	1 to 31 characters. If the number of characters exceeds 31, it writes "±OV". Not a number and infinite write "NaN" and "±INF".
e E	Floating point (e notation)		4 to 31 characters. If the number of characters exceeds 31 or exponent exceeds +99, it writes "±OV".

When FatFs is configured for Unicode API (FF_LFN_UNICODE >= 1), character encoding on the string fuctions, f_putc, f_puts, f_printf and f_gets function, is also switched to Unicode. The Unicode characters in multiple encoding unit, such as surrogate pair and multi-byte sequence, should not be divided into two function calls, or the character will be lost. The character encoding on the file to be written via this function is selected by FF_STRF_ENCODE. The characters with wrong encoding or invalid for the output encoding will be lost.

If sprintf is used in the project and code conversion is not needed, f_write with sprintf will be efficient in code size and performance rather than f_printf.

    f_printf(fp, "%d", 1234);             /* "1234" */
    f_printf(fp, "%6d,%3d%%", -200, 5);   /* "  -200,  5%" */
    f_printf(fp, "%-6u", 100);            /* "100   " */
    f_printf(fp, "%ld", 12345678);        /* "12345678" */
    f_printf(fp, "%llu", 0x100000000);    /* "4294967296"   (FF_PRINT_LLI) */
    f_printf(fp, "%lld", -1LL);           /* "-1"           (FF_PRINT_LLI) */
    f_printf(fp, "%04x", 0xA3);           /* "00a3" */
    f_printf(fp, "%08lX", 0x123ABC);      /* "00123ABC" */
    f_printf(fp, "%016b", 0x550F);        /* "0101010100001111" */
    f_printf(fp, "%*d", 6, 100);          /* "   100" */
    f_printf(fp, "%s", "abcdefg");        /* "abcdefg" */
    f_printf(fp, "%5s", "abc");           /* "  abc" */
    f_printf(fp, "%-5s", "abc");          /* "abc  " */
    f_printf(fp, "%.5s", "abcdefg");      /* "abcde" */
    f_printf(fp, "%-5.2s", "abcdefg");    /* "ab   " */
    f_printf(fp, "%c", 'a');              /* "a" */
    f_printf(fp, "%12f", 10.0);           /* "   10.000000" (FF_PRINT_FLOAT) */
    f_printf(fp, "%.4E", 123.45678);      /* "1.2346E+02"   (FF_PRINT_FLOAT) */