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[FreeRTOS+FAT Standard API Reference]
size_t ff_fprintf( FF_FILE * pxStream, const char *pcFormat, ... );
Writes formatted data to a file in exactly the same way sprintf() writes formatted data to a buffer, or printf() writes formatted data to a console.
ff_fprintf() calls vsnprintf(), which must be provided by your C library for a project that uses ff_fprintf() to link. The format specifiers and extensions (for example “%02D”, “%s”, etc.) that are available for use will depend on your C library.
FF_FPRINTF_SUPPORT must be set to 1 in FreeRTOSFATConfig.h for ff_fprintf() to be available.
Note: ff_fprintf() is quite a heavy function as it allocates memory into which it writes is formatted data before outputting the data to the file. It also uses vsnprintf(), which can result in lots of additional library code being included in your project.
A pointer to the file to which the formatted data is being written.
This is the same pointer that was returned from the call
to ff_fopen() used to originally open the file.
The format string, which is used in exactly the same
way as the format string input to a printf() call. The
format specifiers that are available for use will
depend on the C library in use.
A variable list of argument values – with one value for
each specifier included in the format string.
If ff_printf() could not allocate a buffer then 0 is returned.
If data was written to the file then number number of bytes written is returned.
The example provided on the ff_fgets() documentation page shows how ff_fprintf() is used.