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
If there was a write error then -1 is returned and the task’s errno is
set to indicate the reason. A task
can obtain its errno value using the stdioGET_ERRNO()
The example provided on the ff_fgets() documentation
page shows how ff_fprintf() is used.
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