You copied the Doc URL to your clipboard.
_sys_flen()
Defined in rt_sys.h, the _sys_flen() function returns the current length of a file.
Syntax
long_sys_flen(FILEHANDLEfh);
Usage
This function is used by _sys_seek() to
convert an offset relative to the end of a file into an offset relative
to the beginning of the file.
You do not have to define _sys_flen() if
you do not intend to use fseek().
If you retarget at system _sys_level,
you must supply *() _sys_flen(), even if the underlying system
directly supports seeking relative to the end of a file.
Returns
This function returns the current length of the file fh,
or a negative error indicator.