The function to register a new output conversion is
register_printf_function
, declared in `printf.h'.
'Y'
, it defines the conversion `%Y'.
You can redefine the built-in conversions like `%s', but flag
characters like `#' and type modifiers like `l' can never be
used as conversions; calling register_printf_function
for those
characters has no effect. It is advisable not to use lowercase letters,
since the ISO C standard warns that additional lowercase letters may be
standardized in future editions of the standard.
The handler-function is the function called by printf
and
friends when this conversion appears in a template string.
See section Defining the Output Handler, for information about how to define
a function to pass as this argument. If you specify a null pointer, any
existing handler function for spec is removed.
The arginfo-function is the function called by
parse_printf_format
when this conversion appears in a
template string. See section Parsing a Template String, for information
about this.
Attention: In the GNU C library versions before 2.0 the
arginfo-function function did not need to be installed unless
the user used the parse_printf_format
function. This has changed.
Now a call to any of the printf
functions will call this
function when this format specifier appears in the format string.
The return value is 0
on success, and -1
on failure
(which occurs if spec is out of range).
You can redefine the standard output conversions, but this is probably not a good idea because of the potential for confusion. Library routines written by other people could break if you do this.
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