Manpages - fmtcheck.3bsd

(See

for include usage.)

The

function scans

and

to determine if

will consume the same argument types as

and to ensure that

is a valid format string.

The

family of functions can not verify the types of arguments that they are passed at run-time. In some cases, like

it is useful or necessary to use a user-supplied format string with no guarantee that the format string matches the specified parameters.

The

function was designed to be used in these cases, as in:

printf(fmtcheck(user_format, standard_format), arg1, arg2);

In the check, field widths, fillers, precisions, etc. are ignored (unless the field width or precision is an asterisk

instead of a digit string). Also, any text other than the format specifiers is completely ignored.

Note that the formats may be quite different as long as they accept the same parameters. For example, “%ld %o %30s %#llx %-10.*e %n” is compatible with “This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n).” However, “%o” is not equivalent to “%lx” because the first requires an integer and the second requires a long, and “%p” is not equivalent to “%lu” because the first requires a pointer and the second requires a long.

is a valid format and consumes the same argument types as

then the

function will return

Otherwise, it will return