|FMTCHECK(3)||Library Functions Manual||FMTCHECK(3)|
sanitizes user-supplied printf(3)-style
const char *
char *fmt_suspect, const
scans fmt_suspect and
fmt_default to determine if
fmt_suspect will consume the same argument types as
fmt_default and to ensure that
fmt_suspect is a valid format string.
The printf(3) family of functions cannot verify the types of arguments that they are passed at run-time. In some cases, like catgets(3), it is useful or necessary to use a user-supplied format string with no guarantee that the format string matches the specified arguments.
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.
If fmt_suspect is a valid format and
consumes the same argument types as fmt_default, then
fmtcheck() will return
fmt_suspect. Otherwise, it will return
Note that the formats may be quite different as long as they
accept the same arguments. For example, "
%p %o %30s
%#llx %-10.*e %n" is compatible with "
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.
fmtcheck() function does not
understand all of the conversions that printf(3) does.
|October 16, 2002||Debian|