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33 .Nd sanitizes user-supplied
34 .Xr printf 3 Ns -style
41 .Fn fmtcheck "const char *fmt_suspect" "const char *fmt_default"
51 will consume the same argument types as
55 is a valid format string.
59 family of functions cannot verify the types of arguments that they are
63 it is useful or necessary to use a user-supplied format string with no
64 guarantee that the format string matches the specified arguments.
68 was designed to be used in these cases, as in:
69 .Bd -literal -offset indent
70 printf(fmtcheck(user_format, standard_format), arg1, arg2);
73 In the check, field widths, fillers, precisions, etc.\& are ignored (unless
74 the field width or precision is an asterisk
76 instead of a digit string).
77 Also, any text other than the format specifiers
78 is completely ignored.
82 is a valid format and consumes the same argument types as
88 Otherwise, it will return
95 function does not recognize positional parameters.
96 .Sh SECURITY CONSIDERATIONS
97 Note that the formats may be quite different as long as they accept the
100 .Qq Li "%p %o %30s %#llx %-10.*e %n"
102 .Qq Li "This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n)" .
108 the first requires an integer and the second requires a long.