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31 .Nd sanitizes user-supplied
32 .Xr printf 3 Ns -style
39 .Fn fmtcheck "const char *fmt_suspect" "const char *fmt_default"
49 will consume the same argument types as
53 is a valid format string.
57 family of functions cannot verify the types of arguments that they are
61 it is useful or necessary to use a user-supplied format string with no
62 guarantee that the format string matches the specified arguments.
66 was designed to be used in these cases, as in:
67 .Bd -literal -offset indent
68 printf(fmtcheck(user_format, standard_format), arg1, arg2);
71 In the check, field widths, fillers, precisions, etc.\& are ignored (unless
72 the field width or precision is an asterisk
74 instead of a digit string).
75 Also, any text other than the format specifiers
76 is completely ignored.
80 is a valid format and consumes the same argument types as
86 Otherwise, it will return
93 function does not recognize positional parameters.
94 .Sh SECURITY CONSIDERATIONS
95 Note that the formats may be quite different as long as they accept the
98 .Qq Li "%p %o %30s %#llx %-10.*e %n"
100 .Qq Li "This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n)" .
106 the first requires an integer and the second requires a long.