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27 .\" $FreeBSD: /repoman/r/ncvs/src/lib/libc/gen/fmtcheck.3,v 1.9 2004/07/02 23:52:10 ru Exp $
33 .Nd sanitizes user-supplied
34 .Xr printf 3 Ns -style
37 .ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
42 .Fn fmtcheck "const char *fmt_suspect" "const char *fmt_default"
52 will consume the same argument types as
56 is a valid format string.
60 family of functions cannot verify the types of arguments that they are
64 it is useful or necessary to use a user-supplied format string with no
65 guarantee that the format string matches the specified arguments.
69 was designed to be used in these cases, as in:
70 .Bd -literal -offset indent
71 printf(fmtcheck(user_format, standard_format), arg1, arg2);
74 In the check, field widths, fillers, precisions, etc.\& are ignored (unless
75 the field width or precision is an asterisk
77 instead of a digit string).
78 Also, any text other than the format specifiers
79 is completely ignored.
83 is a valid format and consumes the same argument types as
89 Otherwise, it will return
91 .Sh SECURITY CONSIDERATIONS
92 Note that the formats may be quite different as long as they accept the
95 .Qq Li "%p %o %30s %#llx %-10.*e %n"
97 .Qq Li "This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n)" .
103 the first requires an integer and the second requires a long.
109 function does not understand all of the conversions that