| | 1 | .\" Copyright (c) 2000 The NetBSD Foundation, Inc. |
| | 2 | .\" All rights reserved. |
| | 3 | .\" |
| | 4 | .\" This file was contributed to The NetBSD Foundation by Allen Briggs. |
| | 5 | .\" |
| | 6 | .\" Redistribution and use in source and binary forms, with or without |
| | 7 | .\" modification, are permitted provided that the following conditions |
| | 8 | .\" are met: |
| | 9 | .\" 1. Redistributions of source code must retain the above copyright |
| | 10 | .\" notice, this list of conditions and the following disclaimer. |
| | 11 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| | 12 | .\" notice, this list of conditions and the following disclaimer in the |
| | 13 | .\" documentation and/or other materials provided with the distribution. |
| | 14 | .\" 3. All advertising materials mentioning features or use of this software |
| | 15 | .\" must display the following acknowledgement: |
| | 16 | .\" This product includes software developed by the NetBSD |
| | 17 | .\" Foundation, Inc. and its contributors. |
| | 18 | .\" 4. Neither the name of The NetBSD Foundation nor the names of its |
| | 19 | .\" contributors may be used to endorse or promote products derived |
| | 20 | .\" from this software without specific prior written permission. |
| | 21 | .\" |
| | 22 | .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| | 23 | .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| | 24 | .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| | 25 | .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| | 26 | .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| | 27 | .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| | 28 | .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| | 29 | .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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| | 32 | .\" POSSIBILITY OF SUCH DAMAGE. |
| | 33 | .\" |
| | 34 | .\" $FreeBSD: src/lib/libc/gen/fmtcheck.3,v 1.4 2001/10/01 16:08:50 ru Exp $ |
| | 35 | .Dd October 17, 2000 |
| | 36 | .Os |
| | 37 | .Dt FMTCHECK 3 |
| | 38 | .Sh NAME |
| | 39 | .Nm fmtcheck |
| | 40 | .Nd sanitizes user-supplied |
| | 41 | .Xr printf 3 Ns -style |
| | 42 | format string |
| | 43 | .Sh LIBRARY |
| | 44 | .Lb libc |
| | 45 | .Sh SYNOPSIS |
| | 46 | .In stdio.h |
| | 47 | .Ft const char * |
| | 48 | .Fn fmtcheck "const char *fmt_suspect" "const char *fmt_default" |
| | 49 | .Sh DESCRIPTION |
| | 50 | The |
| | 51 | .Fn fmtcheck |
| | 52 | scans |
| | 53 | .Fa fmt_suspect |
| | 54 | and |
| | 55 | .Fa fmt_default |
| | 56 | to determine if |
| | 57 | .Fa fmt_suspect |
| | 58 | will consume the same argument types as |
| | 59 | .Fa fmt_default |
| | 60 | and to ensure that |
| | 61 | .Fa fmt_suspect |
| | 62 | is a valid format string. |
| | 63 | .Pp |
| | 64 | The |
| | 65 | .Xr printf 3 |
| | 66 | family of functions can not verify the types of arguments that they are |
| | 67 | passed at run-time. In some cases, like |
| | 68 | .Xr catgets 3 , |
| | 69 | it is useful or necessary to use a user-supplied format string with no |
| | 70 | guarantee that the format string matches the specified parameters. |
| | 71 | .Pp |
| | 72 | The |
| | 73 | .Fn fmtcheck |
| | 74 | was designed to be used in these cases, as in: |
| | 75 | .Bd -literal -offset indent |
| | 76 | printf(fmtcheck(user_format, standard_format), arg1, arg2); |
| | 77 | .Ed |
| | 78 | .Pp |
| | 79 | In the check, field widths, fillers, precisions, etc. are ignored (unless |
| | 80 | the field width or precision is an asterisk |
| | 81 | .Ql * |
| | 82 | instead of a digit string). Also, any text other than the format specifiers |
| | 83 | is completely ignored. |
| | 84 | .Pp |
| | 85 | Note that the formats may be quite different as long as they accept the |
| | 86 | same parameters. For example, |
| | 87 | .Qq Li "%p %o %30s %#llx %-10.*e %n" |
| | 88 | is compatible with |
| | 89 | .Qq Li "This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n)" . |
| | 90 | However, |
| | 91 | .Qq Li %o |
| | 92 | is not equivalent to |
| | 93 | .Qq Li %lx |
| | 94 | because |
| | 95 | the first requires an integer and the second requires a long. |
| | 96 | .Sh RETURN VALUES |
| | 97 | If |
| | 98 | .Fa fmt_suspect |
| | 99 | is a valid format and consumes the same argument types as |
| | 100 | .Fa fmt_default , |
| | 101 | then the |
| | 102 | .Fn fmtcheck |
| | 103 | will return |
| | 104 | .Fa fmt_suspect . |
| | 105 | Otherwise, it will return |
| | 106 | .Fa fmt_default . |
| | 107 | .Sh SEE ALSO |
| | 108 | .Xr printf 3 |
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