man3/rpmatch.3

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  24 .\" References:
  25 .\"   glibc manual and source
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  27 .\" 2006-05-19, mtk, various edits and example program
  28 .\"
  29 .TH RPMATCH 3 2015-07-23 "GNU" "Linux Programmer's Manual"
  30 .SH NAME
  31 rpmatch \- determine if the answer to a question is affirmative or negative
  32 .SH SYNOPSIS
  33 .nf
  34 .B #include <stdlib.h>
  35
  36 .BI "int rpmatch(const char *" response );
  37 .fi
  38 .sp
  39 .in -4n
  40 Feature Test Macro Requirements for glibc (see
  41 .BR feature_test_macros (7)):
  42 .in
  43 .sp
  44 .BR rpmatch ():
  45 _SVID_SOURCE
  46 .SH DESCRIPTION
  47 .BR rpmatch ()
  48 handles a user response to yes or no questions, with
  49 support for internationalization.
  50
  51 .I response
  52 should be a null-terminated string containing a
  53 user-supplied response, perhaps obtained with
  54 .BR fgets (3)
  55 or
  56 .BR getline (3).
  57
  58 The user's language preference is taken into account per the
  59 environment variables
  60 .BR LANG ,
  61 .BR LC_MESSAGES ,
  62 and
  63 .BR LC_ALL ,
  64 if the program has called
  65 .BR setlocale (3)
  66 to effect their changes.
  67
  68 Regardless of the locale, responses matching
  69 .B ^[Yy]
  70 are always accepted as affirmative, and those matching
  71 .B ^[Nn]
  72 are always accepted as negative.
  73 .SH RETURN VALUE
  74 After examining
  75 .IR response ,
  76 .BR rpmatch ()
  77 returns 0 for a recognized negative response ("no"), 1
  78 for a recognized positive response ("yes"), and \-1 when the value
  79 of
  80 .I response
  81 is unrecognized.
  82 .SH ERRORS
  83 A return value of \-1 may indicate either an invalid input, or some
  84 other error.
  85 It is incorrect to only test if the return value is nonzero.
  86
  87 .BR rpmatch ()
  88 can fail for any of the reasons that
  89 .BR regcomp (3)
  90 or
  91 .BR regexec (3)
  92 can fail; the cause of the error
  93 is not available from
  94 .I errno
  95 or anywhere else, but indicates a
  96 failure of the regex engine (but this case is indistinguishable from
  97 that of an unrecognized value of
  98 .IR response ).
  99 .SH ATTRIBUTES
 100 For an explanation of the terms used in this section, see
 101 .BR attributes (7).
 102 .TS
 103 allbox;
 104 lb lb lb
 105 l l l.
 106 Interface       Attribute       Value
 107 T{
 108 .BR rpmatch ()
 109 T}      Thread safety   MT-Safe locale
 110 .TE
 111
 112 .SH CONFORMING TO
 113 .BR rpmatch ()
 114 is not required by any standard, but
 115 is available on a few other systems.
 116 .\" It is available on at least AIX 5.1 and FreeBSD 6.0.
 117 .SH BUGS
 118 The
 119 .BR rpmatch ()
 120 implementation looks at only the first character
 121 of
 122 .IR response .
 123 As a consequence, "nyes" returns 0, and
 124 "ynever; not in a million years" returns 1.
 125 It would be preferable to accept input strings much more
 126 strictly, for example (using the extended regular
 127 expression notation described in
 128 .BR regex (7)):
 129 .B ^([yY]|yes|YES)$
 130 and
 131 .BR ^([nN]|no|NO)$ .
 132 .SH EXAMPLE
 133 The following program displays the results when
 134 .BR rpmatch ()
 135 is applied to the string given in the program's command-line argument.
 136 .nf
 137
 138 #define _SVID_SOURCE
 139 #include <locale.h>
 140 #include <stdlib.h>
 141 #include <string.h>
 142 #include <stdio.h>
 143
 144 int
 145 main(int argc, char *argv[])
 146 {
 147     if (argc != 2 || strcmp(argv[1], "\-\-help") == 0) {
 148         fprintf(stderr, "%s response\\n", argv[0]);
 149         exit(EXIT_FAILURE);
 150     }
 151
 152     setlocale(LC_ALL, "");
 153     printf("rpmatch() returns: %d\\n", rpmatch(argv[1]));
 154     exit(EXIT_SUCCESS);
 155 }
 156 .fi
 157 .SH SEE ALSO
 158 .BR fgets (3),
 159 .BR getline (3),
 160 .BR nl_langinfo (3),
 161 .BR regcomp (3),
 162 .BR setlocale (3)