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
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  29 .TH RPMATCH 3 2017-09-15 "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 .PP
  36 .BI "int rpmatch(const char *" response );
  37 .fi
  38 .PP
  39 .in -4n
  40 Feature Test Macro Requirements for glibc (see
  41 .BR feature_test_macros (7)):
  42 .in
  43 .PP
  44 .BR rpmatch ():
  45     Since glibc 2.19:
  46         _DEFAULT_SOURCE
  47     Glibc 2.19 and earlier:
  48         _SVID_SOURCE
  49 .SH DESCRIPTION
  50 .BR rpmatch ()
  51 handles a user response to yes or no questions, with
  52 support for internationalization.
  53 .PP
  54 .I response
  55 should be a null-terminated string containing a
  56 user-supplied response, perhaps obtained with
  57 .BR fgets (3)
  58 or
  59 .BR getline (3).
  60 .PP
  61 The user's language preference is taken into account per the
  62 environment variables
  63 .BR LANG ,
  64 .BR LC_MESSAGES ,
  65 and
  66 .BR LC_ALL ,
  67 if the program has called
  68 .BR setlocale (3)
  69 to effect their changes.
  70 .PP
  71 Regardless of the locale, responses matching
  72 .B ^[Yy]
  73 are always accepted as affirmative, and those matching
  74 .B ^[Nn]
  75 are always accepted as negative.
  76 .SH RETURN VALUE
  77 After examining
  78 .IR response ,
  79 .BR rpmatch ()
  80 returns 0 for a recognized negative response ("no"), 1
  81 for a recognized positive response ("yes"), and \-1 when the value
  82 of
  83 .I response
  84 is unrecognized.
  85 .SH ERRORS
  86 A return value of \-1 may indicate either an invalid input, or some
  87 other error.
  88 It is incorrect to only test if the return value is nonzero.
  89 .PP
  90 .BR rpmatch ()
  91 can fail for any of the reasons that
  92 .BR regcomp (3)
  93 or
  94 .BR regexec (3)
  95 can fail; the cause of the error
  96 is not available from
  97 .I errno
  98 or anywhere else, but indicates a
  99 failure of the regex engine (but this case is indistinguishable from
 100 that of an unrecognized value of
 101 .IR response ).
 102 .SH ATTRIBUTES
 103 For an explanation of the terms used in this section, see
 104 .BR attributes (7).
 105 .TS
 106 allbox;
 107 lb lb lb
 108 l l l.
 109 Interface       Attribute       Value
 110 T{
 111 .BR rpmatch ()
 112 T}      Thread safety   MT-Safe locale
 113 .TE
 114 .sp 1
 115 .SH CONFORMING TO
 116 .BR rpmatch ()
 117 is not required by any standard, but
 118 is available on a few other systems.
 119 .\" It is available on at least AIX 5.1 and FreeBSD 6.0.
 120 .SH BUGS
 121 The
 122 .BR rpmatch ()
 123 implementation looks at only the first character
 124 of
 125 .IR response .
 126 As a consequence, "nyes" returns 0, and
 127 "ynever; not in a million years" returns 1.
 128 It would be preferable to accept input strings much more
 129 strictly, for example (using the extended regular
 130 expression notation described in
 131 .BR regex (7)):
 132 .B ^([yY]|yes|YES)$
 133 and
 134 .BR ^([nN]|no|NO)$ .
 135 .SH EXAMPLE
 136 The following program displays the results when
 137 .BR rpmatch ()
 138 is applied to the string given in the program's command-line argument.
 139 .PP
 140 .EX
 141 #define _SVID_SOURCE
 142 #include <locale.h>
 143 #include <stdlib.h>
 144 #include <string.h>
 145 #include <stdio.h>
 146
 147 int
 148 main(int argc, char *argv[])
 149 {
 150     if (argc != 2 || strcmp(argv[1], "\-\-help") == 0) {
 151         fprintf(stderr, "%s response\\n", argv[0]);
 152         exit(EXIT_FAILURE);
 153     }
 154
 155     setlocale(LC_ALL, "");
 156     printf("rpmatch() returns: %d\\n", rpmatch(argv[1]));
 157     exit(EXIT_SUCCESS);
 158 }
 159 .EE
 160 .SH SEE ALSO
 161 .BR fgets (3),
 162 .BR getline (3),
 163 .BR nl_langinfo (3),
 164 .BR regcomp (3),
 165 .BR setlocale (3)