1RPMATCH(3) Linux Programmer's Manual RPMATCH(3)
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6 rpmatch - determine if the answer to a question is affirmative or nega‐
7 tive
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10 #include <stdlib.h>
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12 int rpmatch(const char *response);
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14 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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16 rpmatch():
17 Since glibc 2.19:
18 _DEFAULT_SOURCE
19 Glibc 2.19 and earlier:
20 _SVID_SOURCE
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23 rpmatch() handles a user response to yes or no questions, with support
24 for internationalization.
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26 response should be a null-terminated string containing a user-supplied
27 response, perhaps obtained with fgets(3) or getline(3).
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29 The user's language preference is taken into account per the environ‐
30 ment variables LANG, LC_MESSAGES, and LC_ALL, if the program has called
31 setlocale(3) to effect their changes.
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33 Regardless of the locale, responses matching ^[Yy] are always accepted
34 as affirmative, and those matching ^[Nn] are always accepted as nega‐
35 tive.
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38 After examining response, rpmatch() returns 0 for a recognized negative
39 response ("no"), 1 for a recognized positive response ("yes"), and -1
40 when the value of response is unrecognized.
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43 A return value of -1 may indicate either an invalid input, or some
44 other error. It is incorrect to only test if the return value is non‐
45 zero.
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47 rpmatch() can fail for any of the reasons that regcomp(3) or regexec(3)
48 can fail; the cause of the error is not available from errno or any‐
49 where else, but indicates a failure of the regex engine (but this case
50 is indistinguishable from that of an unrecognized value of response).
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53 For an explanation of the terms used in this section, see at‐
54 tributes(7).
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56 ┌─────────────────────────────────────┬───────────────┬────────────────┐
57 │Interface │ Attribute │ Value │
58 ├─────────────────────────────────────┼───────────────┼────────────────┤
59 │rpmatch() │ Thread safety │ MT-Safe locale │
60 └─────────────────────────────────────┴───────────────┴────────────────┘
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63 rpmatch() is not required by any standard, but is available on a few
64 other systems.
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67 The rpmatch() implementation looks at only the first character of re‐
68 sponse. As a consequence, "nyes" returns 0, and "ynever; not in a mil‐
69 lion years" returns 1. It would be preferable to accept input strings
70 much more strictly, for example (using the extended regular expression
71 notation described in regex(7)): ^([yY]|yes|YES)$ and ^([nN]|no|NO)$.
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74 The following program displays the results when rpmatch() is applied to
75 the string given in the program's command-line argument.
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77 #define _SVID_SOURCE
78 #include <locale.h>
79 #include <stdlib.h>
80 #include <string.h>
81 #include <stdio.h>
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83 int
84 main(int argc, char *argv[])
85 {
86 if (argc != 2 || strcmp(argv[1], "--help") == 0) {
87 fprintf(stderr, "%s response\n", argv[0]);
88 exit(EXIT_FAILURE);
89 }
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91 setlocale(LC_ALL, "");
92 printf("rpmatch() returns: %d\n", rpmatch(argv[1]));
93 exit(EXIT_SUCCESS);
94 }
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97 fgets(3), getline(3), nl_langinfo(3), regcomp(3), setlocale(3)
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100 This page is part of release 5.13 of the Linux man-pages project. A
101 description of the project, information about reporting bugs, and the
102 latest version of this page, can be found at
103 https://www.kernel.org/doc/man-pages/.
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107GNU 2021-03-22 RPMATCH(3)