rpmatch(3)

1RPMATCH(3)                 Library Functions Manual                 RPMATCH(3)
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NAME

6       rpmatch - determine if the answer to a question is affirmative or nega‐
7       tive
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SYNOPSIS

10       #define _SVID_SOURCE
11       #include <stdlib.h>
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13       int rpmatch (const char *response);
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DESCRIPTION

16       rpmatch() handles a user response to yes or no questions, with  support
17       for internationalization.
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19       response  should be a null-terminated string containing a user-supplied
20       response, perhaps obtained with fgets(3) or getline(3).
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22       The user's language preference is taken into account per  the  environ‐
23       ment variables LANG, LC_MESSAGES, and LC_ALL, if the program has called
24       setlocale() to effect their changes.
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26       Regardless of the locale, responses matching ^[Yy] are always  accepted
27       as  affirmative,  and those matching ^[Nn] are always accepted as nega‐
28       tive.
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RETURN VALUE

31       After examining response, rpmatch() returns 0 for a recognized negative
32       response  ("no"),  1 for a recognized positive response ("yes"), and -1
33       when the value of response is unrecognized.
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ERRORS

36       A return value of -1 may indicate either  an  invalid  input,  or  some
37       other  error.   It  is  incorrect  to  only test if the return value is
38       nonzero.
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40       rpmatch() can fail for any of the reasons that regcomp(3) or regexec(3)
41       can  fail;  the  cause of the error is not available from errno or any‐
42       where else, but indicates a failure of the regex engine (but this  case
43       is indistinguishable from that of an unrecognized value of response).
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CONFORMING TO

46       rpmatch()  is  not  required by any standard, but is available on a few
47       other systems.
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BUGS

50       The rpmatch() implementation looks  at  only  the  first  character  of
51       response.   As  a  consequence, "nyes" returns 0, and "ynever; not in a
52       million years" returns 1.  It  would  be  preferable  to  accept  input
53       strings  much  more  strictly,  for example (using the extended regular
54       expression  notation  described  in  regex(7)):  ^([yY]|yes|YES)$   and
55       ^([nN]|no|NO)$.
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EXAMPLE

58       The following program displays the results when rpmatch() is applied to
59       the string given in the program's command-line argument.
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61       #define _SVID_SOURCE
62       #include <locale.h>
63       #include <stdlib.h>
64       #include <string.h>
65       #include <stdio.h>
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67       int
68       main(int argc, char *argv[])
69       {
70           if (argc != 2 || strcmp(argv[1], "--help") == 0) {
71               fprintf(stderr, "%s response\n", argv[0]);
72               exit(EXIT_FAILURE);
73           }
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75           setlocale(LC_ALL, "");
76           printf("rpmatch() returns: %d\n", rpmatch(argv[1]));
77           exit(EXIT_SUCCESS);
78       }
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