rpmatch(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | BUGS | EXAMPLES | SEE ALSO | COLOPHON

rpmatch(3)              Library Functions Manual              rpmatch(3)

NAME         top

       rpmatch - determine if the answer to a question is affirmative or
       negative

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdlib.h>

       int rpmatch(const char *response);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       rpmatch():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           glibc 2.19 and earlier:
               _SVID_SOURCE

DESCRIPTION         top

       rpmatch() handles a user response to yes or no questions, with
       support for internationalization.

       response should be a null-terminated string containing a user-
       supplied response, perhaps obtained with fgets(3) or getline(3).

       The user's language preference is taken into account per the
       environment variables LANG, LC_MESSAGES, and LC_ALL, if the
       program has called setlocale(3) to effect their changes.

       Regardless of the locale, responses matching ^[Yy] are always
       accepted as affirmative, and those matching ^[Nn] are always
       accepted as negative.

RETURN VALUE         top

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

ERRORS         top

       A return value of -1 may indicate either an invalid input, or
       some other error.  It is incorrect to only test if the return
       value is nonzero.

       rpmatch() can fail for any of the reasons that regcomp(3) or
       regexec(3) can fail; the cause of the error is not available from
       errno or anywhere else, but indicates a failure of the regex
       engine (but this case is indistinguishable from that of an
       unrecognized value of response).

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌──────────────────────────────┬───────────────┬────────────────┐
       │ Interface                    Attribute     Value          │
       ├──────────────────────────────┼───────────────┼────────────────┤
       │ rpmatch()                    │ Thread safety │ MT-Safe locale │
       └──────────────────────────────┴───────────────┴────────────────┘

STANDARDS         top

       None.

HISTORY         top

       GNU, FreeBSD, AIX.

BUGS         top

       The YESEXPR and NOEXPR of some locales (including "C") only
       inspect the first character of the response.  This can mean that
       "yno" et al. resolve to 1.  This is an unfortunate historical
       side-effect which should be fixed in time with proper
       localisation, and should not deter from rpmatch() being the
       proper way to distinguish between binary answers.

EXAMPLES         top

       The following program displays the results when rpmatch() is
       applied to the string given in the program's command-line
       argument.

       #define _DEFAULT_SOURCE
       #include <locale.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>

       int
       main(int argc, char *argv[])
       {
           if (argc != 2 || strcmp(argv[1], "--help") == 0) {
               fprintf(stderr, "%s response\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           setlocale(LC_ALL, "");
           printf("rpmatch() returns: %d\n", rpmatch(argv[1]));
           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       fgets(3), getline(3), nl_langinfo(3), regcomp(3), setlocale(3)

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
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       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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Linux man-pages 6.9.1          2024-06-15                     rpmatch(3)

Pages that refer to this page: setlocale(3)locale(7)