rpmatch(3) — Linux manual page


RPMATCH(3)              Linux Programmer's Manual             RPMATCH(3)

NAME         top

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

SYNOPSIS         top

       #include <stdlib.h>

       int rpmatch(const char *response);

   Feature Test Macro Requirements for glibc (see

           Since glibc 2.19:
           Glibc 2.19 and earlier:

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

       │Interface                      Attribute     Value          │
       │rpmatch()                      │ Thread safety │ MT-Safe locale │

CONFORMING TO         top

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

BUGS         top

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

EXAMPLES         top

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

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

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

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

GNU                            2021-03-22                     RPMATCH(3)

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