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

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

SYNOPSIS
       #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
       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  environ-
       ment 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 nega-
       tive.

RETURN VALUE
       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
       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 non-
       zero.

       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 any-
       where else, but indicates a failure of the regex engine (but this  case
       is indistinguishable from that of an unrecognized value of response).

ATTRIBUTES
       For  an  explanation  of  the  terms  used  in  this  section,  see at-
       tributes(7).

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

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

BUGS
       The  rpmatch()  implementation looks at only the first character of re-
       sponse.  As a consequence, "nyes" returns 0, and "ynever; not in a mil-
       lion  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)$.

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

       #define _SVID_SOURCE
       #include <locale.h>
       #include <stdlib.h>
       #include <string.h>
       #include <stdio.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
       fgets(3), getline(3), nl_langinfo(3), regcomp(3), setlocale(3)

COLOPHON
       This page is part of release 5.05 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
       https://www.kernel.org/doc/man-pages/.

GNU                               2019-03-06                        RPMATCH(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | BUGS | EXAMPLE | SEE ALSO | COLOPHON