rpmatch(3)

NAME

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

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
   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

   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
   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

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(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
   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)$.

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 4.09 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/.

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