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(): _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).
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 3.24 of the Linux man-pages project. A
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be found at http://www.kernel.org/doc/man-pages/.