rpmatch - determine if the answer to a question is affirmative or negative
#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
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.
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.
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).
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| rpmatch () |
Thread safety |
MT-Safe locale |
rpmatch() is not required by any standard, but is available on a few
other systems.
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)$.
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);
}
fgets(3),
getline(3),
nl_langinfo(3),
regcomp(3),
setlocale(3)