NAME
rpmatch - determine if the answer to a question is affirmative or negative
SYNOPSIS
#define _SVID_SOURCE
#include <stdlib.h>
int rpmatch(const char *response);
DESCRIPTION
R 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
R response ,
R 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.
R 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
R rpmatch ()
is not required by any standard, but
is available on a few other systems.
BUGS
The
R 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
R 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
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