rpmatch(3) Library Functions Manual rpmatch(3)
NAME
rpmatch - determine if the answer to a question is affirmative or nega-
tive
LIBRARY
Standard C library (libc, -lc)
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 │
└─────────────────────────────────────┴───────────────┴────────────────┘
STANDARDS
rpmatch() is not required by any standard, but available under the GNU
C library, FreeBSD, and AIX.
BUGS
The YESEXPR and NOEXPR of some locales (including "C") only inspect the
first character of the response. This can mean that "yno" et al. re-
solve to 1. This is an unfortunate historical side-effect which should
be fixed in time with proper localisation, and should not deter from
rpmatch() being the proper way to distinguish between binary answers.
EXAMPLES
The following program displays the results when rpmatch() is applied to
the string given in the program's command-line argument.
#define _DEFAULT_SOURCE
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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)
Linux man-pages 6.03 2023-02-05 rpmatch(3)
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