rpmatch
Section: C Library Functions (3)
Updated: 2023-02-05
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NAME
rpmatch - determine if the answer to a question is affirmative or negative
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
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
ha[Yy]
are always accepted as affirmative, and those matching
ha[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
|
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. resolve 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)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- STANDARDS
-
- BUGS
-
- EXAMPLES
-
- SEE ALSO
-
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