.\" Copyright (C) 2006 Justin Pryzby <pryzbyj@justinpryzby.com>

.\"

.\" %%%LICENSE_START(PERMISSIVE_MISC)

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.\" distribute, sublicense, and/or sell copies of the Software, and to

.\" permit persons to whom the Software is furnished to do so, subject to

.\" the following conditions:

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.\" The above copyright notice and this permission notice shall be

.\" included in all copies or substantial portions of the Software.

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.\"

.\" References:

.\"   glibc manual and source

.\"

.\" 2006-05-19, mtk, various edits and example program

.\"

.TH RPMATCH 3 2017-09-15 "GNU" "Linux Programmer's Manual"

.SH NAME

rpmatch \- determine if the answer to a question is affirmative or negative

.SH SYNOPSIS

.nf

.B #include <stdlib.h>

.PP

.BI "int rpmatch(const char *" response );

.fi

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.BR rpmatch ():

    Since glibc 2.19:

        _DEFAULT_SOURCE

    Glibc 2.19 and earlier:

        _SVID_SOURCE

.SH DESCRIPTION

.BR rpmatch ()

handles a user response to yes or no questions, with

support for internationalization.

.PP

.I response

should be a null-terminated string containing a

user-supplied response, perhaps obtained with

.BR fgets (3)

or

.BR getline (3).

.PP

The user's language preference is taken into account per the

environment variables

.BR LANG ,

.BR LC_MESSAGES ,

and

.BR LC_ALL ,

if the program has called

.BR setlocale (3)

to effect their changes.

.PP

Regardless of the locale, responses matching

.B ^[Yy]

are always accepted as affirmative, and those matching

.B ^[Nn]

are always accepted as negative.

.SH RETURN VALUE

After examining

.IR response ,

.BR rpmatch ()

returns 0 for a recognized negative response ("no"), 1

for a recognized positive response ("yes"), and \-1 when the value

of

.I response

is unrecognized.

.SH 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.

.PP

.BR rpmatch ()

can fail for any of the reasons that

.BR regcomp (3)

or

.BR regexec (3)

can fail; the cause of the error

is not available from

.I errno

or anywhere else, but indicates a

failure of the regex engine (but this case is indistinguishable from

that of an unrecognized value of

.IR response ).

.SH ATTRIBUTES

For an explanation of the terms used in this section, see

.BR attributes (7).

.TS

allbox;

lb lb lb

l l l.

Interface	Attribute	Value

T{

.BR rpmatch ()

T}	Thread safety	MT-Safe locale

.TE

.sp 1

.SH CONFORMING TO

.BR rpmatch ()

is not required by any standard, but

is available on a few other systems.

.\" It is available on at least AIX 5.1 and FreeBSD 6.0.

.SH BUGS

The

.BR rpmatch ()

implementation looks at only the first character

of

.IR 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

.BR regex (7)):

.B ^([yY]|yes|YES)$

and

.BR ^([nN]|no|NO)$ .

.SH EXAMPLE

The following program displays the results when

.BR rpmatch ()

is applied to the string given in the program's command-line argument.

.PP

.EX

#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);

}

.EE

.SH SEE ALSO

.BR fgets (3),

.BR getline (3),

.BR nl_langinfo (3),

.BR regcomp (3),

.BR setlocale (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.