---
name: "rpmatch"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/rpmatch"
---

# rpmatch(3)

determine if the answer to a question is affirmative or negative

## 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)](/feature_test_macros/7.md)):

**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)](/fgets/3.md) or [**getline**(3)](/getline/3.md).

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)](/setlocale/3.md) 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 *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)](/regcomp/3.md) or [**regexec**(3)](/regexec/3.md) can fail; 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)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **rpmatch**() | Thread safety | MT-Safe locale |

## STANDARDS

None.

## HISTORY

GNU, FreeBSD, 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>
#define streq(...)  (strcmp(__VA_ARGS__) == 0)
int
main(int argc, char *argv[])
{
    if (argc != 2 || streq(argv[1], "--help")) {
        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)](/fgets/3.md), [**getline**(3)](/getline/3.md), [**nl\_langinfo**(3)](/nl_langinfo/3.md), [**regcomp**(3)](/regcomp/3.md), [**setlocale**(3)](/setlocale/3.md)