libmisc/yesno.c: Use getline(3) and rpmatch(3)

getline(3) is much more readable than manually looping.  It has some
overhead due to the allocation of a buffer, but that shouldn't be a
problem here.  If that was a problem, we could reuse the buffer (thus
making the function non-reentrant), but I don't think that's worth the
extra complexity.

Using rpmatch(3) instead of a simple y/n test provides i18n to the
response checking.  We have a fall-back minimalistic implementation for
systems that lack this function (e.g., musl libc).

While we're at it, apply some other minor improvements to this file:

-  Remove comment saying which files use this function.  That's likely
   to get outdated.  And anyway, it's just a grep(1) away, so it doesn't
   really add any value.

-  Remove unnecessary casts to (void) that were used to verbosely ignore
   errors from stdio calls.  They add clutter without really adding much
   value to the code (or I don't see it).

-  Remove comments from the function body.  They make the function less
   readable.  Instead, centralize the description of the function into a
   man-page-like comment before the function definition.  This keeps the
   function body short and sweet.

-  Add '#include <stdbool.h>', which was missing.

-  Minor whitespace style changes (it doesn't hurt the diff at this
   point, since most of the affected lines were already touched by other
   changes, so I applied my preferred style :).

Acked-by: Samanta Navarro <>
Cc: Serge Hallyn <>
Signed-off-by: Alejandro Colomar <>
This commit is contained in:
Alejandro Colomar 2023-04-22 01:59:33 +02:00 committed by Serge Hallyn
parent 7b686d8bd6
commit e28deeb8e9
2 changed files with 61 additions and 35 deletions

View File

@ -50,6 +50,7 @@ AC_CHECK_FUNCS(arc4random_buf futimes \
initgroups lckpwdf lutimes mempcpy \
setgroups updwtmp updwtmpx innetgr \
getspnam_r \
rpmatch \
memset_explicit explicit_bzero stpecpy stpeprintf)

View File

@ -1,59 +1,84 @@
* SPDX-FileCopyrightText: 1992 - 1994, Julianne Frances Haugh
* SPDX-FileCopyrightText: 2007 - 2008, Nicolas François
* SPDX-FileCopyrightText: 2023, Alejandro Colomar <>
* SPDX-License-Identifier: BSD-3-Clause
* Common code for yes/no prompting
* Used by pwck.c and grpck.c
#include <config.h>
#ident "$Id$"
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include "prototypes.h"
* yes_or_no - get answer to question from the user
* It returns false if no.
* If the read_only flag is set, it will print No, and will return
* false.
bool yes_or_no (bool read_only)
int c;
bool result;
* In read-only mode all questions are answered "no".
* Synopsis
* bool yes_or_no(bool read_only);
* Arguments
* read_only
* In read-only mode, all questions are answered "no". It
* will print "No" to stdout.
* Description
* After a yes/no question, this function gets the answer from the
* user.
* Calls to this function will normally be preceeded by a prompt on
* stdout, so we should fflush(3).
* Return value
* false "no"
* true "yes"
* See also
* rpmatch(3)
#if !defined(HAVE_RPMATCH)
static int rpmatch(const char *response);
yes_or_no(bool read_only)
bool ret;
char *buf;
if (read_only) {
(void) puts (_("No"));
return false;
* Typically, there's a prompt on stdout, sometimes unflushed.
(void) fflush (stdout);
* Get a line and see what the first character is.
c = fgetc(stdin);
/* TODO: use gettext */
result = (c == 'y' || c == 'Y');
ret = false;
if (getline(&buf, NULL, stdin) != NULL)
ret = rpmatch(buf) == 1;
while (c != '\n' && c != EOF)
c = fgetc(stdin);
return result;
return ret;
#if !defined(HAVE_RPMATCH)
static int
rpmatch(const char *response)
if (response[0] == 'y' || response[0] == 'Y')
return 1;
if (response[0] == 'n' || response[0] == 'n')
return 0;
return -1;