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   to get outdated.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 <ferivoz@riseup.net>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/configure.ac b/configure.ac
index f4c29ca46109f85161347f6b4b05b9c403394088..d75b99ff5634ca5351f8f4c028f1e610bc91ac57 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -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)
 AC_SYS_LARGEFILE
 

diff --git a/libmisc/yesno.c b/libmisc/yesno.c
index d8847e40e377bfadbc312fe26c780cf967985a7f..2ef4d9fab79182050ef3b525b4001a4b309ad8df 100644 (file)
--- a/libmisc/yesno.c
+++ b/libmisc/yesno.c
@@ -1,59 +1,84 @@
 /*
  * SPDX-FileCopyrightText: 1992 - 1994, Julianne Frances Haugh
  * SPDX-FileCopyrightText: 2007 - 2008, Nicolas François
+ * SPDX-FileCopyrightText: 2023, Alejandro Colomar <alx@kernel.org>
  *
  * 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
+ * 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.
  *
- *     It returns false if no.
+ * Description
+ *     After a yes/no question, this function gets the answer from the
+ *     user.
  *
- *     If the read_only flag is set, it will print No, and will return
- *     false.
+ *     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)
  */
-bool yes_or_no (bool read_only)
+
+
+#if !defined(HAVE_RPMATCH)
+static int rpmatch(const char *response);
+#endif
+
+
+bool
+yes_or_no(bool read_only)
 {
-       int c;
-       bool result;
+       bool  ret;
+       char  *buf;
 
-       /*
-        * In read-only mode all questions are answered "no".
-        */
        if (read_only) {
-               (void) puts (_("No"));
+               puts(_("No"));
                return false;
        }
 
-       /*
-        * Typically, there's a prompt on stdout, sometimes unflushed.
-        */
-       (void) fflush (stdout);
+       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;
+       free(buf);
+       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;
+}
+#endif