>From 81e589021d9c47e4fbc4284e82881a9703246476 Mon Sep 17 00:00:00 2001
From: Bernhard Voelker <address@hidden>
Date: Thu, 14 Apr 2016 12:38:09 +0200
Subject: [PATCH 1/2] seq: do not allow 0 as increment value
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* src/seq.c (main): Exit with an error diagnostic when the given
step value is Zero.
(usage): Document it.
* doc/coreutils.texi (seq invocation): Likewise.
* tests/misc/seq.pl: Add tests.
* NEWS (Changes in behavior): Mention the change.
Reported by Маренков Евгений in:
http://bugs.gnu.org/23110
---
 NEWS               |  2 ++
 doc/coreutils.texi |  2 ++
 src/seq.c          |  8 ++++++++
 tests/misc/seq.pl  | 10 ++++++++++
 4 files changed, 22 insertions(+)

diff --git a/NEWS b/NEWS
index 9445977..13af702 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Changes in behavior
 
+   seq no longer accepts 0 value as increment argument.
+
    stat now outputs nanosecond information for time stamps even if
    they are out of localtime range.
 
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 45706bd..6b70635 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -17422,6 +17422,8 @@ even when @var{first} is larger than @var{last}.
 The sequence of numbers ends when the sum of the current number and
 @var{increment} would become greater than @var{last},
 so @code{seq 1 10 10} only produces @samp{1}.
address@hidden must not be @samp{0}; use @command{yes} to get
+repeated output of a constant number.
 Floating-point numbers may be specified.  @xref{Floating point}.
 
 The program accepts the following options.  Also see @ref{Common options}.
diff --git a/src/seq.c b/src/seq.c
index fbb94a0..91cf625 100644
--- a/src/seq.c
+++ b/src/seq.c
@@ -92,6 +92,7 @@ INCREMENT would become greater than LAST.\n\
 FIRST, INCREMENT, and LAST are interpreted as floating point values.\n\
 INCREMENT is usually positive if FIRST is smaller than LAST, and\n\
 INCREMENT is usually negative if FIRST is greater than LAST.\n\
+INCREMENT must not be 0.\n\
 "), stdout);
       fputs (_("\
 FORMAT must be suitable for printing one argument of type 'double';\n\
@@ -635,6 +636,13 @@ main (int argc, char **argv)
       if (optind < argc)
         {
           step = last;
+          if (step.value == 0)
+            {
+              error (0, 0, _("invalid Zero increment value: %s"),
+                     quote (argv[optind-1]));
+              usage (EXIT_FAILURE);
+            }
+
           last = scan_arg (argv[optind++]);
         }
     }
diff --git a/tests/misc/seq.pl b/tests/misc/seq.pl
index 6564415..ac0664f 100755
--- a/tests/misc/seq.pl
+++ b/tests/misc/seq.pl
@@ -25,6 +25,7 @@ use strict;
 
 my $prog = 'seq';
 my $try_help = "Try '$prog --help' for more information.\n";
+my $err_inc_zero = "seq: invalid Zero increment value: '0'\n".$try_help;
 
 my $locale = $ENV{LOCALE_FR_UTF8};
 ! defined $locale || $locale eq 'none'
@@ -151,6 +152,15 @@ my @Tests =
    ['fast-1', qw(4), {OUT => [qw(1 2 3 4)]}],
    ['fast-2', qw(1 4), {OUT => [qw(1 2 3 4)]}],
    ['fast-3', qw(1 1 4), {OUT => [qw(1 2 3 4)]}],
+
+   # Ensure an INCREMENT of Zero is rejected.
+   ['inc-zero-1',	qw(1 0 10), {EXIT => 1}, {ERR => $err_inc_zero}],
+   ['inc-zero-2',	qw(0 -0 0), {EXIT => 1}, {ERR => $err_inc_zero},
+    {ERR_SUBST => 's/-0/0/'}],
+   ['inc-zero-3',	qw(1 0.0 10), {EXIT => 1},{ERR => $err_inc_zero},
+    {ERR_SUBST => 's/0.0/0/'}],
+   ['inc-zero-4',	qw(1 -0.0e-10 10), {EXIT => 1},{ERR => $err_inc_zero},
+    {ERR_SUBST => 's/-0\.0e-10/0/'}],
   );
 
 # Append a newline to each entry in the OUT array.
-- 
2.1.4