seq: fix to always honor the step value

* src/seq.c (main): With 3 positive integer args we were
checking the end value was == "1", rather than the step value.
* tests/misc/seq.pl: Add tests for this case.
Reported by Marcel Böhme in http://bugs.gnu.org/13525

1 files changed, 3 insertions, 2 deletions

diff --git a/src/seq.c b/src/seq.c
index 5ad5fad94..acbe2350a 100644
--- a/src/seq.c
+++ b/src/seq.c
@@ -565,11 +565,12 @@ main (int argc, char **argv)
      then use the much more efficient integer-only code.  */
   if (all_digits_p (argv[optind])
       && (n_args == 1 || all_digits_p (argv[optind + 1]))
-      && (n_args < 3 || STREQ ("1", argv[optind + 2]))
+      && (n_args < 3 || (STREQ ("1", argv[optind + 1])
+                         && all_digits_p (argv[optind + 2])))
       && !equal_width && !format_str && strlen (separator) == 1)
     {
       char const *s1 = n_args == 1 ? "1" : argv[optind];
-      char const *s2 = n_args == 1 ? argv[optind] : argv[optind + 1];
+      char const *s2 = argv[optind + (n_args - 1)];
       if (seq_fast (s1, s2))
         exit (EXIT_SUCCESS);