Teach -o to print ranges that produce zero length matches.

And fix one test for NUL that should be a length test for -z support

2 files changed, 11 insertions, 6 deletions

diff --git a/tests/grep.test b/tests/grep.test
index c6171112..215491c2 100755
--- a/tests/grep.test
+++ b/tests/grep.test
@@ -199,3 +199,6 @@ testing "-Fix" "grep -Fix h input" "H\nh\n" \
   "missing\nH\nthis is HELLO\nthis is WORLD\nh\nmissing" ""
 testing "-f /dev/null" "grep -f /dev/null" "" "" "hello\n"
 testing "-z with \n in pattern" "grep -f input" "hi\nthere\n" "i\nt" "hi\nthere"
+
+testing "print zero length match" "grep '[0-9]*'" "abc\n" "" "abc\n"
+testing "-o skip zero length match" "grep -o '[0-9]*'" "1234\n" "" "a1234b"
diff --git a/toys/posix/grep.c b/toys/posix/grep.c
index 2ddb6b93..cd8928a1 100644
--- a/toys/posix/grep.c
+++ b/toys/posix/grep.c
@@ -218,8 +218,12 @@ static void do_grep(int fd, char *name)
         }
       }
 
-      if (!rc && FLAG(x))
-        if (mm->rm_so || line[mm->rm_eo]) rc = 1;
+      if (!rc && FLAG(o) && !mm->rm_eo && ulen>start-line) {
+        start++;
+        continue;
+      }
+
+      if (!rc && FLAG(x) && (mm->rm_so || ulen-(start-line)!=mm->rm_eo)) rc = 1;
 
       if (!rc && FLAG(w)) {
         char c = 0;
@@ -240,10 +244,8 @@ static void do_grep(int fd, char *name)
 
       if (FLAG(v)) {
         if (FLAG(o)) {
-          if (rc) {
-            mm->rm_so = 0;
-            mm->rm_eo = ulen-(start-line);
-          } else if (!mm->rm_so) {
+          if (rc) mm->rm_eo = ulen-(start-line);
+          else if (!mm->rm_so) {
             start += mm->rm_eo;
             continue;
           } else mm->rm_eo = mm->rm_so;