grep: Fix -f FILE when FILE is empty and -x provided

Grep currently special-cased empty pattern file to be the same as
pattern file with one empty line (empty pattern). That does mirror how
GNU grep behaves, except when -x is provided. In that case .* pattern
needs to be used instead.

Signed-off-by: Gray Wolf <wolf@wolfsden.cz>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 9 insertions, 2 deletions

diff --git a/findutils/grep.c b/findutils/grep.c
index 5b8644c36..84a6f7b1c 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -762,8 +762,9 @@ int grep_main(int argc UNUSED_PARAM, char **argv)
         if (option_mask32 & OPT_f) {
                 load_regexes_from_file(fopt);
                 if (!pattern_head) { /* -f EMPTY_FILE? */
-                        /* GNU grep treats it as "nothing matches" */
-                        llist_add_to(&pattern_head, new_grep_list_data((char*) "", 0));
+                        /* GNU grep treats it as "nothing matches" except when -x */
+                        const char *data = (option_mask32 & OPT_x) ? ".*" : "";
+                        llist_add_to(&pattern_head, new_grep_list_data((char*)data, 0));
                         invert_search ^= 1;
                 }
         }
diff --git a/testsuite/grep.tests b/testsuite/grep.tests
index 26f8e69cf..9c1f35499 100755
--- a/testsuite/grep.tests
+++ b/testsuite/grep.tests
@@ -129,6 +129,12 @@ testing "grep -v -f EMPTY_FILE" \
         "" \
         "test\n"
 
+testing "grep -vxf EMPTY_FILE" \
+        "grep -vxf input" \
+        "test\n" \
+        "" \
+        "test\n"
+
 testing "grep -Fw matches only words" \
         "grep -Fw foo input" \
         "" \