wc: avoid ambiguous output with '\n' in file names

* src/wc.c (write_counts): Shell escape the file name
if it contains '\n' so only a single line per file is output.
* tests/misc/wc-files0.sh: Add a test case.
* NEWS: Mention the improvement.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/wc.c b/src/wc.c
index c2a9c3fbe..94cbaff9a 100644
--- a/src/wc.c
+++ b/src/wc.c
@@ -182,7 +182,7 @@ write_counts (uintmax_t lines,
       printf (format_int, number_width, umaxtostr (linelength, buf));
     }
   if (file)
-    printf (" %s", file);
+    printf (" %s", strchr (file, '\n') ? quotef (file) : file);
   putchar ('\n');
 }