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.

3 files changed, 12 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index 1c214d520..a57c4b36f 100644
--- a/NEWS
+++ b/NEWS
@@ -94,6 +94,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   pseudo file systems "bpf_fs", "btrfs_test", "nsfs", "overlayfs"
   and "tracefs", and remote file system "acfs".
 
+  wc now ensures a single line per file for counts on standard output,
+  by quoting names containing '\n' characters; appropriate for use in a shell.
+
 
 * Noteworthy changes in release 8.24 (2015-07-03) [stable]
 
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');
 }
 
diff --git a/tests/misc/wc-files0.sh b/tests/misc/wc-files0.sh
index b6a204c1c..4562e6a4e 100755
--- a/tests/misc/wc-files0.sh
+++ b/tests/misc/wc-files0.sh
@@ -40,4 +40,12 @@ if test "$fail" = ''; then
   compare exp out || fail=1
 fi
 
+# Ensure file name containing new lines are output on a single line
+nlname='1
+2'
+touch "$nlname" || framework_failure_
+printf '%s\0' "$nlname" | wc --files0-from=- > out || fail=1
+printf '%s\n' "0 0 0 '1'$'\\n''2'" > exp || framework_failure_
+compare exp out || fail=1
+
 Exit $fail