Automerge from mysql-5.1 for follow-up bug#57450.

client/mysql.cc

@@ -1127,6 +1127,8 @@ int main(int argc,char *argv[])
   if (status.batch && !status.line_buff &&
       !(status.line_buff= batch_readline_init(MAX_BATCH_BUFFER_SIZE, stdin)))
   {
+    put_info("Can't initialize batch_readline - may be the input source is "
+             "a directory or a block device.", INFO_ERROR, 0);
     free_defaults(defaults_argv);
     my_end(0);
     exit(1);

client/readline.cc

@@ -18,6 +18,7 @@
 #include <my_global.h>
 #include <my_sys.h>
 #include <m_string.h>
+#include <my_dir.h>
 #include "my_readline.h"
 
 static bool init_line_buffer(LINE_BUFFER *buffer,File file,ulong size,
@@ -30,6 +31,13 @@ static char *intern_read_line(LINE_BUFFER *buffer, ulong *out_length);
 LINE_BUFFER *batch_readline_init(ulong max_size,FILE *file)
 {
   LINE_BUFFER *line_buff;
+  MY_STAT input_file_stat;
+
+  if (my_fstat(fileno(file), &input_file_stat, MYF(MY_WME)) ||
+      MY_S_ISDIR(input_file_stat.st_mode) ||
+      MY_S_ISBLK(input_file_stat.st_mode))
+    return 0;
+
   if (!(line_buff=(LINE_BUFFER*)
         my_malloc(sizeof(*line_buff),MYF(MY_WME | MY_ZEROFILL))))
     return 0;