pintos: Fix undefined value warning from Perl on read error.

When sysread encounters an error, it returns undef, which yields a warning
when compared against 0.  This fixes the problem.

diff --git a/src/utils/pintos b/src/utils/pintos
index eca4708516e41f3c715d2145e761ba775036ed6a..156421649d943356fe69e2447e55a307bf84fd91 100755 (executable)
--- a/src/utils/pintos
+++ b/src/utils/pintos
@@ -827,8 +827,8 @@ sub xsystem {
 
                # Read and print out pipe data.
                my ($len) = length ($buf);
-               waitpid ($pid, 0), last
-                 if sysread ($in, $buf, 4096, $len) <= 0;
+               my ($n_read) = sysread ($in, $buf, 4096, $len);
+               waitpid ($pid, 0), last if !defined ($n_read) || $n_read <= 0;
                print substr ($buf, $len);
 
                # Remove full lines from $buf and scan them for keywords.