2 files changed, 37 insertions, 8 deletions

diff --git a/coreutils/Config.in b/coreutils/Config.in
index 4eb3db052..6841ec96d 100644
--- a/coreutils/Config.in
+++ b/coreutils/Config.in
@@ -115,6 +115,18 @@ config CONFIG_DD
           by default) using specific input and output blocksizes,
           while optionally performing conversions on it.
 
+config CONFIG_FEATURE_DD_SIGNAL_HANDLING
+        bool "Enable DD signal handling for status reporting"
+        default y
+        depends on CONFIG_DD
+        help
+          sending a SIGUSR1 signal to a running `dd' process makes it 
+          print to standard error the number of records read and written 
+          so far, then to resume copying.
+
+          $ dd if=/dev/zero of=/dev/null& pid=$! $ kill -USR1 $pid; sleep 1; kill $pid 
+          10899206+0 records in 10899206+0 records out
+
 config CONFIG_DF
         bool "df"
         default n
diff --git a/coreutils/dd.c b/coreutils/dd.c
index ce8bcc6a5..378e212de 100644
--- a/coreutils/dd.c
+++ b/coreutils/dd.c
@@ -15,9 +15,9 @@
 #include <unistd.h>
 #include <string.h>
 #include <fcntl.h>
+#include <signal.h>  // For FEATURE_DD_SIGNAL_HANDLING
 #include "busybox.h"
 
-
 static const struct suffix_mult dd_suffixes[] = {
         { "c", 1 },
         { "w", 2 },
@@ -31,12 +31,20 @@ static const struct suffix_mult dd_suffixes[] = {
         { NULL, 0 }
 };
 
+static size_t out_full;
+static size_t out_part;
+static size_t in_full;
+static size_t in_part;
+
+static void dd_output_status(int cur_signal)
+{
+        fprintf(stderr, "%ld+%ld records in\n%ld+%ld records out\n",
+                        (long)in_full, (long)in_part,
+                        (long)out_full, (long)out_part);
+}
+
 int dd_main(int argc, char **argv)
 {
-        size_t out_full = 0;
-        size_t out_part = 0;
-        size_t in_full = 0;
-        size_t in_part = 0;
         size_t count = -1;
         size_t bs = 512;
         ssize_t n;
@@ -53,6 +61,17 @@ int dd_main(int argc, char **argv)
         const char *outfile = NULL;
         char *buf;
 
+        if (ENABLE_FEATURE_DD_SIGNAL_HANDLING)
+        {
+                struct sigaction sa;
+
+                memset(&sa, 0, sizeof(sa));
+                sa.sa_handler = dd_output_status; 
+                sa.sa_flags = SA_RESTART;
+                sigemptyset(&sa.sa_mask);
+                sigaction(SIGUSR1, &sa, 0); 
+        }
+
         for (i = 1; i < argc; i++) {
                 if (strncmp("bs=", argv[i], 3) == 0)
                         bs = bb_xparse_number(argv[i]+3, dd_suffixes);
@@ -180,9 +199,7 @@ int dd_main(int argc, char **argv)
                 bb_perror_msg_and_die("%s", outfile);
         }
 
-        fprintf(stderr, "%ld+%ld records in\n%ld+%ld records out\n",
-                        (long)in_full, (long)in_part,
-                        (long)out_full, (long)out_part);
+        dd_output_status(0);
 
         return EXIT_SUCCESS;
 }