(usage): Document the fact that SIGUSR1 makes dd

output its current record counts.  Reported by Jurriaan.

diff --git a/src/dd.c b/src/dd.c
index 9977592014a2690ef19d07c3b9a60ea0b389663b..187764ca9e65a2a73076845e80309509e5aff929 100644 (file)
--- a/src/dd.c
+++ b/src/dd.c
@@ -326,6 +326,17 @@ Each KEYWORD may be:\n\
   noerror   continue after read errors\n\
   sync      pad every input block with NULs to ibs-size; when used\n\
               with block or unblock, pad with spaces rather than NULs\n\
+"), stdout);
+      fputs (_("\
+\n\
+Note that sending a SIGUSR1 signal to a running `dd' process makes it\n\
+print to standard error the number of records read and written so far,\n\
+then to resume copying.\n\
+\n\
+  $ dd if=/dev/zero of=/dev/null& pid=$!\n\
+  $ kill -USR1 $pid; sleep 1; kill $pid\n\
+  10899206+0 records in\n\
+  10899206+0 records out\n\
 "), stdout);
       printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
     }