document statistics signaling

Nice to know without reading source code or somehow guessing similarity to
ping.

diff --git a/barcat b/barcat
index fabc9a5d5b8dacd10814d031e812ae78d06f23d5..3eb004e56495a5dbf9afda46ed481db43e493199 100755 (executable)
--- a/barcat
+++ b/barcat
@@ -648,6 +648,10 @@ Unspecified, block fill glyphs U+2581-2588 will be used.
 
 Total statistics after all data.
 
+While processing (possibly a neverending pipe),
+intermediate results are also shown on signal I<SIGINFO> if available (control+t on BSDs)
+or I<SIGQUIT> otherwise (ctrl+\ on linux).
+
 =item -u, --unmodified
 
 Do not reformat values, keeping leading whitespace.