Give more information on -l, and note that -U works without -w.

Note that -l, on Windows (i.e., in WinDump), is unbuffered, not
line-buffered, and describe -U as an alternative (that doesn't have that
problem on Windows).

Note that -U does packet-buffering without -w.

Fix up the formatting of the example command lines with -l.

diff --git a/tcpdump.1.in b/tcpdump.1.in
index 3491ba89b5bea918f4d500001cca68b3b6f50bfb..e7d27476a95b2837b3a01961571fa78a879e2ba1 100644 (file)
--- a/tcpdump.1.in
+++ b/tcpdump.1.in
@@ -392,9 +392,37 @@ Make stdout line buffered.
 Useful if you want to see the data
 while capturing it.
 E.g.,
-.br
-``tcpdump\ \ \-l\ \ |\ \ tee dat'' or
-``tcpdump\ \ \-l \ \ > dat\ \ &\ \ tail\ \ \-f\ \ dat''.
+.IP
+.RS
+.RS
+.nf
+\fBtcpdump \-l | tee dat\fP
+.fi
+.RE
+.RE
+.IP
+or
+.IP
+.RS
+.RS
+.nf
+\fBtcpdump \-l > dat & tail \-f dat\fP
+.fi
+.RE
+.RE
+.IP
+Note that on Windows,``line buffered'' means ``unbuffered'', so that
+WinDump will write each character individually if
+.B \-l
+is specified.
+.IP
+.B \-U
+is similar to
+.B \-l
+in its behavior, but it will cause output to be ``packet-buffered'', so
+that the output is written to stdout at the end of each packet rather
+than at the end of each line; this is buffered on all platforms,
+including Windows.
 .TP
 .B \-L
 List the known data link types for the interface, in the specified mode,
@@ -511,11 +539,20 @@ on each dump line.
 Print undecoded NFS handles.
 .TP
 .B \-U
-Make output saved via the
+If the
+.B \-w
+option is not specified, make the printed packet output
+``packet-buffered''; i.e., as the description of the contents of each
+packet is printed, it will be written to the standard output, rather
+than, when not writing to a terminal, being written only when the output
+buffer fills.
+.IP
+If the
 .B \-w
-option ``packet-buffered''; i.e., as each packet is saved, it will be
-written to the output file, rather than being written only when the
-output buffer fills.
+option is specified, make the saved raw packet output
+``packet-buffered''; i.e., as each packet is saved, it will be written
+to the output file, rather than being written only when the output
+buffer fills.
 .IP
 The
 .B \-U