Add an example of using multiple threads for DNS lookups.

[hath.git] / doc / man1 / hath.1

diff --git a/doc/man1/hath.1 b/doc/man1/hath.1
index 6bb5ae4236e92f03bc00d1c1dae7c3b495352456..6e7a618c61adbaaf7ac2cf9ccd0abb85dec56264 100644 (file)
--- a/doc/man1/hath.1
+++ b/doc/man1/hath.1
@@ -102,13 +102,26 @@ Perform reverse DNS (PTR) lookups on the IP addresses contained within
 the given CIDRs.
 .P
 .nf
-.I $ hath reversed <<< \(dq198.41.0.4\/30\(dq
+.I $ hath reversed <<< \(dq198.41.0.4/30\(dq
 198.41.0.4: a.root-servers.net.
 198.41.0.5:
 198.41.0.6: rs.internic.net.
 198.41.0.7:
 .fi
 .P
+The DNS lookups are usually the bottleneck for this mode, but we can
+perform them in parallel. Simply pass the number of threads to the GHC
+runtime on the command line; for example, the following will perform
+25 lookups in parallel:
+.P
+.nf
+.I $ hath reversed +RTS -N25 <<< \(dq198.41.0.4/24\(dq
+198.41.0.4: a.root-servers.net.
+198.41.0.5:
+198.41.0.6: rs.internic.net.
+\(pc\(pc\(pc
+.fi
+.P
 Each of the modes also supports a present-tense flavor; the following
 are equivalent to their counterparts: \fBregex\fR, \fBreduce\fR,
 \fBdupe\fR, \fBdiff\fR, \fBlist\fR, \fBreverse\fR.