I don't know how people learn the Bourne shell these days, but when Ilearned it, I first encountered ' : ' as a vaguely peculiar second wayof writing comments, one used by some old shell scripts that hung aroundour systems. This is true as far as it goes, which is not necessarilyvery far.

The difference between # and : is that # starts a real commentthat runs to the end of the line, while : is a real command thatjust does nothing (this is

OpenSSH has decent basic support for opportunistic connection sharing , but most of this is that ssh will look for anexisting master connection before making a new one. It could do betterand enable a true opportunistic connection sharing mode.

There's two problems with ssh's current support for this, one big andone small. First, being the master connection can keep your ssh running when it would otherwise exit. Second, the master connectionexits immediately when there's no active sessions running over it;there'

Following on the basic overview , here's how Iuse OpenSSH's connection sharing feature.

First, since I hate programs that don't exit when I want them to, Idon't let ssh automatically create connection masters. Instead Ialways explicitly create them myself, so that I can do so in a way thatharmlessly parks them in the background. So while I set a ControlPath (to a value mentioned in the previous entry ),I leave ControlMaster set to no , the default.

When