[Sussex] Future Talk [Was: Label and partition external hard drive]

[Desmond Armstrong]

  On 26/02/11 10:05, Steve Dobson wrote:
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> Hi Desmond
>
> I've started a new thread for this as we are now well away from the
> original topic.
>
> On 25/02/11 21:03, Desmond Armstrong wrote:
>> I have an idea for you to present.
>> What I think would be very helpful is to choose some fairly small CLI
>> function and then to build perhaps using Python some sort of GUI for
>> it. In this way we can appreciate the build up of these functions.
> Nice idea, but not something I could present as that is not the way I
> work.  I've never used Python, and it is also not the way that you gain
> the power of the CLI.
>
> When Apple produced OSX I jumped for joy!  There were a lot of old CLI
> diehards that where claiming that you could not, no way, not in a
> million years, produce a GUI for *nix administration.  Apple had just
> proved them wrong.
>
> Now a few years later we have a rich set of GUI system admin tasks, at
> least I do in Gnome, and I doubt that there aren't equivalents in KDE.
> I doubt that there is any single task that one can do on the CLI that
> doesn't have a GUI app somewhere.
>
> If you want to do one task then I would say that a good GUI is easier
> (and probably quicker).  I use to use cdrecord to burn my ISO images,
> now I use Brasero.  Even for a CLI hacker like me Brasero is quicker to
> use.  And that it's the only case.  I use RhythmBox now for ripping my
> CDs (ripit is the command line tool I use to use).  The list goes on.
>
> I've said it before but I will say it again: The power of the CLI comes
> from chaining commands together!
>
>> I think this sort of presentation coming from somebody well versed in
>> the CLI such as yourself would be very instructive. It would also be
>> very helpful to those who are not continuously doing CLI and
>> consequently will normally be quite error prone.
> If I were to give a talk it would more likely be on the lines of how to
> approach command line scripting and the power of the pipe!  I would do
> it by example.  Here is an example from the real world.
>
> I was consulting on a warehouse management software installation a few
> years back.  Every so often we needed to take the system over for
> software updates, database fixes and the like.  To do this we first had
> to kick off all the users (packers) out on the warehouse floor.
>
> We would put a message out over the PA, but they just didn't listen.  It
> was a big warehouse, you couldn't find them all and if you killed of
> their client programs (all running on a central super-mini form HP) the
> some of buggers would log back on and by the time you had killed of the
> last one by hand the some would be logged back in.
>
> I did the whole job very fast on the CLI (there was no GUI for HPUX) in
> one line.  The other techies there, some with years of experience of the
> software, had no idea how to kill off the client programs quickly.
>
> "ps" lists the processes running on a *nix system.  On Linux the best
> arguments to use are "-elf" to get the full listing.  Best for human
> reading that is, but for this purpose "-ef" gives me just the info I need.
>
>      $ ps -ef
>
> You get a long list that includes information like the user that the
> process is being run by, time it was started, it's unique processes
> identity (pid) and the pid of its parent process, not to mention the
> process command itself.
>
> We only wanted to kill of one particular process name run by the same
> users. (All the pickers logged on using that same account.)  The best
> command for filtering text information is grep.
>
>     $ ps -ef | grep ^user | grep program
>
> I used two greps.  The first picks out all the command by the fixed user
> ("user" here).  It passes that filtered list to the second grep which
> just picks out those entries that are the command ("program").  But this
> list still isn't really useable yet.  We can do more!
>
> To kill a process you need to pass the pid to the "kill" command.  The
> pid is listed in the second column.  awk is a powerful scripting
> language in it's own right, here I use it to construct the commands to
> kill the programs I wanted:
>
>     $ ps -ef | grep ^user | grep program | awk '{print "kill " $2}'
>
> There are all the kill commands to kill off the program we wanted.  But
> re-typing them in would take an age.
>
> Now one could send those commands to a file make the file executable and
> then execute it but there is a much simpler way.  If you feed a set of
> commands into a CLI shell it will execute them!
>
>     $ ps -ef | grep ^user | grep program | awk '{print "kill " $2}' | sh
>
> There!  A one line script to find a set of processes run by the same
> user account and kill them.  I took me a couple of minutes to build the
> script up, bit by bit more or less as I did above on site live.
>
> Would anyone be interested in a talk like that?

Yes.
A talk along those lines would be very helpful so I shall look forward 
to it.

Thanks Steve, for thinking about this one and for your considered reply, 
it is very constructive and very helpful.