[clug-talk] running a remote process
greg at taord.com
Wed Apr 8 14:51:16 PDT 2009
Thanks all. Turns out Expect was the way to go for me ... actually pexpect
(a pure python implementation). There is a simple little ssh session example
that comes with the module (originally hacked together by none other than
I'm thinking this might be our topic for tomorrow night's python meeting :-)
Thanks a million guys,
2009/4/8 Mark Carlson <carlsonmark at gmail.com>
> On 4/8/09, Mark Carlson <carlsonmark at gmail.com> wrote:
> > On 4/8/09, Greg Saunders <greg at taord.com> wrote:
> > > Hi all, I'm looking for the best way to run a remote process. SSH with
> > > "ssh user at host.domain.com remoteprocess"
> > >
> > > Is there a better way, especially if you have to execute 20 remote
> > > each time and those commands are determined on the fly and not known
> > > of time.
> > >
> > > Thanks!
> > > Greg
> > "best" really depends on your situation...
> > Personally, I find SSH to be the best for me. If you need to use
> > keys, use them, if you don't want to, don't.
> > If you want to execute 20 commands, use a list of commands.
> > Some simple examples:
> > # Commands are executed sequentially:
> > % command1; cmd2; cmd3
> > # Commands are only executed if the previous one returns zero:
> > % command1 && cmd2 && cmd3
> > # Commands are only executed if the previous one returned nonzero
> > % command1 || cmd2 || cmd3
> > A more complex example:
> > # Run command 1, then command 2, and finally command 3 only if command
> > 2 did not return an error
> > % command1; cmd2 && cmd3
> > From the bash man page: http://linux.die.net/man/1/bash
> > ----------------------------------------
> > Shell Grammar
> > <...>
> > Lists
> > A list is a sequence of one or more pipelines separated by one of the
> > operators ;, &, &&, or ||, and optionally terminated by one of ;, &,
> > or <newline>.
> > Of these list operators, && and || have equal precedence, followed by
> > ; and &, which have equal precedence.
> > A sequence of one or more newlines may appear in a list instead of a
> > semicolon to delimit commands.
> > If a command is terminated by the control operator &, the shell
> > executes the command in the background in a subshell. The shell does
> > not wait for the command to finish, and the return status is 0.
> > Commands separated by a ; are executed sequentially; the shell waits
> > for each command to terminate in turn. The return status is the exit
> > status of the last command executed.
> > The control operators && and || denote AND lists and OR lists,
> > respectively. An AND list has the form
> > command1 && command2
> > command2 is executed if, and only if, command1 returns an exit status of
> > An OR list has the form
> > command1 || command2
> > command2 is executed if and only if command1 returns a non-zero exit
> > status. The return status of AND and OR lists is the exit status of
> > the last command executed in the list.
> > -Mark C.
> Oh, and if you don't use quotes to enclose the commands, you may be
> surprised by the results!
> Ex: both commands run on remote machine:
> % ssh 127.0.0.1 "echo hello; echo world"
> Ex: "echo hello" run remotely, "echo world" run locally
> % ssh 127.0.0.1 echo hello; echo world
> The results look the same in this case... but if your commands are
> backing up a computer or something, you will soon notice a difference!
> -Mark C.
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