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Posted by jammer on March 27, 2008, 3:35 pm
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>
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> > > I am trying to write a script that takes a list of hosts and sshs into
> > > the first one and then can ssh to other ones. I can only ssh to the
> > > other hosts from the first host.
>
> > > Here is what I tried:
> > > I think it is waiting for the ssh to the first host to finish.
>
> > > I guess I could scp a partial hostlist and a program to *.domain and
> > > then run the program remotely.
> > > Am I on a right track?
>
> > No. Step back a minute and consider how you would do this without Perl:
> > what you want to end up running is
>
> > ssh host1.domain ssh host2 uname -a
>
> > assuming ssh is in your default PATH on host1.domain. What you actually
> > end up running, here (or would if it weren't commented),
>
> > > # print `ssh $line`;
>
> > is
>
> > ssh host1.domain
>
> > with no command specified. This will give you a shell; while it would be
> > possible to remote-control that shell, it's much easier to use ssh's
> > ability to run a command directly. You want something like
>
> > open my $HOSTLIST, '<', 'hostlist3.txt'
> > or die "can't open hostlist3.txt: $!";
>
> > $/ = ''; # this will read a paragraph at a time
> > $\ = "\n"; # avoids needing to print it all the time
>
> > while (<$HOSTLIST>) {
> > my $cmd = join ' ', map "ssh $_", split /\n/;
> > $cmd .= ' uname -a';
> > print "executing '$cmd'";
> > print `$cmd`;
> > }
>
> > which will cope with any number of intervening hosts automatically. Note
> > that this assumes none of the items in hostlist3.txt have spaces in:
> > annoyingly, there isn't a form of backticks corresponding to system
> > LIST, so that would be rather harder to deal with.
>
> > Ben
>
> Here is my next attempt:
>
> #!/bin/perl
>
> use strict;
>
> my $inputFile = 'hostlist3.txt';
>
> open my $HOSTLIST, '<', $inputFile
> or die "can't open hostlist: $!";
>
> $/ = ''; # this will read a paragraph at a time
> $\ = "\n"; # avoids needing to print it all the time
>
> while (<$HOSTLIST>) {
> my @hostList = split /\n/;
>
> my $adminHost = shift( @hostList ); # first line
>
> print 'adminHost=' . $adminHost;
>
> my $otherHosts = join ' ', map "ssh $_ uname -a", @hostList;
>
> my $cmd = "ssh ccn\@$adminHost $otherHosts";
>
> print "executing '$cmd'";
> print `$cmd`;
>
> }
>
> The problem is that I can't seem to run more than one command from
> ssh.
> I don't really want to open and ssh connection for each otherHosts.
>
> What if hostlist3.txt is:
> host1.domain
> host2
> host3
>
> host4.domain
> ...
>
> I need 'ssh host1.domain ssh host2 uname -a ssh host3 uname -a'.
> I can do 'ssh host1.domain ssh host2 uname -a' and 'ssh host1.domain
> ssh host3 uname -a' but I'd rather not ssh to host1.domain more than
> once.
That is a good basis.
I am using that plus copying a script over.
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