Looking to execute a perl script on a remote machine via a Perl script. Appears one option is to use system() function and create an ssh key so the password is not required. Which leads me to the focus of this question, the other option appears to be to install and run one of these perl modules:
Net::SSH
Net::SSH2
Net::OpenSSH
Besides the protocol used, what else should I be comparing with these Perl modules?
The Net::OpenSSH documentation has a section describing the pros and cons of each. Here are some excerpts related to the ones you are asking about, but the documentation lists more:
Net::SSH is just a wrapper around any
SSH binary commands available on the
machine. It can be very slow as they
establish a new SSH connection for
every operation performed.
Net::SSH2 is much better than
Net::SSH::Perl, but not completely
stable yet. It can be very difficult
to install on some specific operative
systems and its API is also limited,
in the same way as Net::SSH::Perl.
Net::OpenSSH has a very perlish
interface. Most operations are
performed in a fashion very similar to
that of the Perl builtins and common
modules (i.e. IPC::Open2).
However, choice of platform may limit your options.
On the other hand, Net::OpenSSH does
not work on Windows, not even under
Cygwin.
Granted, the list is biased towards Net::OpenSSH, but it gives you an idea of the major differences between the modules.
Related
I'm running the tcl(which has expect script) using perl with,
system("C:/Tcl/bin/tclsh86 C:/Users/sysadmin/desktop/expect.tcl");
It's not executing the all commands in the script, but its working fine on ubuntu.
What command should i use to run this completely using perl on Windows?
On Unix Expect works using virtual terminals. By contrast, Expect on Windows uses the debugging subsystem. (There's nothing like virtual terminals on Windows.) This has the down-side that programs that are marked as being impossible to debug (i.e., some system programs, notably including telnet.exe though ftp.exe might also be on that list) cannot be automated by Expect at all. The OS just refuses to let Expect connect to the process.
Is this what is happening to you? I can't tell from the minimal information you've given, but it is by far the most common reason for problems with porting an Expect script between platforms (once you've taken into account mundane things like different paths and programs that just aren't there on all platforms).
The up-side is that both Tcl and Perl are quite capable of talking directly to anything that you'd use telnet or ftp to talk to (as both are entirely proficient at TCP/IP). In fact, both are probably better at doing it natively than anything you'd likely achieve through use of Expect.
Is it possible to run multiple installs of Perl (in "containers") on one machine?
Reason is that I have different Perl-based server side web applications and wish to schedule updates to them independently.
For example, bugzilla upgrades seem to me to be very invasive, downloading all manner or module updates and lengthy, too (thereby increasing the chance of unpredictable behavior on other applications that depend on those modules, during the time that the upgrade is still partial).
I think it should be possible to run multiple independent server-side CGI Perl applications on one server, I'd rather not be told to separate them onto different machines - I think that's wasteful and I don't have that resource anyway.
Investigate PerlBrew and cpanm:
http://qa.celogeek.com/programming/perl/for/developer/overview
Edit, more info:
http://www.bryanesmith.com/documents/a2pm/perlbrew-june-14-2011.pdf
http://www.dagolden.com/index.php/1384/parallel-make-for-perlbrew/
http://www.perlbrew.pl/
It's easy to install and manage multiple perls. Simply install them in different places and use each perl's tools. I talk about this in The Effective Perler.
Some people suggest perlbrew without realizing that it doesn't really give you any benefit. It can download a perl, configure and install it, and switch around symbolic links to make one of those the default. It doesn't do anything magical, though.
Downloading and installing aren't a problem though. You've never needed root or sudo to do that, and if you do, you'll still need it for perlbrew. You can always install into any directory where you have permission. perlbrew doesn't get around that at all. From the source directory, you have two simple commands to run:
$./Configure -des -Dprefix=/where/you/want/to/install
$ make install
For you, that might mean Bugzilla gets its own perl:
$./Configure -des -Dprefix=/where/you/want/to/install/bugzilla-perl
$ make install
From there, you have a completely self-contained perl installation. When it matters to me which perl I use, I give the program the full path to it:
#!/where/you/want/to/install/bugzilla-perl/bin/perl
It's much easier to make these per-applications installations without perlbrew, which wants to do as much as it can for you, including deciding the directory name, which it prefers you didn't know at all.
perlbrew's main advantage is not the compilation and installation, but it's switch feature to let you make one perl the default. You probably don't want that feature though because you want bugzilla, CGI programs, and so on using only the perl you want them to use, not whatever default perl you last specified.
When you want to update the bugzilla-perl, just use it's tools, which already have adjusted shebang lines to find the right perl:
$ /where/you/want/to/install/bugzilla-perl/bin/cpan ...
I don't like all of those long paths, though, which is why I make links to them all. Then I can just call them with whatever naming scheme I decide, which might be:
$ bugzilla-cpan ...
There's never a question about which tool or version I'm using.
I am wanting to create an install script in the fashion of npm's (curl http://example.com/install.sh | sh) but it leaves me asking the question: can I just write the script in perl? As far as I know, perl is installed by default on at least ubuntu, RHEL & OS X - so I'm wondering in the year 2011, can I not write shell and still be generic enough for everyone? Is there a third and better option?
This would be targeting a user's development box, not staging or production.
What I want to do specifically is use this install script to bootstrap a development environment easily without the overhead of creating and maintaining packages. The script would have 4 steps:
check and make sure git is installed
use git to clone a repo to cwd
pull down and save a perl control script to /usr/bin, make it executable
add some environment variables (related post: linux cross-distro environment variable modification via script?)
That's it. My thinking is this is simple and generic enough to use a bootstrap script rather than a package. And my target audience is a user's unix or linux local development system.
The best option is to simply use the existing, well-oiled and -used (development) toolchain for the language the target app is written in. Not doing so frivolously discards the network effects gained from the ecologies that have grown around them.
C: GNU autotools
Haskell: Cabal
Perl: EU::MM, M::B, M::I
etc. etc.
Installing from the Web should be reserved for conveniently bootstrapping a user's system into the development environment.
Do tell more details about your software to get less general advice.
Edit: response to your addendum.
I dissuade you from a Web installer. This isn't bootstrapping an installation tool, this is plain installation of software and it should be done with with e.g. a Module::Build subclass.
I think perl is ubiquitous enough for you to write your installer in it. Shell is a lot more awkward anyway.
You might want to consider actually packaging your application as a deb or rpm or even using makeself rather than providing a raw script.
Here's a list of the various distributions of perl:
https://www.socialtext.net/perl5/distributions
Even if perl doesn't ship on every little obscure distro it's just an apt-get (or whatever) away. You might run into problems due to the various versions of perl installed however.
Use something like:
perl -E "$( wget -q -O - http://host/intall.pl )"
Also you can use
`cmd`
instead of
$(cmd)
but anyway, double-quote your choice.
Being very new to Perl but not to dynamic languages, I'm a bit surprised at how not straight forward the manage of modules is.
Sure, cpan X does theoretically work, but I'm working on the same project from three different machines and OSs (at work, at home, testing in an external environment).
At work (Windows 7) I have problem using cpan because of our firewall that makes ftp unusable
At home (Mac OS X) it does work
In the external environment (Linux CentOs) it worked after hours because I don't have root access and I had to configure cpan to operate as a non-root user
I've tried on another server where I have an access. If the previous external environment is a VPS and so I have a shell access, this other one is a cheap shared hosting where I have no way to install new modules other than the ones pre-installed
At the moment I still can't install Template under Windows. I've seen that as an alternative I could compile it and I've also tried ActiveState's PPM but the module is not existent there.
Now, my perplexity is about Perl being a dynamic language. I've had all these kind of problems while working, for example, with C where I had to compile all the libraries for all the platform, but I thought that with Perl the approach would have been very similar to Python's or PHP's where in 90% of the cases copying the module in a directory and importing it simply works.
So, my question: if Perl's modules are written in Perl, why the copy/paste approach will not work? If some (or some part) of the modules have to be compiled, how to see in CPAN if a module is Perl-only or it relies upon compiled libraries? Isn't there a way to download the module (tar, zip...) and use cpan to deploy it? This would solve my problem under Windows.
Now, Perl is a dynamic language, but that doesn't imply that everything that people write is portable across platforms. That's not the fault of the language. It's not even the fault of the programmer. Some things, like Win32::OLE shouldn't work on Unix. :)
Other dynamic languages will have some of the same problems. If you have to compile C code, you won't be able to merely copy files to another machine. Some distributions configure the code slightly differently depending on your operating system, etc.
Even if you could copy files, you have to ensure that you copy all of the files that you need. Do you know everything that you need for a particular module? Remember, many of them have dependencies.
Most of the problems you're having aren't anything to do with the language. You're having trouble with the tools. If you want a zero conf CPAN tool that makes all the decisions for you, try cpanminus. It's mostly the same thing that you'd get out of cpan (although different code), but it makes all of the decisions for you. It doesn't run any of the distribution tests, and it installs into your user directory. When you need something that gives you control, come back to cpan.
In the external environment (Linux CentOs) it worked after hours because I don't have root access and I had to configure cpan to operate as a non-root user
This is one of those times when it helps to know The Trick. In this case local::lib, which lets you configure a non-root install area and all the ENV variables in about three minutes.
if perl's modules are written in perl, why the copy/past approach will not work?
Some are written in Pure Perl, but many are written partially in C (using Perl's XS API) for efficiency.
Sometimes you end up with situations like JSON::XS, JSON::PP and JSON::Any to autoselect the best one that is installed.
Isn't there a way to download the module (tar, zip...) and use cpan to deploy it?
The cpan program is all about getting things from the Internet. You can download the package (there will be a link along the lines of "Download: CGI.pm-3.49.tar.gz" on the right hand side of the CPAN page), untar it, then
perl Makefile.PL
make
make install
You would probably be better off configuring your cpan installation to use only HTTP sources (in the urllist config option). Possibly going to far as to create a mini CPAN mirror inside your network.
Sometimes I see people use http://codepad.org as a way to quickly run/test their Perl snippets (it supports doing that with a wide variety of languages, from C to Scheme to Perl).
It's pretty obvious that there must be some limitations as to what code/features can be tested with codepad - does anyone know what those limitations are for Perl runner?
I'll get the ball rolling on my own observation: not every CPAN module is available :(
Mostly based on their "about" page:
codepad only supports Perl 5.8.0
Presumably, like any Perl install, not every module (CPAN or otherwise) is present.
As a specific example, List::MoreUtils is missing.
As a sub-limitation, they seem to run on Linux. So any Windows specific modules would certainly be out.
It's in a chroot jail with system calls restrictions. Among other things this seems to prevent file creation (my snippets creating files in a current directory or /tmp both errored out, as well as File::Temp calls)
codepad code is executed on a virtual machine. Behind firewalls. And buried in a bunker. So certain functionality is probably disabled - especially networking/internet one. The exact "about" quote is:
The supervisor processes run on virtual machines, which are firewalled such that they are incapable of making outgoing connections.
The machines that run the virtual machines are also heavily firewalled, and restored from their source images periodically.
It's easier to just run Perl code locally. It's easy to install multiple versions of Perl and to track separate module repositories. It's also not hard to run just about any operating system you want in a virtual machine. Why you'd need anyone's else's service to do what you can do better yourself is beyond me.