(R)?ex the friendly automation framework



Happy 10th birthday, Rex!

The Rex-1.13.1 release is now available on CPAN. It is focusing on CMDB bugfixes and documentation, while also fixing a missing feature flag. Upgrade is recommended for all users.


The Rex-1.13.0 release is now available on CPAN. It adds on_no_change hooks for file management commands to trigger further actions when files are left unchanged. Upgrade is recommended for all users.


The Rex-1.12.2 release is now available on CPAN. It fixes various regressions, as well as bugs around file management. Upgrade is highly recommended for all users.


The Rex-1.12.1 release is now available on CPAN. It adds documentation for feature flags, and fixes a release packaging issue.


The Rex-1.12.0 release is now available on CPAN. It adds support for local rsync operations, improves tab completion for Bash and Zsh, and fixes related bugs. It also discontinues support for running Rex on Windows 7, Windows Server 2008 R2, and older versions since both mainstream and extended support has already ended for these products.



Need Help?

Rex is a pure open source project, you can find community support in the following places:

Professional support is also available.

» Home » Docs » FAQ


Here we will maintain a list of frequently asked questions with their answers.

Is it called (R)?ex or Rex?

Rex stands for Remote execution. Since automating tasks locally are just as fine as doing the same remotely, (R)?ex is simply a stylized form of (Remote)? execution. Both refers to the same thing: the friendly automation framework.

Why does the run command not format the output?

The run command - called in array context - will return an array.

If you want to print the output to your terminal you have to call it in a scalar context.

my $output = run "df -h";
say $output;

How can I get the current server from within a task?

my $current_server = connection->server;

How can I pass parameters to a task?

task 'mytask', sub {
    my $parameters       = shift;
    my $parameter1_value = $parameters->{parameter1};
    my $parameter2_value = $parameters->{parameter2};

Then you can run mytask from CLI like this:

rex -H hostname mytask --parameter1=value1 --parameter2=value2

Or from Rex code either using run_task:

run_task 'my_task',
  params => { parameter1 => 'value1', parameter2 => 'value2' };

or calling the task as a function:

mytask( { parameter1 => 'value1', parameter2 => 'value2' } );

How can I run a block of code with one command?

One way to do it is to upload your script to the remote, and execute it there. You can use the Rex::Misc::ShellBlock module for that. After copying it into one of the Perl include directories, or into ./lib of your Rex project, you can run your shell code remotely as:

use Rex::Misc::ShellBlock;

task "myexec", sub {
    shell_block <<EOF;
    echo "hi"

See the included documentation of the module about how to use it to run code written in Perl, Python, or other languages.

How can I run a local script on the remote?

If you have a local script 'files/script', you can run it on the remote using the ShellBlock module referred to in the FAQ above. After you install as pointed out above, you can run the script remotely with the command:

use Rex::Misc::ShellBlock;
task "myexec", sub {
    shell_block template('files/script');

How do I run a local script on the remote under a different user?

Given the same scenario as above, but with the additional requirement to run the script as a different user, the solution looks like below:

use Rex::Misc::ShellBlock;
task "myexec", sub {
    sudo {
        command => sub {
            shell_block template('files/script');
        user => 'root'

How do I check the exit status of a remotely run command?

Rex assigns the exit code from the remote invocation of run or shell_block statements to the $? variable.

How do I use Rex's built-in logger for ERROR/WARN/INFO/DEBUG messages?

Rex::Logger::info("some message");            # for INFO  (green)
Rex::Logger::info( "some message", "warn" );  # for WARN  (yellow)
Rex::Logger::info( "some message", "error" ); # for ERROR (red)

How do I load all my custom modules easily?

There are plenty of CPAN modules providing this kind of functionality. For a comprehensive list and overview from some time ago, please read Neil Bowers' article about CPAN modules that (can) load other modules.

Since Rex is just Perl, simply use one of them, like Module::Find or Module::Pluggable.

This might affect when modules are loaded (e.g. at compilation time or at runtime), and/or in which order the modules are loaded. If you run into any troubles because of this, please make sure to specify the dependencies of the custom modules correctly.

How do I indicate the task failed to run properly?

Overall, the same way as in Perl. For example, raising an exception with die() in the task body will abort the task, and calling exit() will bail out from the whole rex process currently running.

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