Hello World: Red Hat Software Collections

Introduction and Prerequisites

In this tutorial, you will set your system up to install software from Red Hat Software Collections (RHSCL), which provides the latest development technologies for Red Hat Enterprise Linux. Then, you will install Node.js v10 and run a simple “Hello, World” application. The whole tutorial should take less than 10 minutes to complete.

Before you begin, you will need a current Red Hat Enterprise Linux 7 server or workstation subscription that allows you to download software and get updates from Red Hat. Developers can get a no-cost Red Hat Enterprise Linux Developer Suite subscription for development purposes by registering and downloading through developers.redhat.com.

If you need help, see Troubleshooting and FAQ.

1. Enable Node.js Red Hat Software Collection (2 minutes)

In this step you will configure your system to obtain software, including the latest dynamic languages, from the RHSCL software repository. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).

Note for RHEL 6 users: If your system uses Red Hat Network (RHN) Classic instead of Red Hat Subscription Management (RHSM) for managing subscriptions and entitlements, please skip this step and follow the Installation chapter of the Red Hat Software Collections Release Notes. The instructions in this section are only for systems using RHSM. The remainder of this tutorial applies to systems running either RHSM or RHN Classic.

Using the Red Hat Subscription Manager GUI

Start Red Hat Subscription Manager using the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.

1. Select Repositories from the System menu of the subscription manager.
2. In the list of repositories, check the Enabled column for rhel-server-rhscl-7-rpms and rhel-7-server-optional-rpms (or rhel-server-rhscl-6-rpms and rhel-6-server-optional-rpms). If you are using a workstation version of Red Hat Enterprise Linux, the repositories will be named rhel-workstation-rhscl-7-rpms and rhel-7-workstation-optional-rpms (or rhel-desktop-rhscl-6-rpms and rhel-6-desktop-optional-rpms). Note: After clicking, it might take several seconds for the check mark to appear in the enabled column.

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

Using subscription-manager from the command line

You can add or remove software repositories from the command line using the subscription-manager tool as the root user. Use the --list option to view the available software repositories and verify that you have access to RHSCL:

$ su -
# subscription-manager repos --list | egrep rhscl

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

If you are using a workstation edition of Red Hat Enterprise Linux, change -server- to -workstation- in the following commands:

# subscription-manager repos --enable rhel-server-rhscl-7-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpms

or for RHEL 6:

# subscription-manager repos --enable rhel-server-rhscl-6-rpms
# subscription-manager repos --enable rhel-6-server-optional-rpms

2. Set up your Node.js development environment (2 minutes)

Next step, install Node.js v10 from RHSCL:

$ su -
# yum install rh-nodejs10

Note: As of Node.js v8, the JavaScript v8 runtime is built in. A separate package is no longer required.

3. Hello World and your first Node.js application (2 minutes)

Under your normal user ID, start a Terminal window. First, use scl enable to add Node.js v4 to your environment, then run Node.js to check the version.

$ scl enable rh-nodejs10 bash
$ node --version
v10.0.0

The next step is to create a Node.js program that can be run from the command line. Using a text editor such as vi, nano, or geditcreate a file named hello.js with the following content:

hello.js

console.log("Hello, Red Hat Developer Program World from Node " + process.version)

Save it and exit the editor. Run it with the node command:

$ node ./hello.js
Hello, Red Hat Developer Program World from Node v10.0.0

If you get the error: node command not found, you need to run scl enable rh-nodejs10 bash first.

The next step is to try a slightly larger Node.js example that implements a tiny web server. Using your preferred text editor, create a file named hello-http.js with the following content:

hello-http.js

var http = require('http');
var port = 8000;
var laddr = '0.0.0.0';
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello, Red Hat Developer Program World from ' +
	    process.version + '!\n');
    console.log('Processed request for '+ req.url);
}).listen(port, laddr);
console.log('Server running at http://' + laddr + ':' + port + '/');

Save it and exit the editor. Run it with the node command:

$ node ./hello-http.js

Now use curl, or a browser such as Firefox, to connect to the Node.js web server http://localhost:8000/:

$ curl http://localhost:8000/
Hello, Red Hat Developer Program World from v10.0.0!

Working with RHSCL packages

The software packages in RHSCL are designed to allow multiple versions of software to be installed concurrently. To accomplish this, the desired package is added to your runtime environment as needed with the scl enable command. When scl enable runs, it modifies environment variables and then runs the specified command. The environmental changes only affect the command that is run by scl and any processes that are run from that command. The steps in this tutorial run the command bash to start a new interactive shell to work in the updated environment. The changes aren’t permanent. Typing exit will return to the original shell with the original environment. Each time you login, or start a new terminal session, scl enable needs to be run again.

While it is possible to change the system profile to make RHSCL packages part of the system’s global environment, this is not recommended. Doing this can cause conflicts and unexpected problems with other applications because the system version of the package is obscured by having the RHSCL version in the path first.

Permanently enable RHSCL in your development environment

To make one or more RHSCL packages a permanent part of your development environment, you can add it to the login script for your specific user ID. this is the recommend approach for development as only processes run under your user ID will be affected.

Using your preferred text editor, add the following line to your ~/.bashrc:

~/.bashrc

# Add Node.js v10 from RHSCL to my login environment
source scl_source enable rh-nodejs10

After making the change, you should log out and log back in again.

When you deliver an application that uses RHSCL packages, a best practice is to have your startup script handle the scl enable step for your application. You should not ask your users to change their environment as this is likely to create conflicts with other applications.

Where to go next?

Learn Node.js and JavaScript using NodeSchool.io tutorials

Now that you have Node.js installed, use the tutorials from nodeschool.io to learn Node.js and JavaScript. You need to have already run scl enable rh-nodejs10 bash or have added Node.js permanently to your development environment.

Install the JavaScript and Node.js tutorials into your current directory:

$ npm install javascripting
$ npm install learnyounode

Temporarily add node_modules/.bin to your PATH:

$ export PATH=$PATH:$PWD/node_modules/.bin

Run the JavaScript tutorial:

$ javascripting

Run the Node.js tutorial:

$ learnyounode

View documentation on the Nodejs.org web site
http://nodejs.org/documentation/

Find additional Node.js packages in RHSCL

$ yum list available rh-nodejs10-\*

View the full list of packages available in RHSCL

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-7-rpms" list available

or for RHEL 6:

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-6-rpms" list available

Introduction and Prerequisites

In this tutorial, you will set your system up to install software from Red Hat Software Collections (RHSCL), which provides the latest development technologies for Red Hat Enterprise Linux. Then, you will install Perl 5.26 and run a simple “Hello, World” application. The whole tutorial should take less than 10 minutes to complete.

Before you begin, you will need a current Red Hat Enterprise Linux 7 server or workstation subscription that allows you to download software and get updates from Red Hat. Developers can get a no-cost Red Hat Enterprise Linux Developer Suite subscription for development purposes by registering and downloading through developers.redhat.com.

If you need help, see Troubleshooting and FAQ.

1. Enable Perl Red Hat Software Collection (2 minutes)

In this step you will configure your system to obtain software, including the latest dynamic languages, from the RHSCL software repository. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).

Note for RHEL 6 users: If your system uses Red Hat Network (RHN) Classic instead of Red Hat Subscription Management (RHSM) for managing subscriptions and entitlements, please skip this step and follow the Installation chapter of the Red Hat Software Collections Release Notes. The instructions in this section are only for systems using RHSM. The remainder of this tutorial applies to systems running either RHSM or RHN Classic.

Using the Red Hat Subscription Manager GUI

Start Red Hat Subscription Manager using the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.

1. Select Repositories from the System menu of the subscription manager.
2. In the list of repositories, check the Enabled column for rhel-server-rhscl-7-rpms and rhel-7-server-optional-rpms (or rhel-server-rhscl-6-rpms and rhel-6-server-optional-rpms). If you are using a workstation version of Red Hat Enterprise Linux, the repositories will be named rhel-workstation-rhscl-7-rpms and rhel-7-workstation-optional-rpms (or rhel-desktop-rhscl-6-rpms and rhel-6-desktop-optional-rpms). Note: After clicking, it might take several seconds for the check mark to appear in the enabled column.

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

Using subscription-manager from the command line

You can add or remove software repositories from the command line using the subscription-manager tool as the root user. Use the --list option to view the available software repositories and verify that you have access to RHSCL:

$ su -
# subscription-manager repos --list | egrep rhscl

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

If you are using a workstation edition of Red Hat Enterprise Linux, change -server- to -workstation- in the following commands:

# subscription-manager repos --enable rhel-server-rhscl-7-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpms

or for RHEL 6:

# subscription-manager repos --enable rhel-server-rhscl-6-rpms
# subscription-manager repos --enable rhel-6-server-optional-rpms

2. Set up your Perl development environment (2 minutes)

Next step, install Perl 5.26 from RHSCL:

$ su -
# yum install rh-perl526

3. Your first Perl Hello World application (2 minutes)

Under your normal user ID, start a Terminal window. First, use scl enable to add Perl 5.26 to your environment, then run Perl to see the version number:

$ scl enable rh-perl526 bash
$ perl -v
This is perl 5, version 20, subversion 1 (v5.26.0)

The next step is to create a Perl program that can be run from the command line. Using a text editor such as vi, nano, or gedit create a file named hello.pl with the following content:

hello.pl

#!/usr/bin/env perl
#
print "Hello, Red Hat Developer Program World from Perl $^V\n";

Save it and exit the editor. Then make the script executable and run it:

$ chmod +x hello.pl
$ ./hello.pl
Hello, Red Hat Developer Program World from Perl v5.26.0

If you get the error: perl command not found, or see a different version number, you need to run scl enable rh-perl526 bash first.

Working with RHSCL packages

The software packages in RHSCL are designed to allow multiple versions of software to be installed concurrently. To accomplish this, the desired package is added to your runtime environment as needed with the scl enable command. When scl enable runs, it modifies environment variables and then runs the specified command. The environmental changes only affect the command that is run by scl and any processes that are run from that command. The steps in this tutorial run the command bash to start a new interactive shell to work in the updated environment. The changes aren’t permanent. Typing exit will return to the original shell with the original environment. Each time you login, or start a new terminal session, scl enable needs to be run again.

While it is possible to change the system profile to make RHSCL packages part of the system’s global environment, this is not recommended. Doing this can cause conflicts and unexpected problems with other applications because the system version of the package is obscured by having the RHSCL version in the path first.

Permanently enable RHSCL in your development environment

To make one or more RHSCL packages a permanent part of your development environment, you can add it to the login script for your specific user ID. this is the recommend approach for development as only processes run under your user ID will be affected.

Using your preferred text editor, add the following line to your ~/.bashrc:

~/.bashrc

# Add Perl 5.26 from RHSCL to my login environment
source scl_source enable rh-perl526

After making the change, you should log out and log back in again.

When you deliver an application that uses RHSCL packages, a best practice is to have your startup script handle the scl enable step for your application. You should not ask your users to change their environment as this is likely to create conflicts with other applications.

Where to go next?

Read Perl Tutorials at learn.perl.org
http://learn.perl.org/tutorials/

Find additional Perl packages in RHSCL

$ yum list available rh-perl526-\*

View the full list of packages available in RHSCL

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-7-rpms" list available

or for RHEL 6:

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-6-rpms" list available

Introduction and Prerequisites

In this tutorial, you will set your system up to install software from Red Hat Software Collections (RHSCL), which provides the latest development technologies for Red Hat Enterprise Linux. Then, you will install PHP 7.2 and run a simple “Hello, World” application. The whole tutorial should take less than 10 minutes to complete.

Before you begin, you will need a current Red Hat Enterprise Linux 7 server or workstation subscription that allows you to download software and get updates from Red Hat. Developers can get a no-cost Red Hat Enterprise Linux Developer Suite subscription for development purposes by registering and downloading through developers.redhat.com.

If you need help, see Troubleshooting and FAQ.

1. Enable PHP Red Hat Software Collections (2 minutes)

In this step you will configure your system to obtain software, including the latest dynamic languages, from the RHSCL software repository. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).

Note for RHEL 6 users: If your system uses Red Hat Network (RHN) Classic instead of Red Hat Subscription Management (RHSM) for managing subscriptions and entitlements, please skip this step and follow the Installation chapter of the Red Hat Software Collections Release Notes. The instructions in this section are only for systems using RHSM. The remainder of this tutorial applies to systems running either RHSM or RHN Classic.

Using the Red Hat Subscription Manager GUI

Start Red Hat Subscription Manager using the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.

1. Select Repositories from the System menu of the subscription manager.
2. In the list of repositories, check the Enabled column for rhel-server-rhscl-7-rpms and rhel-7-server-optional-rpms (or rhel-server-rhscl-6-rpms and rhel-6-server-optional-rpms). If you are using a workstation version of Red Hat Enterprise Linux, the repositories will be named rhel-workstation-rhscl-7-rpms and rhel-7-workstation-optional-rpms (or rhel-desktop-rhscl-6-rpms and rhel-6-desktop-optional-rpms). Note: After clicking, it might take several seconds for the check mark to appear in the enabled column.

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

Using subscription-manager from the command line

You can add or remove software repositories from the command line using the subscription-manager tool as the root user. Use the --list option to view the available software repositories and verify that you have access to RHSCL:

$ su -
# subscription-manager repos --list | egrep rhscl

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

If you are using a workstation edition of Red Hat Enterprise Linux, change -server- to -workstation- in the following commands:

# subscription-manager repos --enable rhel-server-rhscl-7-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpms

2. Set up your PHP development environment (2 minutes)  

Next step, install PHP 7.2 from RHSCL:

$ su -
# yum install rh-php72

3. Hello World and your first application (2 minutes)  

Under your normal user ID, start a Terminal window. Run PHP in interactive mode using scl enable to see the version number:

$ scl enable rh-php72 -- php -a
Interactive shell
php > printf("Hello, Red Hat Developer Program World from PHP %s\n",PHP_VERSION);
Hello, Red Hat Developer Program World from PHP
php > quit
$

The next step is to create a PHP program that can be run from the command line. Using a text editor such as vi, nano, or gedit create a file named hello.php with the following content:

hello.php

#!/usr/bin/scl enable rh-php72 -- php
<?php
print "Hello, Red Hat Developer Program World from PHP " . PHP_VERSION . "\n";
?>

Save it and exit the editor. Then make the script executable and run it:

$ chmod +x hello.php
$ ./hello.php
Hello, Red Hat Developer Program World from PHP 7.2.0

If you get the error “Unable to get file status /etc/scl/conf/rh-php72”, ensure you run “yum update scl-utils” first to get the latest version of the scl-utils package.

Working with RHSCL packages

The software packages in RHSCL are designed to allow multiple versions of software to be installed concurrently. To accomplish this, the desired package is added to your runtime environment as needed with the scl enable command. When scl enable runs, it modifies environment variables and then runs the specified command. The environmental changes only affect the command that is run by scl and any processes that are run from that command. The steps in this tutorial run the command bash to start a new interactive shell to work in the updated environment. The changes aren’t permanent. Typing exit will return to the original shell with the original environment. Each time you login, or start a new terminal session, scl enable needs to be run again.

While it is possible to change the system profile to make RHSCL packages part of the system’s global environment, this is not recommended. Doing this can cause conflicts and unexpected problems with other applications because the system version of the package is obscured by having the RHSCL version in the path first.

Permanently enable RHSCL in your development environment

To make one or more RHSCL packages a permanent part of your development environment, you can add it to the login script for your specific user ID. this is the recommend approach for development as only processes run under your user ID will be affected.

Using your preferred text editor, add the following line to your ~/.bashrc:

~/.bashrc

# Add PHP 7.2 from RHSCL to my login environment
source scl_source enable rh-php72

After making the change, you should log out and log back in again.

When you deliver an application that uses RHSCL packages, a best practice is to have your startup script handle the scl enable step for your application. You should not ask your users to change their environment as this is likely to create conflicts with other applications.

Where to go next?

PHP Tutorial at php.net
http://php.net/manual/en/tutorial.php

Find additional PHP packages in RHSCL

$ yum list available rh-php72\*

View the full list of packages available in RHSCL

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-7-rpms" list available

Or for RHEL 6:

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-6-rpms" list available

Introduction and Prerequisites

In this tutorial, you will set your system up to install software from Red Hat Software Collections (RHSCL), which provides the latest development technologies for Red Hat Enterprise Linux. Then, you will install Python 3.6 and run a simple “Hello, World” application. The whole tutorial should take less than 10 minutes to complete.

Before you begin, you will need a current Red Hat Enterprise Linux 7 server or workstation subscription that allows you to download software and get updates from Red Hat. Developers can get a no-cost Red Hat Enterprise Linux Developer Suite subscription for development purposes by registering and downloading through developers.redhat.com.

If you need help, see Troubleshooting and FAQ.

1. Enable Python Red Hat Software Collections (2 minutes)

In this step you will configure your system to obtain software, including the latest dynamic languages, from the RHSCL software repository. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).

Note for RHEL 6 users: If your system uses Red Hat Network (RHN) Classic instead of Red Hat Subscription Management (RHSM) for managing subscriptions and entitlements, please skip this step and follow the Installation chapter of the Red Hat Software Collections Release Notes. The instructions in this section are only for systems using RHSM. The remainder of this tutorial applies to systems running either RHSM or RHN Classic.

Using the Red Hat Subscription Manager GUI

Start Red Hat Subscription Manager using the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.

1. Select Repositories from the System menu of the subscription manager.
2. In the list of repositories, check the Enabled column for rhel-server-rhscl-7-rpms and rhel-7-server-optional-rpms (or rhel-server-rhscl-6-rpms and rhel-6-server-optional-rpms). If you are using a workstation version of Red Hat Enterprise Linux, the repositories will be named rhel-workstation-rhscl-7-rpms and rhel-7-workstation-optional-rpms (or rhel-desktop-rhscl-6-rpms and rhel-6-desktop-optional-rpms). Note: After clicking, it might take several seconds for the check mark to appear in the enabled column.

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

Using subscription-manager from the command line

You can add or remove software repositories from the command line using the subscription-manager tool as the root user. Use the --list option to view the available software repositories and verify that you have access to RHSCL:

$ su -
# subscription-manager repos --list | egrep rhscl

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

If you are using a workstation edition of Red Hat Enterprise Linux, change -server- to -workstation- in the following commands:

# subscription-manager repos --enable rhel-server-rhscl-7-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpms

Or for RHEL 6:

# subscription-manager repos --enable rhel-server-rhscl-6-rpms
# subscription-manager repos --enable rhel-6-server-optional-rpms

2. Set up your Python development environment (2 minutes)

Next step, install Python 3.6 from RHSCL:

$ su -
# yum install rh-python36

3. Hello World and your first Python application (2 minutes)

Under your normal user ID, start a Terminal window. Run Python in interactive mode using scl enable to see the version number:

$ scl enable rh-python36 bash
$ python3
Python 3.6.3 (default, Oct  5 2017, 20:27:50)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, Red Hat Developer Program World")
Hello, Red Hat Developer Program World
>>> quit()
$

The next step is to create a Python program that can be run from the command line. Using a text editor such as vi, nano, or geditcreate a file named hello.py with the following content:

hello.py

import sys
version = "Python %d.%d" % (sys.version_info.major, sys.version_info.minor)
print("Hello, Red Hat Developer Program World from",version)

Save it and exit the editor. Then make the script executable and run it:

$ chmod +x hello.py
$ ./hello.py
Hello, Red Hat Developer Program World from Python 3.6

If you get the error “Unable to get file status /etc/scl/conf/rh-python36”, ensure you run “yum update scl-utils” first to get the latest version of the scl-utils package.

Working with RHSCL packages

The software packages in RHSCL are designed to allow multiple versions of software to be installed concurrently. To accomplish this, the desired package is added to your runtime environment as needed with the scl enable command. When scl enable runs, it modifies environment variables and then runs the specified command. The environmental changes only affect the command that is run by scl and any processes that are run from that command. The steps in this tutorial run the command bash to start a new interactive shell to work in the updated environment. The changes aren’t permanent. Typing exit will return to the original shell with the original environment. Each time you login, or start a new terminal session, scl enable needs to be run again.

While it is possible to change the system profile to make RHSCL packages part of the system’s global environment, this is not recommended. Doing this can cause conflicts and unexpected problems with other applications because the system version of the package is obscured by having the RHSCL version in the path first.

Permanently enable RHSCL in your development environment

To make one or more RHSCL packages a permanent part of your development environment, you can add it to the login script for your specific user ID. this is the recommend approach for development as only processes run under your user ID will be affected.

Using your preferred text editor, add the following line to your ~/.bashrc:

~/.bashrc

# Add Python 3.6 from RHSCL to my login environment
source scl_source enable rh-python36

After making the change, you should log out and log back in again.

When you deliver an application that uses RHSCL packages, a best practice is to have your startup script handle the scl enable step for your application. You should not ask your users to change their environment as this is likely to create conflicts with other applications.

Where to go next?

Python 3 Tutorial at Python.org
https://docs.python.org/3/tutorial/

Find additional Python packages in RHSCL

$ yum list available rh-python36-\*

View the full list of packages available in RHSCL

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-7-rpms" list available

Or for RHEL 6:

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-6-rpms" list available

Introduction and Prerequisites

In this tutorial, you will set your system up to install software from Red Hat Software Collections (RHSCL), which provides the latest development technologies for Red Hat Enterprise Linux. Then, you will install Ruby 2.6 and run a simple “Hello, World” application. The whole tutorial should take less than 10 minutes to complete.

Before you begin, you will need a current Red Hat Enterprise Linux 7 server or workstation subscription that allows you to download software and get updates from Red Hat. Developers can get a no-cost Red Hat Enterprise Linux Developer Suite subscription for development purposes by registering and downloading through developers.redhat.com.

If you need help, see Troubleshooting and FAQ.

1. Enable Ruby Red Hat Software Collections (2 minutes)

In this step you will configure your system to obtain software, including the latest dynamic languages, from the RHSCL software repository. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).

Note for RHEL 6 users: If your system uses Red Hat Network (RHN) Classic instead of Red Hat Subscription Management (RHSM) for managing subscriptions and entitlements, please skip this step and follow the Installation chapter of the Red Hat Software Collections Release Notes. The instructions in this section are only for systems using RHSM. The remainder of this tutorial applies to systems running either RHSM or RHN Classic.

Using the Red Hat Subscription Manager GUI

Start Red Hat Subscription Manager using the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.

1. Select Repositories from the System menu of the subscription manager.
2. In the list of repositories, check the Enabled column for rhel-server-rhscl-7-rpms (rhel-server-rhscl-6-rpms) and rhel-7-server-optional-rpms (rhel-6-server-optional-rpms). If you are using a workstation version of Red Hat Enterprise Linux, the repositories will be named rhel-workstation-rhscl-7-rpms (rhel-workstation-rhscl-6-rpms) and rhel-7-workstation-optional-rpms (rhel-6-workstation-optional-rpms). Note: After clicking, it might take several seconds for the check mark to appear in the enabled column.

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

Using subscription-manager from the command line

You can add or remove software repositories from the command line using the subscription-manager tool as the root user. Use the --list option to view the available software repositories and verify that you have access to RHSCL:

$ su -
# subscription-manager repos --list | egrep rhscl

If you don’t see any RHSCL repositories in the list, your subscription might not include it. See Troubleshooting and FAQ for more information.

If you are using a workstation edition of Red Hat Enterprise Linux, change -server- to -workstation- in the following commands for RHEL 7:

# subscription-manager repos --enable rhel-server-rhscl-7-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpms

or for RHEL 6:

# subscription-manager repos --enable rhel-server-rhscl-6-rpms
# subscription-manager repos --enable rhel-6-server-optional-rpms

2. Set up your development environment (2 minutes)

Next step, install Ruby 2.6 from RHSCL:

$ su -
# yum install rh-ruby26

3. Hello World and your first Ruby application (2 minutes)

Under your normal user ID, start a Terminal window. First, use scl enable to add Ruby 2.6 to your environment, then run Ruby in interactive mode to see the version number:

$ scl enable rh-ruby26 bash
$ irb
irb(main):001:0> puts "Hello, Red Hat Developer Program World from Ruby " + RUBY_VERSION
Hello, Red Hat Developer Program World from Ruby 2.6.0
=> nil
irb(main):002:0> quit

The next step is to create a Ruby program that can be run from the command line. Using a text editor such as vi, nano, or gedit create a file named hello.rb with the following content:

#!/usr/bin/env ruby
#
puts "Hello, Red Hat Developer Program World from Ruby " + RUBY_VERSION

Save it and exit the editor. Then make the script executable and run it:

$ chmod +x hello.rb
$ ./hello.rb
Hello, Red Hat Developer Program World from Ruby 2.6.0

If you get the error: ruby command not found, or see a different version number, you need to run scl enable rh-ruby26 bash first.

Working with RHSCL packages

The software packages in RHSCL are designed to allow multiple versions of software to be installed concurrently. To accomplish this, the desired package is added to your runtime environment as needed with the scl enable command. When scl enable runs, it modifies environment variables and then runs the specified command. The environmental changes only affect the command that is run by scl and any processes that are run from that command. The steps in this tutorial run the command bash to start a new interactive shell to work in the updated environment. The changes aren’t permanent. Typing exit will return to the original shell with the original environment. Each time you login, or start a new terminal session, scl enable needs to be run again.

While it is possible to change the system profile to make RHSCL packages part of the system’s global environment, this is not recommended. Doing this can cause conflicts and unexpected problems with other applications because the system version of the package is obscured by having the RHSCL version in the path first.

Permanently enable RHSCL in your development environment

To make one or more RHSCL packages a permanent part of your development environment, you can add it to the login script for your specific user ID. this is the recommend approach for development as only processes run under your user ID will be affected.

Using your preferred text editor, add the following line to your ~/.bashrc:

~/.bashrc

# Add Ruby 2.6 from RHSCL to my login environment
source scl_source enable rh-ruby26

After making the change, you should log out and log back in again.

When you deliver an application that uses RHSCL packages, a best practice is to have your startup script handle the scl enable step for your application. You should not ask your users to change their environment as this is likely to create conflicts with other applications.

Learn Ruby in 20 Minutes at Ruby-lang.org
https://www.ruby-lang.org/en/documentation/quickstart/

Find additional Ruby packages in RHSCL

$ yum list available rh-ruby26-\*

View the full list of packages available in RHSCL

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-7-rpms" list available

or for RHEL 6:

$ yum --disablerepo="*" --enablerepo="rhel-server-rhscl-6-rpms" list available