gem:tldr:8369f

The command is used to install a gem (a Ruby package) with a specific version constraint.

Here's a breakdown of the command:

• gem install: This is the command to install a gem using RubyGems, the package manager for Ruby.
• ${gemname}: This is a placeholder for the name of the gem you want to install. You need to replace ${gemname} with the actual name of the gem you want to install.
• --version: This flag is used to specify a version constraint for the gem installation.
• '~> ${1-0}': This is the version constraint for the gem installation. The ~> symbol means "approximately greater than or equal to" and is commonly used to specify a range of compatible versions. ${1-0} is a shell parameter expansion and it means that if the value 1 is not set, it will default to 0. So, this version constraint would match any version in the 1.x.x range.

To use this command, you need to replace ${gemname} with the name of the gem you want to install. For example, if you want to install the gem called "mygem" with a version constraint of ~> 1.0, the command would be:

gem install mygem --version '~> 1.0'