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The Gem Command
6:04The gem command is used to manage your gem installation. In this video, we explore some of the different sub commands of ruby gems.
[SOUND] The Gem command does many
things in addition to installing
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Gems. It can tell you what versions
of the Gem are installed, search for
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Gems, tell you about your environment and
more.
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Let's checkout the Gem command in
a bit more depth now using workspaces.
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Let's go ahead and
see what the Gem command really does.
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We can get a list of all the different
commands inside of the Gem command by
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typing gem help.
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And it will show us
exactly what Ruby Gems is.
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What we need more is gem help commands.
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And that will list all of the different
Gem commands that we have to work with.
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So we type that in, and
we can see that we have
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quite a few different things
that we can do with Ruby Gems.
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Now not all of them are going to apply
to what we're doing in this course.
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We're mainly looking at how to install and
use gems.
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However, if we were creating our own gems,
Ruby Gems command gives us
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a bunch of different options for working
with them, such as build and certify.
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Now the commands that we need to
be cognizant of are gem check,
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cleanup, environment, fetch, install,
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list, outdated, pristine, and uninstall.
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There's also the option to search
gems as well as list gems.
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So I'm gonna clear my screen here.
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And if we want help on a gem command,
we could say gem help and
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then the name of the command.
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Now, we're already kind of
familiar with the install command.
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If we say gem help install, it will show
us different options for installation.
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Now we can see there are quite a few
flags that come along with install.
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The most common one that we'll use
is the -v flag which stands for
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installing a specific version of a gem.
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Another option that you'll
use quite a bit is --no
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document If you've been following along
with this outside of work spaces,
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you might have noticed that gems
are being installed with documentation.
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Now the documentation is another
Ruby command that you can use
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to get help with the gem.
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Now, the kind of help that
you'll get by using that,
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is the same thing as looking at
the documentation on a web page.
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For speed, we've disabled the no
document setting in work spaces.
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Now we can also pass around the directory
where binary files are located,
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if that comes with a gem.
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For the most part, we won't be using
many of the different options.
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In the case of a gem which you wanna
install locally, as opposed to remotely.
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You can use -l.
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We didn't need to do that because the gem
was in the same location as we were,
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when we installed it.
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Let's go ahead and
look at the gem environment command.
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This will tell you everything you
need to know about Ruby Gems.
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And if I scroll up here, we can see,
this is our current Ruby Gems environment.
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The version of Ruby Gems we're
using in Workspaces is 2.2.2.
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Our Ruby version is 2.1.5 and
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this shows, where Gems will be installed.
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For the purposes of work spaces,
it's installed into the .local directory.
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Don't be alarmed if this is
different on your computer
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if you're following along
on your own computer.
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And then we can see
the other various options
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That are occurring in our GEM environment.
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Now I'm going to clear my screen here and
type GEM list.
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Now, the Gem list command,
as you could assume from the name,
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lists our installed lists.
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And then, in parentheses,
right after the name of the Gem,
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is the version of the Gem
that's currently installed.
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If we go back, to the Ruby Money Gem,
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we can see that there are other possible
options for versions of this Gem.
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So let's say we wanted to install
version 6.6.0 We coud say gem
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install money and then -v for version.
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And the version number we want to install.
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This would be useful in the case where
an application that you're coding against
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is built using an older
version of the gem.
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And the API might have changed.
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Now we can see that that
version of money was installed.
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So if I clear my screen and
then do gem list once again,
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we can see that two versions
now exist in our list.
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If we had an old version
of an gem installed,
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we could use the update
command to update a gem.
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And we can see that this
updated our rake gem to 10.4.2.
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Now if we list it again, we can see that
that installed the new version of rake,
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and the old one is kept as well.
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We could search for
a gem just like on the Ruby Gems website.
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And we could also install any of
these that we see in the list.
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