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1+# Install Instructions
2+
3+The pre-compiled binary for Linux works on a very wide range of distributions.
4+
5+It should be possible to install it by running the following commands in your terminal:
6+
7+```bash
8+# Move to your Desktop so you can see what is going on easier.
9+#
10+cd ~/Desktop/
11+
12+# Download the 0.19.0 binary for Linux.
13+#
14+# +-----------+----------------------+
15+# | FLAG | MEANING |
16+# +-----------+----------------------+
17+# | -L | follow redirects |
18+# | -o elm.gz | name the file elm.gz |
19+# +-----------+----------------------+
20+#
21+curl -L -o elm.gz https://github.com/elm/compiler/releases/download/0.19.1/binary-for-linux-64-bit.gz
22+
23+# There should now be a file named `elm.gz` on your Desktop.
24+#
25+# The downloaded file is compressed to make it faster to download.
26+# This next command decompresses it, replacing `elm.gz` with `elm`.
27+#
28+gunzip elm.gz
29+
30+# There should now be a file named `elm` on your Desktop!
31+#
32+# Every file has "permissions" about whether it can be read, written, or executed.
33+# So before we use this file, we need to mark this file as executable:
34+#
35+chmod +x elm
36+
37+# The `elm` file is now executable. That means running `~/Desktop/elm --help`
38+# should work. Saying `./elm --help` works the same.
39+#
40+# But we want to be able to say `elm --help` without specifying the full file
41+# path every time. We can do this by moving the `elm` binary to one of the
42+# directories listed in your `PATH` environment variable:
43+#
44+sudo mv elm /usr/local/bin/
45+
46+# Now it should be possible to run the `elm` binary just by saying its name!
47+#
48+elm
49+```
50+
51+<br/>
52+
53+## Wait, what is the `PATH` variable?
54+
55+When you run a command like `elm make src/Main.elm`, your computer starts by trying to find an executable file called `elm`.
56+
57+The `PATH` is the list of directories that get searched. You can see these directories by running:
58+
59+```bash
60+echo $PATH
61+```
62+
63+This prints `/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin` on my computer. The directories are separated by a `:` so there are five possibilities listed here.
64+
65+When I run `elm make src/Main.elm`, my terminal starts by searching these five directories for an executable file named `elm`. It finds `/usr/local/bin/elm` and then runs `/usr/local/bin/elm make src/Main.elm` with whatever arguments I gave.
66+
67+So the `PATH` environment variable is a convention that allows you to refer to a specific executable file without knowing exactly where it lives on your computer. This is actually how all "terminal commands" work! Commands like `ls` and `cd` are really executable files that live in directories like `/bin` and `/usr/bin` that happen to be listed in your `PATH` variable.
68+
69+So the point of running `sudo mv elm /usr/local/bin/` is to turn the `elm` binary into a terminal command, allowing us to call it just like `ls` and `cd`.
70+
71+**Note:** Why do we need to use `sudo` for that one command? Imagine if some program was able to add executables named `ls` or `cd` to `/usr/local/bin` that did something tricky and unexpected. That would be a security problem! Many distributions make this scenario less likely by requiring special permissions to modify the `/usr/local/bin/` directory.