Update and polish shell code in README (#155)

README.md

@@ -15,18 +15,18 @@ Either install the LLVM packages on your system:
 --------------------------------------------
 
 On macOS, use [pkgsrc](http://pkgsrc.joyent.com/install-on-osx/) and run the following commands:
-```
-    pkgin in llvm clang
+```sh
+    ~$ pkgin in llvm clang
 ```
 
 On CentOS, install the llvm-devel package:
-```
-    dnf install llvm-devel clang
+```sh
+    ~# dnf install llvm-devel clang
 ```
 
 On Debian and derivatives, install the llvm-dev package via:
-```
-    apt install llvm-dev clang
+```sh
+    ~# apt install llvm-dev clang
 ```
 
 Or compile LLVM yourself:
@@ -36,15 +36,15 @@ Note: to convert C to LLVM IR to run the tests, you will also need a C compiler
 The first step is to compile LLVM on your machine
 (this assumes an in-tree build, but out-of-tree will also work):
 
-
-     git clone https://github.com/llvm/llvm-project.git
-     cd llvm-project
-     git checkout release/8.x
-     mkdir llvm/build
-     cd llvm/build
-     cmake ..
-     make
-
+```sh
+     ~$ git clone https://github.com/llvm/llvm-project.git
+     ~$ cd llvm-project
+     llvm-project$ git checkout release/8.x
+     llvm-project$ mkdir llvm/build
+     llvm-project$ cd llvm/build
+     build$ cmake ..
+     build$ make
+```
 To run tests, you need to build `lli`.
 
 
@@ -54,32 +54,32 @@ Step 2: Compiling LLVM-CBE
 Now you can download and compile llvm-cbe.
 
 If you built LLVM yourself, put it in the same folder you built LLVM in:
-
-    cd $HOME/llvm-project/llvm/projects
-    git clone https://github.com/JuliaComputing/llvm-cbe
-    cd ../build
-    cmake -S ..
-    make llvm-cbe
-
+```sh
+    ~$ cd llvm-project/llvm/projects
+    projects$ git clone https://github.com/JuliaComputing/llvm-cbe
+    projects$ cd ../build
+    build$ cmake -S ..
+    build$ make llvm-cbe
+```
 If you used your distribution's package, put it wherever you feel like:
-
-    git clone https://github.com/JuliaComputing/llvm-cbe
-    cd llvm-cbe && mkdir build && cd build
-    cmake -S ..
-    make llvm-cbe
-
+```sh
+    ~$ git clone https://github.com/JuliaComputing/llvm-cbe
+    ~$ cd llvm-cbe && mkdir build && cd build
+    build$ cmake -S ..
+    build$ make llvm-cbe
+```
 Step 3: Usage Examples
 ======================
 
 If llvm-cbe compiles, you should be able to run it with the following commands.
-```
-$ cd $HOME/llvm-project/llvm/projects/llvm-cbe/test/selectionsort
-$ ls
-main.c
-$ clang -S -emit-llvm -g main.c
-$ ls
-main.c main.ll
-$ $(HOME)/llvm/build/bin/llvm-cbe main.ll
+```sh
+    llvm-cbe$ cd test/selectionsort
+    selectionsort$ ls
+    main.c
+    selectionsort$ clang -S -emit-llvm -g main.c
+    selectionsort$ ls
+    main.c main.ll
+    selectionsort$ ../../build/tools/llvm-cbe/llvm-cbe main.ll
 ```
 
 You can find options to configure the C backend's output with `llvm-cbe --help`.
@@ -88,11 +88,11 @@ Look for options beginning with `--cbe-`.
 Compile Generated C Code and Run
 ================================
 
-```
-$ gcc -o main.cbe main.cbe.c
-$ ls
-main.c  main.cbe  main.cbe.c  main.ll
-$ ./main.cbe
+```sh
+    selectionsort$ gcc -o main.cbe main.cbe.c
+    selectionsort$ ls
+    main.c  main.cbe  main.cbe.c  main.ll
+    selectionsort$ ./main.cbe
 ```
 
 Running tests
@@ -101,8 +101,8 @@ Running tests
 Unit tests:
 
 ```sh
-    $ cd $HOME/llvm-project/llvm/build
-    $ make CBEUnitTests && projects/llvm-cbe/unittests/CWriterTest
+    llvm-project$ cd llvm/build
+    build$ make CBEUnitTests && projects/llvm-cbe/unittests/CWriterTest
 ```
 
 Note that you need to have passed `-DLLVM_INCLUDE_TESTS=1` to cmake if you used
@@ -114,8 +114,7 @@ Other tests:
 First, compile llvm-cbe, and install pytest (e.g. `pip install pytest`). Then:
 
 ```sh
-    $ cd $HOME/llvm-project/llvm/projects/llvm-cbe
-    $ pytest
+    llvm-cbe$ pytest
 ```
 
 You might have to adjust the llvm-cbe and lli paths in that configuration.