added docu

README.md

@@ -1,2 +1,133 @@
 # nbtreader
- Parse and show Minecrafts NBT files in the command-line.
+
+Parse and show Minecrafts NBT files in the command-line.
+
+## Installing
+
+Clone repo and build `cli` with Go
+
+```sh
+go build -o nbtreader ./cli
+```
+
+PS: For Windows its recommended to add a `.exe` to the filename:
+
+```bash
+go build -o nbtreader ./cli
+```
+
+This produces an ready-to-use executable file named `nbtreader` (or `nbtreader.exe`). See [next Section](#usage) for using the command and its syntax.
+
+You may want to add a symlink in your PATH to this file, so you can use this executable systemwide. In the following examples I call the command `nbtreader` to call the file.
+
+## Usage
+
+After installation the binary can be used simply by passing a filename as argument:
+
+```sh
+nbtreader files/test.dat
+```
+
+produces
+
+```
+{
+  name: "Bananrama"
+}
+```
+
+and
+
+```sh
+nbtreader files/bigtest.nbt
+```
+
+produces
+
+```
+{
+  longTest: 9223372036854775807l,
+  shortTest: 32767s,
+  stringTest: "HELLO WORLD THIS IS A TEST STRING ÅÄÖ!",
+  floatTest: 0.49823147f,
+  intTest: 2147483647,
+  nested compound test: {
+    ham: {
+      name: "Hampus",
+      value: 0.75f
+    },
+    egg: {
+      name: "Eggbert",
+      value: 0.5f
+    }
+  },
+  listTest (long): [11l, 12l, 13l, 14l, 15l],
+  listTest (compound): [{
+    name: "Compound tag #0",
+    created-on: 1264099775885l
+  }, {
+    name: "Compound tag #1",
+    created-on: 1264099775885l
+  }],
+  byteTest: 127b,
+  byteArrayTest (the first 1000 values of (n*n*255+n*7)%100, starting with n=0 (0, 62, 34, 16, 8, ...)): [B; 0b, 62b, <trimmed 996 values>, 6b, 48b],
+  doubleTest: 0.4931287132182315d
+}
+```
+
+If no file is given, nbtreader reads from stdin:
+
+```sh
+# e.g. with pipe
+cat files/test.nbt | nbtreader
+# or redirect
+nbreader < files/test.nbt
+```
+
+### Flags
+
+Available flags are
+
+- `-inType <string>`
+- `-outType <string>`
+- `-out <string>`
+
+#### Flag `inType` and `outType`
+
+With theese flags you can specify the in- and output type.
+
+Current valid values for `inType`:
+- `NBT` *(default if ommited)*
+
+Current valid values for `outType`:
+- `JSON`
+- `NJSON` *([see spec](https://docs.google.com/spreadsheets/u/0/d/1Z0XVvyfzVSGstmpLSMKnwlxwYg8N2ZFl3Xmh0ZV0yZU/htmlview#gid=0))*
+- `SNBT` *(default if ommited)*
+
+Example:
+
+```sh
+nbtreader -outType JSON files/test.nbt
+```
+
+produces
+
+```json
+{
+	"name": "Bananrama"
+}
+```
+
+#### Flag `out`
+
+To easily save the result in a file you could once again use redirecting:
+
+```sh
+nbtreader files/test.nbt > files output.txt
+```
+
+However, if you pass in the optional flag `-out <filename>` the output is instead written to the given filename:
+
+```sh
+nbtreader -out files/output.txt files/test.nbt
+```