diff --git a/README.md b/README.md
index a7925c4..a80dd9e 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,40 @@
 # pidusage
 Cross-platform process cpu % and memory usage of a PID for golang
+
+Ideas from https://github.com/soyuka/pidusage but just use Golang
+
+## API
+
+```golang
+import (
+  "os"
+	"github.com/struCoder/pmgo/lib/utils"
+)
+
+func printStat() {
+	sysInfo := pidusage.GetStat(os.Process.Pid)
+}
+```
+
+## How it works
+
+A check on the `runtime.GOOS` is done to determine the method to use.
+
+### Linux
+We use `/proc/{pid}/stat` in addition to the the `PAGE_SIZE` and the `CLK_TCK` direclty from `getconf()` command. Uptime comes from `proc/uptime` file because it's more accurate than the nodejs `os.uptime()`.
+
+Cpu usage is computed by following [those instructions](http://stackoverflow.com/questions/16726779/how-do-i-get-the-total-cpu-usage-of-an-application-from-proc-pid-stat/16736599#16736599). It keeps an history of the current processor time for the given pid so that the computed value gets more and more accurate. Don't forget to do `unmonitor(pid)` so that history gets cleared.
+Cpu usage does not check the child process tree!
+
+Memory result is representing the RSS (resident set size) only by doing `rss*pagesize`, where `pagesize` is the result of `getconf PAGE_SIZE`.
+
+### On darwin, freebsd, solaris (tested on 10/11)
+We use a fallback with the `ps -o pcpu,rss -p PID` command to get the same informations.
+
+Memory usage will also display the RSS only, process cpu usage might differ from a distribution to another. Please check the correspoding `man ps` for more insights on the subject.
+
+### On AIX
+AIX is tricky because I have no AIX test environement, at the moment we use: `ps -o pcpu,rssize -p PID` but `/proc` results should be more accurate! If you're familiar with the AIX environment and know how to get the same results as we've got with Linux systems.
+
+### Windows
+Next version will support
diff --git a/pidusage.go b/pidusage.go
new file mode 100644
index 0000000..717b5b2
--- /dev/null
+++ b/pidusage.go
@@ -0,0 +1,146 @@
+package pidusage
+
+import (
+	"io/ioutil"
+	"math"
+	"os/exec"
+	"path"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+// SysInfo will record cpu and memory data
+type SysInfo struct {
+	CPU    float64
+	Memory float64
+}
+
+// Stat will store CUP time struct
+type Stat struct {
+	utime  float64
+	stime  float64
+	cutime float64
+	cstime float64
+	start  float64
+	rss    float64
+	uptime float64
+}
+
+type fn func(int) *SysInfo
+
+var fnMap map[string]fn
+var platform string
+var history map[int]Stat
+var eol string
+
+func wrapper(statType string) func(pid int) *SysInfo {
+	return func(pid int) *SysInfo {
+		return stat(pid, statType)
+	}
+}
+func init() {
+	platform = runtime.GOOS
+	eol = "\n"
+	if strings.Index(platform, "win") == 0 {
+		platform = "win"
+		eol = "\r\n"
+	}
+	history = make(map[int]Stat)
+	fnMap = make(map[string]fn)
+	fnMap["darwin"] = wrapper("ps")
+	fnMap["sunos"] = wrapper("ps")
+	fnMap["freebsd"] = wrapper("ps")
+	fnMap["aix"] = wrapper("ps")
+	fnMap["linux"] = wrapper("proc")
+	fnMap["netbsd"] = wrapper("proc")
+	fnMap["win"] = wrapper("win")
+}
+func formatStdOut(stdout []byte, userfulIndex int) []string {
+	infoArr := strings.Split(string(stdout), eol)[userfulIndex]
+	ret := strings.Fields(infoArr)
+	return ret
+}
+
+func parseFloat(val string) float64 {
+	floatVal, _ := strconv.ParseFloat(val, 64)
+	return floatVal
+}
+
+func stat(pid int, statType string) *SysInfo {
+	sysInfo := &SysInfo{}
+	_history := history[pid]
+	if statType == "ps" {
+		args := "-o pcpu,rss -p"
+		if platform == "aix" {
+			args = "-o pcpu,rssize -p"
+		}
+		stdout, _ := exec.Command("ps", args, strconv.Itoa(pid)).Output()
+		ret := formatStdOut(stdout, 1)
+		sysInfo.CPU = parseFloat(ret[0])
+		sysInfo.Memory = parseFloat(ret[1]) * 1024
+	} else if statType == "proc" {
+		// default clkTck and pageSize
+		var clkTck float64 = 100
+		var pageSize float64 = 4096
+
+		uptimeFileBytes, err := ioutil.ReadFile(path.Join("/proc", "uptime"))
+		uptime := parseFloat(strings.Split(string(uptimeFileBytes), " ")[0])
+
+		clkTckStdout, err := exec.Command("getconf", "CLK_TCK").Output()
+		if err == nil {
+			clkTck = parseFloat(formatStdOut(clkTckStdout, 0)[0])
+		}
+
+		pageSizeStdout, err := exec.Command("getconf", "PAGESIZE").Output()
+		if err == nil {
+			pageSize = parseFloat(formatStdOut(pageSizeStdout, 0)[0])
+		}
+
+		procStatFileBytes, err := ioutil.ReadFile(path.Join("/proc", strconv.Itoa(pid), "stat"))
+		infos := strings.Split(strings.SplitAfter(string(procStatFileBytes), ")")[1], " ")
+		stat := &Stat{
+			utime:  parseFloat(infos[12]),
+			stime:  parseFloat(infos[13]),
+			cutime: parseFloat(infos[14]),
+			cstime: parseFloat(infos[15]),
+			start:  parseFloat(infos[20]) / clkTck,
+			rss:    parseFloat(infos[22]),
+			uptime: uptime,
+		}
+
+		_stime := 0.0
+		_utime := 0.0
+		if _history.stime != 0 {
+			_stime = _history.stime
+		}
+
+		if _history.utime != 0 {
+			_utime = _history.utime
+		}
+		total := stat.stime - _stime + stat.utime - _utime
+		total = total / clkTck
+
+		seconds := stat.start - uptime
+		if _history.uptime != 0 {
+			seconds = uptime - _history.uptime
+		}
+
+		seconds = math.Abs(seconds)
+		if seconds == 0 {
+			seconds = 1
+		}
+
+		history[pid] = *stat
+		sysInfo.CPU = (total / seconds) * 100
+		sysInfo.Memory = stat.rss * pageSize
+	}
+	return sysInfo
+
+}
+
+// GetStat will return current system CPU and memory data
+func GetStat(pid int) *SysInfo {
+	sysInfo := fnMap[platform](pid)
+	return sysInfo
+}
diff --git a/pidusage_test.go b/pidusage_test.go
new file mode 100644
index 0000000..e69de29