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package system
import (
"fmt"
"io/ioutil"
"path/filepath"
"strconv"
"strings"
)
// State is the status of a process.
type State rune
const ( // Only values for Linux 3.14 and later are listed here
Dead State = 'X'
DiskSleep State = 'D'
Running State = 'R'
Sleeping State = 'S'
Stopped State = 'T'
TracingStop State = 't'
Zombie State = 'Z'
)
// String forms of the state from proc(5)'s documentation for
// /proc/[pid]/status' "State" field.
func (s State) String() string {
switch s {
case Dead:
return "dead"
case DiskSleep:
return "disk sleep"
case Running:
return "running"
case Sleeping:
return "sleeping"
case Stopped:
return "stopped"
case TracingStop:
return "tracing stop"
case Zombie:
return "zombie"
default:
return fmt.Sprintf("unknown (%c)", s)
}
}
// Stat_t represents the information from /proc/[pid]/stat, as
// described in proc(5) with names based on the /proc/[pid]/status
// fields.
type Stat_t struct {
// PID is the process ID.
PID uint
// Name is the command run by the process.
Name string
// State is the state of the process.
State State
// StartTime is the number of clock ticks after system boot (since
// Linux 2.6).
StartTime uint64
}
// Stat returns a Stat_t instance for the specified process.
func Stat(pid int) (stat Stat_t, err error) {
bytes, err := ioutil.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "stat"))
if err != nil {
return stat, err
}
return parseStat(string(bytes))
}
func parseStat(data string) (stat Stat_t, err error) {
// From proc(5), field 2 could contain space and is inside `(` and `)`.
// The following is an example:
// 89653 (gunicorn: maste) S 89630 89653 89653 0 -1 4194560 29689 28896 0 3 146 32 76 19 20 0 1 0 2971844 52965376 3920 18446744073709551615 1 1 0 0 0 0 0 16781312 137447943 0 0 0 17 1 0 0 0 0 0 0 0 0 0 0 0 0 0
i := strings.LastIndex(data, ")")
if i <= 2 || i >= len(data)-1 {
return stat, fmt.Errorf("invalid stat data: %q", data)
}
parts := strings.SplitN(data[:i], "(", 2)
if len(parts) != 2 {
return stat, fmt.Errorf("invalid stat data: %q", data)
}
stat.Name = parts[1]
_, err = fmt.Sscanf(parts[0], "%d", &stat.PID)
if err != nil {
return stat, err
}
// parts indexes should be offset by 3 from the field number given
// proc(5), because parts is zero-indexed and we've removed fields
// one (PID) and two (Name) in the paren-split.
parts = strings.Split(data[i+2:], " ")
var state int
fmt.Sscanf(parts[3-3], "%c", &state)
stat.State = State(state)
fmt.Sscanf(parts[22-3], "%d", &stat.StartTime)
return stat, nil
}
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