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package system
import (
"fmt"
"io"
"os"
"strconv"
"strings"
"github.com/opencontainers/runc/internal/pathrs"
)
// 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'
Parked State = 'P'
Idle State = 'I'
)
// 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"
case Parked:
return "parked"
case Idle:
return "idle" // kernel thread
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 {
// 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_t, error) {
var stat Stat_t
statFile, err := pathrs.ProcPidOpen(pid, "stat", os.O_RDONLY)
if err != nil {
return stat, err
}
defer statFile.Close()
bytes, err := io.ReadAll(statFile)
if err != nil {
return stat, err
}
return parseStat(string(bytes))
}
func parseStat(data string) (stat Stat_t, err error) {
// 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
// The fields are space-separated, see full description in proc(5).
//
// We are only interested in:
// * field 2: process name. It is the only field enclosed into
// parenthesis, as it can contain spaces (and parenthesis) inside.
// * field 3: process state, a single character (%c)
// * field 22: process start time, a long unsigned integer (%llu).
// 1. Look for the first '(' and the last ')' first, what's in between is Name.
// We expect at least 20 fields and a space after the last one.
const minAfterName = 20*2 + 1 // the min field is '0 '.
first := strings.IndexByte(data, '(')
if first < 0 || first+minAfterName >= len(data) {
return stat, fmt.Errorf("invalid stat data (no comm or too short): %q", data)
}
last := strings.LastIndexByte(data, ')')
if last <= first || last+minAfterName >= len(data) {
return stat, fmt.Errorf("invalid stat data (no comm or too short): %q", data)
}
stat.Name = data[first+1 : last]
// 2. Remove fields 1 and 2 and a space after. State is right after.
data = data[last+2:]
stat.State = State(data[0])
// 3. StartTime is field 22, data is at field 3 now, so we need to skip 19 spaces.
skipSpaces := 22 - 3
for first = 0; skipSpaces > 0 && first < len(data); first++ {
if data[first] == ' ' {
skipSpaces--
}
}
// Now first points to StartTime; look for space right after.
i := strings.IndexByte(data[first:], ' ')
if i < 0 {
return stat, fmt.Errorf("invalid stat data (too short): %q", data)
}
stat.StartTime, err = strconv.ParseUint(data[first:first+i], 10, 64)
if err != nil {
return stat, fmt.Errorf("invalid stat data (bad start time): %w", err)
}
return stat, nil
}
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