DockerCLI/vendor/github.com/opencontainers/runc/libcontainer/system/proc.go

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package system
import (
"io/ioutil"
"path/filepath"
"strconv"
"strings"
)
// look in /proc to find the process start time so that we can verify
// that this pid has started after ourself
func GetProcessStartTime(pid int) (string, error) {
data, err := ioutil.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "stat"))
if err != nil {
return "", err
}
return parseStartTime(string(data))
}
func parseStartTime(stat string) (string, error) {
// the starttime is located at pos 22
// from the man page
//
// starttime %llu (was %lu before Linux 2.6)
// (22) The time the process started after system boot. In kernels before Linux 2.6, this
// value was expressed in jiffies. Since Linux 2.6, the value is expressed in clock ticks
// (divide by sysconf(_SC_CLK_TCK)).
//
// NOTE:
// pos 2 could contain space and is inside `(` and `)`:
// (2) comm %s
// The filename of the executable, in parentheses.
// This is visible whether or not the executable is
// swapped out.
//
// 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
// get parts after last `)`:
s := strings.Split(stat, ")")
parts := strings.Split(strings.TrimSpace(s[len(s)-1]), " ")
return parts[22-3], nil // starts at 3 (after the filename pos `2`)
}