rancherOS/vendor/github.com/opencontainers/runc/libcontainer/utils/utils_unix.go

// +build !windows

package utils

import (
	"io/ioutil"
	"strconv"
	"syscall"
)

func CloseExecFrom(minFd int) error {
	fdList, err := ioutil.ReadDir("/proc/self/fd")
	if err != nil {
		return err
	}
	for _, fi := range fdList {
		fd, err := strconv.Atoi(fi.Name())
		if err != nil {
			// ignore non-numeric file names
			continue
		}

		if fd < minFd {
			// ignore descriptors lower than our specified minimum
			continue
		}

		// intentionally ignore errors from syscall.CloseOnExec
		syscall.CloseOnExec(fd)
		// the cases where this might fail are basically file descriptors that have already been closed (including and especially the one that was created when ioutil.ReadDir did the "opendir" syscall)
	}
	return nil
}