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pids.go
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pids.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2019-2020 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package cgroup
import (
"bufio"
"fmt"
"io"
"os"
"strconv"
)
// pidsInFile returns the list of process IDs in a given file.
func pidsInFile(fname string) ([]int, error) {
file, err := os.Open(fname)
if os.IsNotExist(err) {
return nil, nil
}
if err != nil {
return nil, err
}
defer file.Close()
return parsePids(bufio.NewReader(file))
}
// parsePids parses a list of pids, one per line, from a reader.
func parsePids(reader io.Reader) ([]int, error) {
scanner := bufio.NewScanner(reader)
var pids []int
for scanner.Scan() {
s := scanner.Text()
pid, err := parsePid(s)
if err != nil {
return nil, err
}
pids = append(pids, pid)
}
if err := scanner.Err(); err != nil {
return nil, err
}
return pids, nil
}
// parsePid parses a string as a process identifier.
func parsePid(text string) (int, error) {
pid, err := strconv.Atoi(text)
if err != nil || (err == nil && pid <= 0) {
return 0, fmt.Errorf("cannot parse pid %q", text)
}
return pid, err
}