blob: c07de0b6c9c6aba295a2c70e48b6f605430cc921 [file] [log] [blame]
khenaidoo26721882021-08-11 17:42:52 -04001// Copyright 2018 The Prometheus Authors
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6// http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13
14// +build linux,!appengine
15
16package util
17
18import (
19 "bytes"
20 "os"
21 "syscall"
22)
23
24// SysReadFile is a simplified ioutil.ReadFile that invokes syscall.Read directly.
25// https://github.com/prometheus/node_exporter/pull/728/files
26//
27// Note that this function will not read files larger than 128 bytes.
28func SysReadFile(file string) (string, error) {
29 f, err := os.Open(file)
30 if err != nil {
31 return "", err
32 }
33 defer f.Close()
34
35 // On some machines, hwmon drivers are broken and return EAGAIN. This causes
36 // Go's ioutil.ReadFile implementation to poll forever.
37 //
38 // Since we either want to read data or bail immediately, do the simplest
39 // possible read using syscall directly.
40 const sysFileBufferSize = 128
41 b := make([]byte, sysFileBufferSize)
42 n, err := syscall.Read(int(f.Fd()), b)
43 if err != nil {
44 return "", err
45 }
46
47 return string(bytes.TrimSpace(b[:n])), nil
48}