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48 lines
1.4 KiB
48 lines
1.4 KiB
// Copyright 2018 The Prometheus Authors |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// +build linux,!appengine |
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package util |
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import ( |
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"bytes" |
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"os" |
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"syscall" |
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) |
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// SysReadFile is a simplified ioutil.ReadFile that invokes syscall.Read directly. |
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// https://github.com/prometheus/node_exporter/pull/728/files |
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// |
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// Note that this function will not read files larger than 128 bytes. |
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func SysReadFile(file string) (string, error) { |
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f, err := os.Open(file) |
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if err != nil { |
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return "", err |
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} |
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defer f.Close() |
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// On some machines, hwmon drivers are broken and return EAGAIN. This causes |
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// Go's ioutil.ReadFile implementation to poll forever. |
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// |
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// Since we either want to read data or bail immediately, do the simplest |
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// possible read using syscall directly. |
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const sysFileBufferSize = 128 |
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b := make([]byte, sysFileBufferSize) |
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n, err := syscall.Read(int(f.Fd()), b) |
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if err != nil { |
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return "", err |
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} |
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return string(bytes.TrimSpace(b[:n])), nil |
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}
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