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// Copyright 2018 psgo authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package host extracts data from the host, such as the system's boot time or
// the tick rate of the system clock.
package host
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
// BootTime parses /proc/uptime returns the boot time in seconds since the
// Epoch, 1970-01-01 00:00:00 +0000 (UTC).
func BootTime() (int64, error) {
if bootTime != nil {
return *bootTime, nil
}
f, err := os.Open("/proc/stat")
if err != nil {
return 0, err
}
btimeStr := ""
scanner := bufio.NewScanner(f)
for scanner.Scan() {
fields := strings.Fields(scanner.Text())
if len(fields) < 2 {
continue
}
if fields[0] == "btime" {
btimeStr = fields[1]
}
}
if len(btimeStr) == 0 {
return 0, fmt.Errorf("couldn't extract boot time from /proc/stat")
}
btimeSec, err := strconv.ParseInt(btimeStr, 10, 64)
if err != nil {
return 0, fmt.Errorf("error parsing boot time from /proc/stat: %w", err)
}
bootTime = &btimeSec
return btimeSec, nil
}
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