Function SysReadFile

internal/util/sysreadfile.go:30–50

SysReadFile is a simplified os.ReadFile that invokes syscall.Read directly. https://github.com/prometheus/node_exporter/pull/728/files Note that this function will not read files larger than 128 bytes.

(file string)

//
// Note that this function will not read files larger than 128 bytes.
func SysReadFile(file string) (string, error) {
	f, err := os.Open(file)
	if err != nil {
		return "", err
	}
	defer f.Close()

	// On some machines, hwmon drivers are broken and return EAGAIN.  This causes
	// Go's os.ReadFile implementation to poll forever.
	//
	// Since we either want to read data or bail immediately, do the simplest
	// possible read using syscall directly.
	const sysFileBufferSize = 128
	b := make([]byte, sysFileBufferSize)
	n, err := syscall.Read(int(f.Fd()), b)
	if err != nil {
		return "", err
	}

	return string(bytes.TrimSpace(b[:n])), nil
}

// SysReadUintFromFile reads a file using SysReadFile and attempts to parse a uint64 from it.
func SysReadUintFromFile(path string) (uint64, error) {