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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
//go:build aix || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos
// +build aix dragonfly freebsd linux netbsd openbsd solaris zos
package resource // import "go.opentelemetry.io/otel/sdk/resource"
import (
"bufio"
"fmt"
"io"
"os"
"strings"
)
// osRelease builds a string describing the operating system release based on the
// properties of the os-release file. If no os-release file is found, or if the
// required properties to build the release description string are missing, an empty
// string is returned instead. For more information about os-release files, see:
// https://www.freedesktop.org/software/systemd/man/os-release.html
func osRelease() string {
file, err := getOSReleaseFile()
if err != nil {
return ""
}
defer file.Close()
values := parseOSReleaseFile(file)
return buildOSRelease(values)
}
// getOSReleaseFile returns a *os.File pointing to one of the well-known os-release
// files, according to their order of preference. If no file can be opened, it
// returns an error.
func getOSReleaseFile() (*os.File, error) {
return getFirstAvailableFile([]string{"/etc/os-release", "/usr/lib/os-release"})
}
// parseOSReleaseFile process the file pointed by `file` as an os-release file and
// returns a map with the key-values contained in it. Empty lines or lines starting
// with a '#' character are ignored, as well as lines with the missing key=value
// separator. Values are unquoted and unescaped.
func parseOSReleaseFile(file io.Reader) map[string]string {
values := make(map[string]string)
scanner := bufio.NewScanner(file)
for scanner.Scan() {
line := scanner.Text()
if skip(line) {
continue
}
key, value, ok := parse(line)
if ok {
values[key] = value
}
}
return values
}
// skip returns true if the line is blank or starts with a '#' character, and
// therefore should be skipped from processing.
func skip(line string) bool {
line = strings.TrimSpace(line)
return len(line) == 0 || strings.HasPrefix(line, "#")
}
// parse attempts to split the provided line on the first '=' character, and then
// sanitize each side of the split before returning them as a key-value pair.
func parse(line string) (string, string, bool) {
k, v, found := strings.Cut(line, "=")
if !found || len(k) == 0 {
return "", "", false
}
key := strings.TrimSpace(k)
value := unescape(unquote(strings.TrimSpace(v)))
return key, value, true
}
// unquote checks whether the string `s` is quoted with double or single quotes
// and, if so, returns a version of the string without them. Otherwise it returns
// the provided string unchanged.
func unquote(s string) string {
if len(s) < 2 {
return s
}
if (s[0] == '"' || s[0] == '\'') && s[0] == s[len(s)-1] {
return s[1 : len(s)-1]
}
return s
}
// unescape removes the `\` prefix from some characters that are expected
// to have it added in front of them for escaping purposes.
func unescape(s string) string {
return strings.NewReplacer(
`\$`, `$`,
`\"`, `"`,
`\'`, `'`,
`\\`, `\`,
"\\`", "`",
).Replace(s)
}
// buildOSRelease builds a string describing the OS release based on the properties
// available on the provided map. It favors a combination of the `NAME` and `VERSION`
// properties as first option (falling back to `VERSION_ID` if `VERSION` isn't
// found), and using `PRETTY_NAME` alone if some of the previous are not present. If
// none of these properties are found, it returns an empty string.
//
// The rationale behind not using `PRETTY_NAME` as first choice was that, for some
// Linux distributions, it doesn't include the same detail that can be found on the
// individual `NAME` and `VERSION` properties, and combining `PRETTY_NAME` with
// other properties can produce "pretty" redundant strings in some cases.
func buildOSRelease(values map[string]string) string {
var osRelease string
name := values["NAME"]
version := values["VERSION"]
if version == "" {
version = values["VERSION_ID"]
}
if name != "" && version != "" {
osRelease = fmt.Sprintf("%s %s", name, version)
} else {
osRelease = values["PRETTY_NAME"]
}
return osRelease
}
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