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