Add os-release parser

cmd/os_release.go

@@ -0,0 +1,55 @@
+package cmd
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	vfs "github.com/twpayne/go-vfs"
+)
+
+// getOSRelease returns the operating system identification data as defined by
+// https://www.freedesktop.org/software/systemd/man/os-release.html.
+func getOSRelease(fs vfs.FS) (map[string]string, error) {
+	for _, filename := range []string{"/usr/lib/os-release", "/etc/os-release"} {
+		f, err := fs.Open(filename)
+		if os.IsNotExist(err) {
+			continue
+		} else if err != nil {
+			return nil, err
+		}
+		defer f.Close()
+		return parseOSRelease(f)
+	}
+	return nil, os.ErrNotExist
+}
+
+// maybeUnquote removes quotation marks around s.
+func maybeUnquote(s string) string {
+	// Try to unquote.
+	if s, err := strconv.Unquote(s); err == nil {
+		return s
+	}
+	// Otherwise return s, unchanged.
+	return s
+}
+
+// parseOSRelease parses operating system identification data from r as defined
+// by https://www.freedesktop.org/software/systemd/man/os-release.html.
+func parseOSRelease(r io.Reader) (map[string]string, error) {
+	result := make(map[string]string)
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		fields := strings.SplitN(s.Text(), "=", 2)
+		if len(fields) != 2 {
+			return nil, fmt.Errorf("cannot parse %q", s.Text())
+		}
+		key := fields[0]
+		value := maybeUnquote(fields[1])
+		result[key] = value
+	}
+	return result, s.Err()
+}

cmd/os_release_test.go

@@ -0,0 +1,72 @@
+package cmd
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/d4l3k/messagediff"
+)
+
+func TestParseOSRelease(t *testing.T) {
+	for _, tc := range []struct {
+		s    string
+		want map[string]string
+	}{
+		{
+			s: `NAME=Fedora
+VERSION="17 (Beefy Miracle)"
+ID=fedora
+VERSION_ID=17
+PRETTY_NAME="Fedora 17 (Beefy Miracle)"
+ANSI_COLOR="0;34"
+CPE_NAME="cpe:/o:fedoraproject:fedora:17"
+HOME_URL="https://fedoraproject.org/"
+BUG_REPORT_URL="https://bugzilla.redhat.com/"`,
+			want: map[string]string{
+				"NAME":           "Fedora",
+				"VERSION":        "17 (Beefy Miracle)",
+				"ID":             "fedora",
+				"VERSION_ID":     "17",
+				"PRETTY_NAME":    "Fedora 17 (Beefy Miracle)",
+				"ANSI_COLOR":     "0;34",
+				"CPE_NAME":       "cpe:/o:fedoraproject:fedora:17",
+				"HOME_URL":       "https://fedoraproject.org/",
+				"BUG_REPORT_URL": "https://bugzilla.redhat.com/",
+			},
+		},
+		{
+			s: `NAME="Ubuntu"
+VERSION="18.04.1 LTS (Bionic Beaver)"
+ID=ubuntu
+ID_LIKE=debian
+PRETTY_NAME="Ubuntu 18.04.1 LTS"
+VERSION_ID="18.04"
+HOME_URL="https://www.ubuntu.com/"
+SUPPORT_URL="https://help.ubuntu.com/"
+BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
+PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
+VERSION_CODENAME=bionic
+UBUNTU_CODENAME=bionic`,
+			want: map[string]string{
+				"NAME":               "Ubuntu",
+				"VERSION":            "18.04.1 LTS (Bionic Beaver)",
+				"ID":                 "ubuntu",
+				"ID_LIKE":            "debian",
+				"PRETTY_NAME":        "Ubuntu 18.04.1 LTS",
+				"VERSION_ID":         "18.04",
+				"HOME_URL":           "https://www.ubuntu.com/",
+				"SUPPORT_URL":        "https://help.ubuntu.com/",
+				"BUG_REPORT_URL":     "https://bugs.launchpad.net/ubuntu/",
+				"PRIVACY_POLICY_URL": "https://www.ubuntu.com/legal/terms-and-policies/privacy-policy",
+				"VERSION_CODENAME":   "bionic",
+				"UBUNTU_CODENAME":    "bionic",
+			},
+		},
+	} {
+		got, gotErr := parseOSRelease(bytes.NewBufferString(tc.s))
+		diff, equal := messagediff.PrettyDiff(tc.want, got)
+		if gotErr != nil || !equal {
+			t.Errorf("parseOSRelease(bytes.NewBufferString(%q)) == %+v, %v, want %+v, <nil>\n%s", tc.s, got, gotErr, tc.want, diff)
+		}
+	}
+}