Merge pull request #130 from jonboulle/chrissnell-custom-journal-directory

*: add util.GetMachineID+journal.NewJournalFromDir

Author: jonboulle

sdjournal/journal.go

@@ -25,14 +25,15 @@
 package sdjournal
 
 /*
-#cgo pkg-config: libsystemd-journal
+#cgo pkg-config: libsystemd
 #include <systemd/sd-journal.h>
 #include <stdlib.h>
 #include <syslog.h>
 */
 import "C"
 import (
 	"fmt"
+	"path/filepath"
 	"sync"
 	"time"
 	"unsafe"
@@ -86,6 +87,27 @@ func NewJournal() (*Journal, error) {
 	return j, nil
 }
 
+// NewJournalFromDir returns a new Journal instance pointing to a journal residing
+// in a given directory. The supplied path may be relative or absolute; if
+// relative, it will be converted to an absolute path before being opened.
+func NewJournalFromDir(path string) (*Journal, error) {
+	path, err := filepath.Abs(path)
+	if err != nil {
+		return nil, err
+	}
+
+	p := C.CString(path)
+	defer C.free(unsafe.Pointer(p))
+
+	j := &Journal{}
+	err := C.sd_journal_open_directory(&j.cjournal, p, 0)
+	if err < 0 {
+		return nil, fmt.Errorf("failed to open journal in directory %v: %v", path, err)
+	}
+
+	return j, nil
+}
+
 // Close closes a journal opened with NewJournal.
 func (j *Journal) Close() error {
 	j.mu.Lock()

util/util.go

@@ -60,7 +60,9 @@ import "C"
 import (
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"os"
+	"strings"
 	"syscall"
 	"unsafe"
 )
@@ -244,7 +246,7 @@ func CurrentUnitName() (unit string, err error) {
 }
 
 // IsRunningSystemd checks whether the host was booted with systemd as its init
-// system. This functions similar to systemd's `sd_booted(3)`: internally, it
+// system. This functions similarly to systemd's `sd_booted(3)`: internally, it
 // checks whether /run/systemd/system/ exists and is a directory.
 // http://www.freedesktop.org/software/systemd/man/sd_booted.html
 func IsRunningSystemd() bool {
@@ -254,3 +256,15 @@ func IsRunningSystemd() bool {
 	}
 	return fi.IsDir()
 }
+
+// GetMachineID returns a host's 128-bit machine ID as a string. This functions
+// similarly to systemd's `sd_id128_get_machine`: internally, it simply reads
+// the contents of /etc/machine-id
+// http://www.freedesktop.org/software/systemd/man/sd_id128_get_machine.html
+func GetMachineID() (string, error) {
+	machineID, err := ioutil.ReadFile("/etc/machine-id")
+	if err != nil {
+		return "", fmt.Errorf("failed to read /etc/machine-id: %v", err)
+	}
+	return strings.TrimSpace(string(machineID)), nil
+}