check stderr before reporting back error 1

README.md

@@ -40,17 +40,17 @@ import (
     "log"
     "time"
 
-    "github.com/taigrr/systemctl/v1"
+    "github.com/taigrr/systemctl"
 )
 
 func main() {
     ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
     defer cancel()
-
-    // Equivalent to `systemctl enable dhcpd` with a 10 second timeout
-    err := systemctl.Enable(ctx, "dhcpd")
+    userMode := false
+    // Equivalent to `systemctl enable nginx` with a 10 second timeout
+    err := systemctl.Enable(ctx, "nginx", userMode)
     if err != nil {
-        log.Fatalf("unable to enable unit %s: %v", "dhcpd", err)
+        log.Fatalf("unable to enable unit %s: %v", "nginx", err)
     }
 }
 ```

errors.go

@@ -17,4 +17,6 @@ var (
 
 	// ErrDoesNotExist means the unit specified doesn't exist or can't be found
 	ErrDoesNotExist = errors.New("Unit does not exist")
+	// ErrUnspecified means something in the stderr output contains the word `Failed`, but not a known case
+	ErrUnspecified = errors.New("Unknown error")
 )

systemctl.go

@@ -2,8 +2,7 @@ package systemctl
 
 import (
 	"context"
-	"errors"
-	"strconv"
+	"fmt"
 )
 
 // TODO
@@ -44,22 +43,36 @@ func Enable(ctx context.Context, unit string, usermode bool) error {
 		args[1] = "--user"
 	}
 	_, stderr, code, err := execute(ctx, args)
-
-	if err != nil {
-		return err
+	customErr := filterErr(stderr)
+	if customErr != nil {
+		return customErr
 	}
-	err = filterErr(stderr)
 	if err != nil {
 		return err
 	}
 	if code != 0 {
-		return errors.New("received error code " + strconv.Itoa(code))
+		return fmt.Errorf("received error code %d for stderr `%s`: %w", code, stderr, ErrUnspecified)
 	}
 	return nil
 }
 
 // TODO
 func Disable(ctx context.Context, unit string, usermode bool) error {
+	var args = []string{"disable", "--system", unit}
+	if usermode {
+		args[1] = "--user"
+	}
+	_, stderr, code, err := execute(ctx, args)
+	customErr := filterErr(stderr)
+	if customErr != nil {
+		return customErr
+	}
+	if err != nil {
+		return err
+	}
+	if code != 0 {
+		return fmt.Errorf("received error code %d for stderr `%s`: %w", code, stderr, ErrUnspecified)
+	}
 	return nil
 }
 

systemctl_test.go

@@ -0,0 +1,28 @@
+package systemctl
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestEnableNonexistant(t *testing.T) {
+	unit := "nonexistant"
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	defer cancel()
+	err := Enable(ctx, unit, true)
+	if err != ErrDoesNotExist {
+		t.Errorf("error is %v, but should have been %v", err, ErrDoesNotExist)
+	}
+
+}
+func TestEnableNoPermissions(t *testing.T) {
+	unit := "nginx"
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	defer cancel()
+	err := Enable(ctx, unit, false)
+	if err != ErrInsufficientPermissions {
+		t.Errorf("error is %v, but should have been %v", err, ErrInsufficientPermissions)
+	}
+
+}

util.go

@@ -45,6 +45,19 @@ func filterErr(stderr string) error {
 	if matched {
 		return ErrDoesNotExist
 	}
+	matched, _ = regexp.MatchString(`Interactive authentication required`, stderr)
+	if matched {
+		return ErrInsufficientPermissions
+	}
+	matched, _ = regexp.MatchString(`Access denied`, stderr)
+	if matched {
+		return ErrInsufficientPermissions
+	}
+
+	matched, _ = regexp.MatchString(`Failed`, stderr)
+	if matched {
+		return ErrUnspecified
+	}
 
 	return nil
 }