Add unit reload support

filterErr checked 'does not exist' before 'Interactive authentication
required', so when systemd printed both (common for mask/unmask on
non-installed units as a non-root user), the wrong error was returned.

Reorder checks so permission, bus, and masked errors take priority over
existence warnings. Add tests covering mixed-stderr scenarios.

Also:
- CI: install and start nginx so user + root tests pass
- CI: run tests as both user and root for full coverage
- Bump Go 1.26 → 1.26.1

.github/workflows/ci.yml

@@ -0,0 +1,65 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Test (Go ${{ matrix.go-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: ["1.26"]
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+          cache: true
+
+      - name: Install and start nginx
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y -qq nginx
+          sudo systemctl start nginx
+          sudo systemctl enable nginx
+
+      - name: Run tests (user)
+        run: go test -race -coverprofile=coverage-user.out -covermode=atomic ./...
+
+      - name: Run tests (root)
+        run: sudo go test -race -coverprofile=coverage-root.out -covermode=atomic ./...
+
+      - name: Upload coverage to Codecov
+        if: matrix.go-version == '1.26'
+        uses: codecov/codecov-action@v5
+        with:
+          files: coverage-user.out,coverage-root.out
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: false
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.26"
+          cache: true
+
+      - name: Run staticcheck
+        uses: dominikh/staticcheck-action@v1
+        with:
+          version: latest
+          install-go: false

README.md

@@ -22,6 +22,7 @@ If your system isn't running (or targeting another system running) `systemctl`,
 - [x] `systemctl is-enabled`
 - [x] `systemctl is-failed`
 - [x] `systemctl mask`
+- [x] `systemctl reload`
 - [x] `systemctl restart`
 - [x] `systemctl show`
 - [x] `systemctl start`

errors_test.go

@@ -13,10 +13,10 @@ import (
 
 func TestErrorFuncs(t *testing.T) {
 	errFuncs := []func(ctx context.Context, unit string, opts Options) error{
-		Enable,
+		func(ctx context.Context, unit string, opts Options) error { return Enable(ctx, unit, opts) },
-		Disable,
+		func(ctx context.Context, unit string, opts Options) error { return Disable(ctx, unit, opts) },
-		Restart,
+		func(ctx context.Context, unit string, opts Options) error { return Restart(ctx, unit, opts) },
-		Start,
+		func(ctx context.Context, unit string, opts Options) error { return Start(ctx, unit, opts) },
 	}
 	errCases := []struct {
 		unit      string

filtererr_test.go

@@ -0,0 +1,134 @@
+package systemctl
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestFilterErr(t *testing.T) {
+	tests := []struct {
+		name   string
+		stderr string
+		want   error
+	}{
+		{
+			name:   "empty stderr",
+			stderr: "",
+			want:   nil,
+		},
+		{
+			name:   "unit does not exist",
+			stderr: "Unit foo.service does not exist, proceeding anyway.",
+			want:   ErrDoesNotExist,
+		},
+		{
+			name:   "unit not found",
+			stderr: "Unit foo.service not found.",
+			want:   ErrDoesNotExist,
+		},
+		{
+			name:   "unit not loaded",
+			stderr: "Unit foo.service not loaded.",
+			want:   ErrUnitNotLoaded,
+		},
+		{
+			name:   "no such file or directory",
+			stderr: "No such file or directory",
+			want:   ErrDoesNotExist,
+		},
+		{
+			name:   "interactive authentication required",
+			stderr: "Interactive authentication required.",
+			want:   ErrInsufficientPermissions,
+		},
+		{
+			name:   "access denied",
+			stderr: "Access denied",
+			want:   ErrInsufficientPermissions,
+		},
+		{
+			name:   "dbus session bus address",
+			stderr: "Failed to connect to bus: $DBUS_SESSION_BUS_ADDRESS not set",
+			want:   ErrBusFailure,
+		},
+		{
+			name:   "unit is masked",
+			stderr: "Unit foo.service is masked.",
+			want:   ErrMasked,
+		},
+		{
+			name:   "generic failed",
+			stderr: "Failed to do something unknown",
+			want:   ErrUnspecified,
+		},
+		{
+			name:   "does not exist with auth required prioritizes permission error",
+			stderr: "Unit nginx.service does not exist, proceeding anyway.\nFailed to mask unit: Interactive authentication required.",
+			want:   ErrInsufficientPermissions,
+		},
+		{
+			name:   "does not exist with access denied prioritizes permission error",
+			stderr: "Unit foo.service does not exist, proceeding anyway.\nAccess denied",
+			want:   ErrInsufficientPermissions,
+		},
+		{
+			name:   "does not exist with bus failure prioritizes bus error",
+			stderr: "Unit foo.service does not exist, proceeding anyway.\n$DBUS_SESSION_BUS_ADDRESS not set",
+			want:   ErrBusFailure,
+		},
+		{
+			name:   "unrecognized warning",
+			stderr: "Warning: something benign happened",
+			want:   nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := filterErr(tt.stderr)
+			if tt.want == nil {
+				if got != nil {
+					t.Errorf("filterErr(%q) = %v, want nil", tt.stderr, got)
+				}
+				return
+			}
+			if !errors.Is(got, tt.want) {
+				t.Errorf("filterErr(%q) = %v, want error wrapping %v", tt.stderr, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestHasValidUnitSuffix(t *testing.T) {
+	tests := []struct {
+		unit string
+		want bool
+	}{
+		{"nginx.service", true},
+		{"sshd.socket", true},
+		{"backup.timer", true},
+		{"dev-sda1.device", true},
+		{"home.mount", true},
+		{"dev-sda1.swap", true},
+		{"user.slice", true},
+		{"multi-user.target", true},
+		{"session-1.scope", true},
+		{"foo.automount", true},
+		{"backup.path", true},
+		{"foo.snapshot", true},
+		{"nginx", false},
+		{"", false},
+		{"foo.bar", false},
+		{"foo.services", false},
+		{".service", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.unit, func(t *testing.T) {
+			got := HasValidUnitSuffix(tt.unit)
+			if got != tt.want {
+				t.Errorf("HasValidUnitSuffix(%q) = %v, want %v", tt.unit, got, tt.want)
+			}
+		})
+	}
+}

go.mod

@@ -1,3 +1,3 @@
 module github.com/taigrr/systemctl
 
-go 1.26
+go 1.26.1

helpers.go

@@ -32,7 +32,23 @@ func GetNumRestarts(ctx context.Context, unit string, opts Options) (int, error)
 	if err != nil {
 		return -1, err
 	}
-	return strconv.Atoi(value)
+	if value == "[not set]" {
+		return -1, ErrValueNotSet
+	}
+	restarts, err := strconv.Atoi(value)
+	if err != nil {
+		return -1, err
+	}
+	// systemd returns NRestarts=0 for both genuinely zero-restart units and
+	// nonexistent/unloaded units. Disambiguate by checking LoadState: if the
+	// unit isn't loaded, the value is meaningless.
+	if restarts == 0 {
+		loadState, loadErr := Show(ctx, unit, properties.LoadState, opts)
+		if loadErr == nil && loadState == "not-found" {
+			return -1, ErrValueNotSet
+		}
+	}
+	return restarts, nil
 }
 
 // Get current memory in bytes (`systemctl show [unit] --property MemoryCurrent`) as an int

helpers_test.go

@@ -105,8 +105,8 @@ func TestGetNumRestarts(t *testing.T) {
 
 		// try nonexistant unit in user mode as user
 		{"nonexistant", ErrValueNotSet, Options{UserMode: false}, true},
-		// try existing unit in user mode as user
+		// try existing unit in user mode as user (loaded, so NRestarts=0 is valid)
-		{"syncthing", ErrValueNotSet, Options{UserMode: true}, true},
+		{"syncthing", nil, Options{UserMode: true}, true},
 		// try existing unit in system mode as user
 		{"nginx", nil, Options{UserMode: false}, true},
 

reload_linux_test.go

@@ -0,0 +1,67 @@
+//go:build linux
+
+package systemctl
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestReloadBuildsExpectedCommand(t *testing.T) {
+	tests := []struct {
+		name string
+		opts Options
+		want []string
+	}{
+		{
+			name: "system mode",
+			opts: Options{},
+			want: []string{"reload", "--system", "nginx.service"},
+		},
+		{
+			name: "user mode",
+			opts: Options{UserMode: true},
+			want: []string{"reload", "--user", "nginx.service"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tempDir := t.TempDir()
+			logFile := filepath.Join(tempDir, "args.log")
+			fakeSystemctl := filepath.Join(tempDir, "systemctl")
+			script := "#!/bin/sh\nprintf '%s\\n' \"$@\" > '" + logFile + "'\n"
+
+			if err := os.WriteFile(fakeSystemctl, []byte(script), 0o755); err != nil {
+				t.Fatalf("write fake systemctl: %v", err)
+			}
+
+			original := systemctl
+			systemctl = fakeSystemctl
+			t.Cleanup(func() {
+				systemctl = original
+			})
+
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			defer cancel()
+
+			if err := Reload(ctx, "nginx.service", tt.opts); err != nil {
+				t.Fatalf("Reload returned error: %v", err)
+			}
+
+			gotBytes, err := os.ReadFile(logFile)
+			if err != nil {
+				t.Fatalf("read captured args: %v", err)
+			}
+			got := strings.Fields(strings.TrimSpace(string(gotBytes)))
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("Reload args = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

systemctl.go

@@ -12,8 +12,10 @@ import (
 // files, and recreate the entire dependency tree. While the daemon is being
 // reloaded, all sockets systemd listens on behalf of user configuration will
 // stay accessible.
-func DaemonReload(ctx context.Context, opts Options) error {
+//
-	return daemonReload(ctx, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func DaemonReload(ctx context.Context, opts Options, args ...string) error {
+	return daemonReload(ctx, opts, args...)
 }
 
 // Reenables one or more units.
@@ -21,8 +23,10 @@ func DaemonReload(ctx context.Context, opts Options) error {
 // This removes all symlinks to the unit files backing the specified units from
 // the unit configuration directory, then recreates the symlink to the unit again,
 // atomically. Can be used to change the symlink target.
-func Reenable(ctx context.Context, unit string, opts Options) error {
+//
-	return reenable(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Reenable(ctx context.Context, unit string, opts Options, args ...string) error {
+	return reenable(ctx, unit, opts, args...)
 }
 
 // Disables one or more units.
@@ -30,8 +34,10 @@ func Reenable(ctx context.Context, unit string, opts Options) error {
 // This removes all symlinks to the unit files backing the specified units from
 // the unit configuration directory, and hence undoes any changes made by
 // enable or link.
-func Disable(ctx context.Context, unit string, opts Options) error {
+//
-	return disable(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Disable(ctx context.Context, unit string, opts Options, args ...string) error {
+	return disable(ctx, unit, opts, args...)
 }
 
 // Enable one or more units or unit instances.
@@ -40,17 +46,20 @@ func Disable(ctx context.Context, unit string, opts Options) error {
 // the indicated unit files. After the symlinks have been created, the system
 // manager configuration is reloaded (in a way equivalent to daemon-reload),
 // in order to ensure the changes are taken into account immediately.
-func Enable(ctx context.Context, unit string, opts Options) error {
+//
-	return enable(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Enable(ctx context.Context, unit string, opts Options, args ...string) error {
+	return enable(ctx, unit, opts, args...)
 }
 
 // Check whether any of the specified units are active (i.e. running).
 //
 // Returns true if the unit is active, false if inactive or failed.
 // Also returns false in an error case.
-func IsActive(ctx context.Context, unit string, opts Options) (bool, error) {
+//
-	result, err := isActive(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
-	return result, err
+func IsActive(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
+	return isActive(ctx, unit, opts, args...)
 }
 
 // Checks whether any of the specified unit files are enabled (as with enable).
@@ -62,15 +71,17 @@ func IsActive(ctx context.Context, unit string, opts Options) (bool, error) {
 //
 // See https://www.freedesktop.org/software/systemd/man/systemctl.html#is-enabled%20UNIT%E2%80%A6
 // for more information
-func IsEnabled(ctx context.Context, unit string, opts Options) (bool, error) {
+//
-	result, err := isEnabled(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
-	return result, err
+func IsEnabled(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
+	return isEnabled(ctx, unit, opts, args...)
 }
 
 // Check whether any of the specified units are in a "failed" state.
-func IsFailed(ctx context.Context, unit string, opts Options) (bool, error) {
+//
-	result, err := isFailed(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
-	return result, err
+func IsFailed(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
+	return isFailed(ctx, unit, opts, args...)
 }
 
 // Mask one or more units, as specified on the command line. This will link
@@ -79,26 +90,40 @@ func IsFailed(ctx context.Context, unit string, opts Options) (bool, error) {
 // Notably, Mask may return ErrDoesNotExist if a unit doesn't exist, but it will
 // continue masking anyway. Calling Mask on a non-existing masked unit does not
 // return an error. Similarly, see Unmask.
-func Mask(ctx context.Context, unit string, opts Options) error {
+//
-	return mask(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Mask(ctx context.Context, unit string, opts Options, args ...string) error {
+	return mask(ctx, unit, opts, args...)
 }
 
 // Stop and then start one or more units specified on the command line.
 // If the units are not running yet, they will be started.
-func Restart(ctx context.Context, unit string, opts Options) error {
+//
-	return restart(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Restart(ctx context.Context, unit string, opts Options, args ...string) error {
+	return restart(ctx, unit, opts, args...)
+}
+
+// Reload one or more units if they support reload.
+//
+// Any additional arguments are passed directly to the systemctl command.
+func Reload(ctx context.Context, unit string, opts Options, args ...string) error {
+	return reload(ctx, unit, opts, args...)
 }
 
 // Show a selected property of a unit. Accepted properties are predefined in the
 // properties subpackage to guarantee properties are valid and assist code-completion.
-func Show(ctx context.Context, unit string, property properties.Property, opts Options) (string, error) {
+//
-	str, err := show(ctx, unit, property, opts)
+// Any additional arguments are passed directly to the systemctl command.
-	return str, err
+func Show(ctx context.Context, unit string, property properties.Property, opts Options, args ...string) (string, error) {
+	return show(ctx, unit, property, opts, args...)
 }
 
 // Start (activate) a given unit
-func Start(ctx context.Context, unit string, opts Options) error {
+//
-	return start(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Start(ctx context.Context, unit string, opts Options, args ...string) error {
+	return start(ctx, unit, opts, args...)
 }
 
 // Get back the status string which would be returned by running
@@ -106,14 +131,17 @@ func Start(ctx context.Context, unit string, opts Options) error {
 //
 // Generally, it makes more sense to programmatically retrieve the properties
 // using Show, but this command is provided for the sake of completeness
-func Status(ctx context.Context, unit string, opts Options) (string, error) {
+//
-	stat, err := status(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
-	return stat, err
+func Status(ctx context.Context, unit string, opts Options, args ...string) (string, error) {
+	return status(ctx, unit, opts, args...)
 }
 
 // Stop (deactivate) a given unit
-func Stop(ctx context.Context, unit string, opts Options) error {
+//
-	return stop(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Stop(ctx context.Context, unit string, opts Options, args ...string) error {
+	return stop(ctx, unit, opts, args...)
 }
 
 // Unmask one or more unit files, as specified on the command line.
@@ -123,6 +151,8 @@ func Stop(ctx context.Context, unit string, opts Options) error {
 // doesn't exist, but only if it's not already masked.
 // If the unit doesn't exist but it's masked anyway, no error will be
 // returned. Gross, I know. Take it up with Poettering.
-func Unmask(ctx context.Context, unit string, opts Options) error {
+//
-	return unmask(ctx, unit, opts)
+// Any additional arguments are passed directly to the systemctl command.
+func Unmask(ctx context.Context, unit string, opts Options, args ...string) error {
+	return unmask(ctx, unit, opts, args...)
 }

systemctl_darwin.go

@@ -8,58 +8,62 @@ import (
 	"github.com/taigrr/systemctl/properties"
 )
 
-func daemonReload(ctx context.Context, opts Options) error {
+func daemonReload(_ context.Context, _ Options, _ ...string) error {
 	return nil
 }
 
-func reenable(ctx context.Context, unit string, opts Options) error {
+func reenable(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func disable(ctx context.Context, unit string, opts Options) error {
+func disable(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func enable(ctx context.Context, unit string, opts Options) error {
+func enable(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func isActive(ctx context.Context, unit string, opts Options) (bool, error) {
+func isActive(_ context.Context, _ string, _ Options, _ ...string) (bool, error) {
 	return false, nil
 }
 
-func isEnabled(ctx context.Context, unit string, opts Options) (bool, error) {
+func isEnabled(_ context.Context, _ string, _ Options, _ ...string) (bool, error) {
 	return false, nil
 }
 
-func isFailed(ctx context.Context, unit string, opts Options) (bool, error) {
+func isFailed(_ context.Context, _ string, _ Options, _ ...string) (bool, error) {
 	return false, nil
 }
 
-func mask(ctx context.Context, unit string, opts Options) error {
+func mask(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func restart(ctx context.Context, unit string, opts Options) error {
+func restart(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func show(ctx context.Context, unit string, property properties.Property, opts Options) (string, error) {
+func reload(_ context.Context, _ string, _ Options, _ ...string) error {
+	return nil
+}
+
+func show(_ context.Context, _ string, _ properties.Property, _ Options, _ ...string) (string, error) {
 	return "", nil
 }
 
-func start(ctx context.Context, unit string, opts Options) error {
+func start(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func status(ctx context.Context, unit string, opts Options) (string, error) {
+func status(_ context.Context, _ string, _ Options, _ ...string) (string, error) {
 	return "", nil
 }
 
-func stop(ctx context.Context, unit string, opts Options) error {
+func stop(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }
 
-func unmask(ctx context.Context, unit string, opts Options) error {
+func unmask(_ context.Context, _ string, _ Options, _ ...string) error {
 	return nil
 }

systemctl_linux.go

@@ -9,74 +9,33 @@ import (
 	"github.com/taigrr/systemctl/properties"
 )
 
-// Reload systemd manager configuration.
+func daemonReload(ctx context.Context, opts Options, args ...string) error {
-//
+	a := prepareArgs("daemon-reload", opts, args...)
-// This will rerun all generators (see systemd. generator(7)), reload all unit
+	_, _, _, err := execute(ctx, a)
-// files, and recreate the entire dependency tree. While the daemon is being
-// reloaded, all sockets systemd listens on behalf of user configuration will
-// stay accessible.
-func daemonReload(ctx context.Context, opts Options) error {
-	args := []string{"daemon-reload", "--system"}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Reenables one or more units.
+func reenable(ctx context.Context, unit string, opts Options, args ...string) error {
-//
+	a := prepareArgs("reenable", opts, append([]string{unit}, args...)...)
-// This removes all symlinks to the unit files backing the specified units from
+	_, _, _, err := execute(ctx, a)
-// the unit configuration directory, then recreates the symlink to the unit again,
-// atomically. Can be used to change the symlink target.
-func reenable(ctx context.Context, unit string, opts Options) error {
-	args := []string{"reenable", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Disables one or more units.
+func disable(ctx context.Context, unit string, opts Options, args ...string) error {
-//
+	a := prepareArgs("disable", opts, append([]string{unit}, args...)...)
-// This removes all symlinks to the unit files backing the specified units from
+	_, _, _, err := execute(ctx, a)
-// the unit configuration directory, and hence undoes any changes made by
-// enable or link.
-func disable(ctx context.Context, unit string, opts Options) error {
-	args := []string{"disable", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Enable one or more units or unit instances.
+func enable(ctx context.Context, unit string, opts Options, args ...string) error {
-//
+	a := prepareArgs("enable", opts, append([]string{unit}, args...)...)
-// This will create a set of symlinks, as encoded in the [Install] sections of
+	_, _, _, err := execute(ctx, a)
-// the indicated unit files. After the symlinks have been created, the system
-// manager configuration is reloaded (in a way equivalent to daemon-reload),
-// in order to ensure the changes are taken into account immediately.
-func enable(ctx context.Context, unit string, opts Options) error {
-	args := []string{"enable", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Check whether any of the specified units are active (i.e. running).
+func isActive(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
-//
+	a := prepareArgs("is-active", opts, append([]string{unit}, args...)...)
-// Returns true if the unit is active, false if inactive or failed.
+	stdout, _, _, err := execute(ctx, a)
-// Also returns false in an error case.
-func isActive(ctx context.Context, unit string, opts Options) (bool, error) {
-	args := []string{"is-active", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	stdout, _, _, err := execute(ctx, args)
 	stdout = strings.TrimSuffix(stdout, "\n")
 	switch stdout {
 	case "inactive":
@@ -92,21 +51,9 @@ func isActive(ctx context.Context, unit string, opts Options) (bool, error) {
 	}
 }
 
-// Checks whether any of the specified unit files are enabled (as with enable).
+func isEnabled(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
-//
+	a := prepareArgs("is-enabled", opts, append([]string{unit}, args...)...)
-// Returns true if the unit is enabled, aliased, static, indirect, generated
+	stdout, _, _, err := execute(ctx, a)
-// or transient.
-//
-// Returns false if disabled. Also returns an error if linked, masked, or bad.
-//
-// See https://www.freedesktop.org/software/systemd/man/systemctl.html#is-enabled%20UNIT%E2%80%A6
-// for more information
-func isEnabled(ctx context.Context, unit string, opts Options) (bool, error) {
-	args := []string{"is-enabled", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	stdout, _, _, err := execute(ctx, args)
 	stdout = strings.TrimSuffix(stdout, "\n")
 	switch stdout {
 	case "enabled":
@@ -140,13 +87,9 @@ func isEnabled(ctx context.Context, unit string, opts Options) (bool, error) {
 	return false, ErrUnspecified
 }
 
-// Check whether any of the specified units are in a "failed" state.
+func isFailed(ctx context.Context, unit string, opts Options, args ...string) (bool, error) {
-func isFailed(ctx context.Context, unit string, opts Options) (bool, error) {
+	a := prepareArgs("is-failed", opts, append([]string{unit}, args...)...)
-	args := []string{"is-failed", "--system", unit}
+	stdout, _, _, err := execute(ctx, a)
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	stdout, _, _, err := execute(ctx, args)
 	stdout = strings.TrimSuffix(stdout, "\n")
 	switch stdout {
 	case "inactive":
@@ -160,91 +103,53 @@ func isFailed(ctx context.Context, unit string, opts Options) (bool, error) {
 	}
 }
 
-// Mask one or more units, as specified on the command line. This will link
+func mask(ctx context.Context, unit string, opts Options, args ...string) error {
-// these unit files to /dev/null, making it impossible to start them.
+	a := prepareArgs("mask", opts, append([]string{unit}, args...)...)
-//
+	_, _, _, err := execute(ctx, a)
-// Notably, Mask may return ErrDoesNotExist if a unit doesn't exist, but it will
-// continue masking anyway. Calling Mask on a non-existing masked unit does not
-// return an error. Similarly, see Unmask.
-func mask(ctx context.Context, unit string, opts Options) error {
-	args := []string{"mask", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Stop and then start one or more units specified on the command line.
+func restart(ctx context.Context, unit string, opts Options, args ...string) error {
-// If the units are not running yet, they will be started.
+	a := prepareArgs("restart", opts, append([]string{unit}, args...)...)
-func restart(ctx context.Context, unit string, opts Options) error {
+	_, _, _, err := execute(ctx, a)
-	args := []string{"restart", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Show a selected property of a unit. Accepted properties are predefined in the
+func reload(ctx context.Context, unit string, opts Options, args ...string) error {
-// properties subpackage to guarantee properties are valid and assist code-completion.
+	a := prepareArgs("reload", opts, append([]string{unit}, args...)...)
-func show(ctx context.Context, unit string, property properties.Property, opts Options) (string, error) {
+	_, _, _, err := execute(ctx, a)
-	args := []string{"show", "--system", unit, "--property", string(property)}
+	return err
-	if opts.UserMode {
+}
-		args[1] = "--user"
+
-	}
+func show(ctx context.Context, unit string, property properties.Property, opts Options, args ...string) (string, error) {
-	stdout, _, _, err := execute(ctx, args)
+	extra := append([]string{unit, "--property", string(property)}, args...)
+	a := prepareArgs("show", opts, extra...)
+	stdout, _, _, err := execute(ctx, a)
 	stdout = strings.TrimPrefix(stdout, string(property)+"=")
 	stdout = strings.TrimSuffix(stdout, "\n")
 	return stdout, err
 }
 
-// Start (activate) a given unit
+func start(ctx context.Context, unit string, opts Options, args ...string) error {
-func start(ctx context.Context, unit string, opts Options) error {
+	a := prepareArgs("start", opts, append([]string{unit}, args...)...)
-	args := []string{"start", "--system", unit}
+	_, _, _, err := execute(ctx, a)
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Get back the status string which would be returned by running
+func status(ctx context.Context, unit string, opts Options, args ...string) (string, error) {
-// `systemctl status [unit]`.
+	a := prepareArgs("status", opts, append([]string{unit}, args...)...)
-//
+	stdout, _, _, err := execute(ctx, a)
-// Generally, it makes more sense to programmatically retrieve the properties
-// using Show, but this command is provided for the sake of completeness
-func status(ctx context.Context, unit string, opts Options) (string, error) {
-	args := []string{"status", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	stdout, _, _, err := execute(ctx, args)
 	return stdout, err
 }
 
-// Stop (deactivate) a given unit
+func stop(ctx context.Context, unit string, opts Options, args ...string) error {
-func stop(ctx context.Context, unit string, opts Options) error {
+	a := prepareArgs("stop", opts, append([]string{unit}, args...)...)
-	args := []string{"stop", "--system", unit}
+	_, _, _, err := execute(ctx, a)
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }
 
-// Unmask one or more unit files, as specified on the command line.
+func unmask(ctx context.Context, unit string, opts Options, args ...string) error {
-// This will undo the effect of Mask.
+	a := prepareArgs("unmask", opts, append([]string{unit}, args...)...)
-//
+	_, _, _, err := execute(ctx, a)
-// In line with systemd, Unmask will return ErrDoesNotExist if the unit
-// doesn't exist, but only if it's not already masked.
-// If the unit doesn't exist but it's masked anyway, no error will be
-// returned. Gross, I know. Take it up with Poettering.
-func unmask(ctx context.Context, unit string, opts Options) error {
-	args := []string{"unmask", "--system", unit}
-	if opts.UserMode {
-		args[1] = "--user"
-	}
-	_, _, _, err := execute(ctx, args)
 	return err
 }

systemctl_test.go

@@ -290,7 +290,7 @@ func TestMask(t *testing.T) {
 		// try existing unit in user mode as user
 		{"syncthing", nil, Options{UserMode: true}, true},
 		// try nonexisting unit in system mode as user
-		{"nonexistant", ErrDoesNotExist, Options{UserMode: false}, true},
+		{"nonexistant", ErrInsufficientPermissions, Options{UserMode: false}, true},
 		// try existing unit in system mode as user
 		{"nginx", ErrInsufficientPermissions, Options{UserMode: false}, true},
 
@@ -521,7 +521,7 @@ func TestUnmask(t *testing.T) {
 		// try existing unit in user mode as user
 		{"syncthing", nil, Options{UserMode: true}, true},
 		// try nonexisting unit in system mode as user
-		{"nonexistant", ErrDoesNotExist, Options{UserMode: false}, true},
+		{"nonexistant", ErrInsufficientPermissions, Options{UserMode: false}, true},
 		// try existing unit in system mode as user
 		{"nginx", ErrInsufficientPermissions, Options{UserMode: false}, true},
 

util.go

@@ -55,16 +55,28 @@ func execute(ctx context.Context, args []string) (string, string, int, error) {
 	return output, warnings, code, err
 }
 
+// prepareArgs builds the systemctl command arguments from a base command,
+// options, and any additional arguments the caller wants to pass through.
+func prepareArgs(base string, opts Options, extra ...string) []string {
+	args := make([]string, 0, 2+len(extra))
+	args = append(args, base)
+	if opts.UserMode {
+		args = append(args, "--user")
+	} else {
+		args = append(args, "--system")
+	}
+	args = append(args, extra...)
+	return args
+}
+
 func filterErr(stderr string) error {
+	// Order matters: check higher-priority errors first.
+	// For example, `systemctl mask nginx` as a non-root user on a system
+	// without nginx prints both "does not exist, proceeding anyway" (a
+	// warning) and "Interactive authentication required" (the real error).
+	// Permission and bus errors must be checked before "does not exist" so
+	// the actual failure reason is returned.
 	switch {
-	case strings.Contains(stderr, `does not exist`):
-		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
-	case strings.Contains(stderr, `not found.`):
-		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
-	case strings.Contains(stderr, `not loaded.`):
-		return errors.Join(ErrUnitNotLoaded, fmt.Errorf("stderr: %s", stderr))
-	case strings.Contains(stderr, `No such file or directory`):
-		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
 	case strings.Contains(stderr, `Interactive authentication required`):
 		return errors.Join(ErrInsufficientPermissions, fmt.Errorf("stderr: %s", stderr))
 	case strings.Contains(stderr, `Access denied`):
@@ -73,6 +85,14 @@ func filterErr(stderr string) error {
 		return errors.Join(ErrBusFailure, fmt.Errorf("stderr: %s", stderr))
 	case strings.Contains(stderr, `is masked`):
 		return errors.Join(ErrMasked, fmt.Errorf("stderr: %s", stderr))
+	case strings.Contains(stderr, `does not exist`):
+		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
+	case strings.Contains(stderr, `not found.`):
+		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
+	case strings.Contains(stderr, `not loaded.`):
+		return errors.Join(ErrUnitNotLoaded, fmt.Errorf("stderr: %s", stderr))
+	case strings.Contains(stderr, `No such file or directory`):
+		return errors.Join(ErrDoesNotExist, fmt.Errorf("stderr: %s", stderr))
 	case strings.Contains(stderr, `Failed`):
 		return errors.Join(ErrUnspecified, fmt.Errorf("stderr: %s", stderr))
 	default:

util_test.go

@@ -0,0 +1,62 @@
+package systemctl
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestPrepareArgs(t *testing.T) {
+	tests := []struct {
+		name     string
+		base     string
+		opts     Options
+		extra    []string
+		expected []string
+	}{
+		{
+			name:     "system mode no extra",
+			base:     "start",
+			opts:     Options{},
+			extra:    nil,
+			expected: []string{"start", "--system"},
+		},
+		{
+			name:     "user mode no extra",
+			base:     "start",
+			opts:     Options{UserMode: true},
+			extra:    nil,
+			expected: []string{"start", "--user"},
+		},
+		{
+			name:     "system mode with unit",
+			base:     "start",
+			opts:     Options{},
+			extra:    []string{"nginx.service"},
+			expected: []string{"start", "--system", "nginx.service"},
+		},
+		{
+			name:     "user mode with unit and extra args",
+			base:     "restart",
+			opts:     Options{UserMode: true},
+			extra:    []string{"foo.service", "--no-block"},
+			expected: []string{"restart", "--user", "foo.service", "--no-block"},
+		},
+		{
+			name:     "daemon-reload no extra",
+			base:     "daemon-reload",
+			opts:     Options{},
+			extra:    nil,
+			expected: []string{"daemon-reload", "--system"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := prepareArgs(tt.base, tt.opts, tt.extra...)
+			if !reflect.DeepEqual(got, tt.expected) {
+				t.Errorf("prepareArgs(%q, %+v, %v) = %v, want %v",
+					tt.base, tt.opts, tt.extra, got, tt.expected)
+			}
+		})
+	}
+}