add ability to list all units

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: taigrr # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

README.md

@@ -5,7 +5,6 @@ This library aims at providing idiomatic `systemctl` bindings for go developers,
 This tool tries to take guesswork out of arbitrarily shelling out to `systemctl` by providing a structured, thoroughly-tested wrapper for the `systemctl` functions most-likely to be used in a system program.
 
 If your system isn't running (or targeting another system running) `systemctl`, this library will be of little use to you.
-In fact, if `systemctl` isn't found in the `PATH`, this library will panic.
 
 ## What is systemctl
 
@@ -18,6 +17,7 @@ In fact, if `systemctl` isn't found in the `PATH`, this library will panic.
 - [x] `systemctl daemon-reload`
 - [x] `systemctl disable`
 - [x] `systemctl enable`
+- [x] `systemctl reenable`
 - [x] `systemctl is-active`
 - [x] `systemctl is-enabled`
 - [x] `systemctl is-failed`
@@ -65,10 +65,9 @@ func main() {
     ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
     defer cancel()
     // Equivalent to `systemctl enable nginx` with a 10 second timeout
-    opts := Options{
-        usermode: false,
-    }
-    err := Enable(ctx, unit, opts)
+    opts := systemctl.Options{ UserMode: false }
+    unit := "nginx"
+    err := systemctl.Enable(ctx, unit, opts)
     if err != nil {
         log.Fatalf("unable to enable unit %s: %v", "nginx", err)
     }

errors.go

@@ -21,7 +21,6 @@ var (
 	// Masked units can only be unmasked, but something else was attempted
 	// Unmask the unit before enabling or disabling it
 	ErrMasked = errors.New("unit masked")
-	// If this error occurs, the library isn't entirely useful, as it causes a panic
 	// Make sure systemctl is in the PATH before calling again
 	ErrNotInstalled = errors.New("systemctl not in $PATH")
 	// A unit was expected to be running but was found inactive
@@ -36,5 +35,5 @@ var (
 
 	// Something in the stderr output contains the word `Failed`, but it is not a known case
 	// This is a catch-all, and if it's ever seen in the wild, please submit a PR
-	ErrUnspecified = errors.New("Unknown error, please submit an issue at github.com/taigrr/systemctl")
+	ErrUnspecified = errors.New("unknown error, please submit an issue at github.com/taigrr/systemctl")
 )

errors_test.go

@@ -2,6 +2,7 @@ package systemctl
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"reflect"
 	"runtime"
@@ -53,7 +54,6 @@ func TestErrorFuncs(t *testing.T) {
 		fName := runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name()
 		fName = strings.TrimPrefix(fName, "github.com/taigrr/")
 		t.Run(fmt.Sprintf("Errorcheck %s", fName), func(t *testing.T) {
-
 			for _, tc := range errCases {
 				t.Run(fmt.Sprintf("%s as %s", tc.unit, userString), func(t *testing.T) {
 					if (userString == "root" || userString == "system") && tc.runAsUser {
@@ -64,7 +64,7 @@ func TestErrorFuncs(t *testing.T) {
 					ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 					defer cancel()
 					err := f(ctx, tc.unit, tc.opts)
-					if err != tc.err {
+					if !errors.Is(err, tc.err) {
 						t.Errorf("error is %v, but should have been %v", err, tc.err)
 					}
 				})

go.mod

@@ -1,5 +1,3 @@
 module github.com/taigrr/systemctl
 
-go 1.16
-
-require golang.org/x/tools v0.1.1 // indirect
+go 1.12

go.sum

@@ -1,33 +0,0 @@
-github.com/yuin/goldmark v1.3.5 h1:dPmz1Snjq0kmkz159iL7S6WzdahUTHnHB5M56WFVifs=
-github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 h1:ObdrDkeb4kJdCP557AjRjq69pTHfNouLtWZG7j9rPN8=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/mod v0.4.2 h1:Gz96sIWK3OalVv/I/qNygP42zyoKp3xptRVCWRFEBvo=
-golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4 h1:4nGaVu0QrbjT/AK2PRLuQfQuh6DJve+pELhqTdAj3x0=
-golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
-golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210510120138-977fb7262007 h1:gG67DSER+11cZvqIMb8S8bt0vZtiN6xWYARwirrOSfE=
-golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.1 h1:wGiQel/hW0NnEkJUk8lbzkX2gFJU6PFxf1v5OlCfuOs=
-golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

helpers.go

@@ -2,7 +2,9 @@ package systemctl
 
 import (
 	"context"
+	"errors"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/taigrr/systemctl/properties"
@@ -13,7 +15,6 @@ const dateFormat = "Mon 2006-01-02 15:04:05 MST"
 // Get start time of a service (`systemctl show [unit] --property ExecMainStartTimestamp`) as a `Time` type
 func GetStartTime(ctx context.Context, unit string, opts Options) (time.Time, error) {
 	value, err := Show(ctx, unit, properties.ExecMainStartTimestamp, opts)
-
 	if err != nil {
 		return time.Time{}, err
 	}
@@ -53,3 +54,81 @@ func GetPID(ctx context.Context, unit string, opts Options) (int, error) {
 	}
 	return strconv.Atoi(value)
 }
+
+func GetUnits(ctx context.Context, opts Options) ([]Unit, error) {
+	args := []string{"list-units", "--all", "--no-legend", "--full", "--no-pager"}
+	if opts.UserMode {
+		args = append(args, "--user")
+	}
+	stdout, stderr, _, err := execute(ctx, args)
+	if err != nil {
+		return []Unit{}, errors.Join(err, filterErr(stderr))
+	}
+	lines := strings.Split(stdout, "\n")
+	units := []Unit{}
+	for _, line := range lines {
+		entry := strings.Fields(line)
+		if len(entry) < 4 {
+			continue
+		}
+		unit := Unit{
+			Name:        entry[0],
+			Load:        entry[1],
+			Active:      entry[2],
+			Sub:         entry[3],
+			Description: strings.Join(entry[4:], " "),
+		}
+		units = append(units, unit)
+	}
+	return units, nil
+}
+
+func GetMaskedUnits(ctx context.Context, opts Options) ([]string, error) {
+	args := []string{"list-unit-files", "--state=masked"}
+	if opts.UserMode {
+		args = append(args, "--user")
+	}
+	stdout, stderr, _, err := execute(ctx, args)
+	if err != nil {
+		return []string{}, errors.Join(err, filterErr(stderr))
+	}
+	lines := strings.Split(stdout, "\n")
+	units := []string{}
+	for _, line := range lines {
+		if !strings.Contains(line, "masked") {
+			continue
+		}
+		entry := strings.Split(line, " ")
+		if len(entry) < 3 {
+			continue
+		}
+		if entry[1] == "masked" {
+			unit := entry[0]
+			uName := strings.Split(unit, ".")
+			unit = uName[0]
+			units = append(units, unit)
+		}
+	}
+	return units, nil
+}
+
+// check if a service is masked
+func IsMasked(ctx context.Context, unit string, opts Options) (bool, error) {
+	units, err := GetMaskedUnits(ctx, opts)
+	if err != nil {
+		return false, err
+	}
+	for _, u := range units {
+		if u == unit {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// check if a service is running
+// https://unix.stackexchange.com/a/396633
+func IsRunning(ctx context.Context, unit string, opts Options) (bool, error) {
+	status, err := Show(ctx, unit, properties.SubState, opts)
+	return status == "running", err
+}

helpers_test.go

@@ -2,6 +2,7 @@ package systemctl
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"syscall"
 	"testing"
@@ -58,13 +59,13 @@ func TestGetStartTime(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			defer cancel()
 			_, err := GetStartTime(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+			if !errors.Is(err, tc.err) {
 				t.Errorf("error is %v, but should have been %v", err, tc.err)
 			}
 		})
 	}
 	// Prove start time changes after a restart
-	t.Run(fmt.Sprintf("prove start time changes"), func(t *testing.T) {
+	t.Run("prove start time changes", func(t *testing.T) {
 		if userString != "root" && userString != "system" {
 			t.Skip("skipping superuser test while running as user")
 		}
@@ -90,15 +91,16 @@ func TestGetStartTime(t *testing.T) {
 			t.Errorf("Expected start diff to be positive, but got: %d", int(diff))
 		}
 	})
-
 }
+
 func TestGetNumRestarts(t *testing.T) {
-	testCases := []struct {
+	type testCase struct {
 		unit      string
 		err       error
 		opts      Options
 		runAsUser bool
-	}{
+	}
+	testCases := []testCase{
 		// Run these tests only as a user
 
 		// try nonexistant unit in user mode as user
@@ -118,6 +120,7 @@ func TestGetNumRestarts(t *testing.T) {
 		{"nginx", nil, Options{UserMode: false}, false},
 	}
 	for _, tc := range testCases {
+		func(tc testCase) {
 			t.Run(fmt.Sprintf("%s as %s", tc.unit, userString), func(t *testing.T) {
 				t.Parallel()
 				if (userString == "root" || userString == "system") && tc.runAsUser {
@@ -128,13 +131,14 @@ func TestGetNumRestarts(t *testing.T) {
 				ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 				defer cancel()
 				_, err := GetNumRestarts(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+				if !errors.Is(err, tc.err) {
 					t.Errorf("error is %v, but should have been %v", err, tc.err)
 				}
 			})
+		}(tc)
 	}
 	// Prove restart count increases by one after a restart
-	t.Run(fmt.Sprintf("prove restart count increases by one after a restart"), func(t *testing.T) {
+	t.Run("prove restart count increases by one after a restart", func(t *testing.T) {
 		if testing.Short() {
 			t.Skip("skipping in short mode")
 		}
@@ -154,9 +158,9 @@ func TestGetNumRestarts(t *testing.T) {
 		}
 		syscall.Kill(pid, syscall.SIGKILL)
 		for {
-			running, err := IsActive(ctx, "nginx", Options{UserMode: false})
-			if err != nil {
-				t.Errorf("error asserting nginx is up: %v", err)
+			running, errIsActive := IsActive(ctx, "nginx", Options{UserMode: false})
+			if errIsActive != nil {
+				t.Errorf("error asserting nginx is up: %v", errIsActive)
 				break
 			} else if running {
 				break
@@ -170,16 +174,16 @@ func TestGetNumRestarts(t *testing.T) {
 			t.Errorf("Expected restart count to differ by one, but difference was: %d", secondRestarts-restarts)
 		}
 	})
-
 }
 
 func TestGetMemoryUsage(t *testing.T) {
-	testCases := []struct {
+	type testCase struct {
 		unit      string
 		err       error
 		opts      Options
 		runAsUser bool
-	}{
+	}
+	testCases := []testCase{
 		// Run these tests only as a user
 
 		// try nonexistant unit in user mode as user
@@ -199,6 +203,7 @@ func TestGetMemoryUsage(t *testing.T) {
 		{"nginx", nil, Options{UserMode: false}, false},
 	}
 	for _, tc := range testCases {
+		func(tc testCase) {
 			t.Run(fmt.Sprintf("%s as %s", tc.unit, userString), func(t *testing.T) {
 				t.Parallel()
 				if (userString == "root" || userString == "system") && tc.runAsUser {
@@ -209,13 +214,14 @@ func TestGetMemoryUsage(t *testing.T) {
 				ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 				defer cancel()
 				_, err := GetMemoryUsage(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+				if !errors.Is(err, tc.err) {
 					t.Errorf("error is %v, but should have been %v", err, tc.err)
 				}
 			})
+		}(tc)
 	}
 	// Prove memory usage values change across services
-	t.Run(fmt.Sprintf("prove memory usage values change across services"), func(t *testing.T) {
+	t.Run("prove memory usage values change across services", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
 		bytes, err := GetMemoryUsage(ctx, "nginx", Options{UserMode: false})
@@ -230,15 +236,65 @@ func TestGetMemoryUsage(t *testing.T) {
 			t.Errorf("Expected memory usage between nginx and user.slice to differ, but both were: %d", bytes)
 		}
 	})
-
 }
+
+func TestGetUnits(t *testing.T) {
+	type testCase struct {
+		err       error
+		runAsUser bool
+		opts      Options
+	}
+	testCases := []testCase{{
+		// Run these tests only as a user
+		runAsUser: true,
+		opts:      Options{UserMode: true},
+		err:       nil,
+	}}
+	for _, tc := range testCases {
+		t.Run(fmt.Sprintf("as %s", userString), func(t *testing.T) {
+			if (userString == "root" || userString == "system") && tc.runAsUser {
+				t.Skip("skipping user test while running as superuser")
+			} else if (userString != "root" && userString != "system") && !tc.runAsUser {
+				t.Skip("skipping superuser test while running as user")
+			}
+			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+			defer cancel()
+			units, err := GetUnits(ctx, tc.opts)
+			if !errors.Is(err, tc.err) {
+				t.Errorf("error is %v, but should have been %v", err, tc.err)
+			}
+			if len(units) == 0 {
+				t.Errorf("Expected at least one unit, but got none")
+			}
+			unit := units[0]
+			if unit.Name == "" {
+				t.Errorf("Expected unit name to be non-empty, but got empty")
+			}
+			if unit.Load == "" {
+				t.Errorf("Expected unit load state to be non-empty, but got empty")
+			}
+			if unit.Active == "" {
+				t.Errorf("Expected unit active state to be non-empty, but got empty")
+			}
+			if unit.Sub == "" {
+				t.Errorf("Expected unit sub state to be non-empty, but got empty")
+			}
+			if unit.Description == "" {
+				t.Errorf("Expected unit description to be non-empty, but got empty")
+			}
+		})
+	}
+}
+
 func TestGetPID(t *testing.T) {
-	testCases := []struct {
+	type testCase struct {
 		unit      string
 		err       error
 		opts      Options
 		runAsUser bool
-	}{
+	}
+
+	testCases := []testCase{
 		// Run these tests only as a user
 
 		// try nonexistant unit in user mode as user
@@ -258,6 +314,7 @@ func TestGetPID(t *testing.T) {
 		{"nginx", nil, Options{UserMode: false}, false},
 	}
 	for _, tc := range testCases {
+		func(tc testCase) {
 			t.Run(fmt.Sprintf("%s as %s", tc.unit, userString), func(t *testing.T) {
 				t.Parallel()
 				if (userString == "root" || userString == "system") && tc.runAsUser {
@@ -268,12 +325,13 @@ func TestGetPID(t *testing.T) {
 				ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 				defer cancel()
 				_, err := GetPID(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+				if !errors.Is(err, tc.err) {
 					t.Errorf("error is %v, but should have been %v", err, tc.err)
 				}
 			})
+		}(tc)
 	}
-	t.Run(fmt.Sprintf("prove pid changes"), func(t *testing.T) {
+	t.Run("prove pid changes", func(t *testing.T) {
 		if testing.Short() {
 			t.Skip("skipping in short mode")
 		}
@@ -296,7 +354,5 @@ func TestGetPID(t *testing.T) {
 		if pid == secondPid {
 			t.Errorf("Expected pid != secondPid, but both were: %d", pid)
 		}
-
 	})
-
 }

structs.go

@@ -3,3 +3,11 @@ package systemctl
 type Options struct {
 	UserMode bool
 }
+
+type Unit struct {
+	Name        string
+	Load        string
+	Active      string
+	Sub         string
+	Description string
+}

systemctl.go

@@ -15,7 +15,21 @@ import (
 // reloaded, all sockets systemd listens on behalf of user configuration will
 // stay accessible.
 func DaemonReload(ctx context.Context, opts Options) error {
-	var args = []string{"daemon-reload", "--system"}
+	args := []string{"daemon-reload", "--system"}
+	if opts.UserMode {
+		args[1] = "--user"
+	}
+	_, _, _, err := execute(ctx, args)
+	return err
+}
+
+// Reenables one or more units.
+//
+// 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 {
+	args := []string{"reenable", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -29,7 +43,7 @@ func DaemonReload(ctx context.Context, opts Options) error {
 // the unit configuration directory, and hence undoes any changes made by
 // enable or link.
 func Disable(ctx context.Context, unit string, opts Options) error {
-	var args = []string{"disable", "--system", unit}
+	args := []string{"disable", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -44,7 +58,7 @@ func Disable(ctx context.Context, unit string, opts Options) error {
 // 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 {
-	var args = []string{"enable", "--system", unit}
+	args := []string{"enable", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -57,7 +71,7 @@ func Enable(ctx context.Context, unit string, opts Options) error {
 // 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) {
-	var args = []string{"is-active", "--system", unit}
+	args := []string{"is-active", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -87,7 +101,7 @@ 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) {
-	var args = []string{"is-enabled", "--system", unit}
+	args := []string{"is-enabled", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -127,7 +141,7 @@ func IsEnabled(ctx context.Context, unit string, opts Options) (bool, error) {
 
 // Check whether any of the specified units are in a "failed" state.
 func IsFailed(ctx context.Context, unit string, opts Options) (bool, error) {
-	var args = []string{"is-failed", "--system", unit}
+	args := []string{"is-failed", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -149,7 +163,7 @@ func IsFailed(ctx context.Context, unit string, opts Options) (bool, error) {
 // 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 {
-	var args = []string{"mask", "--system", unit}
+	args := []string{"mask", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -160,7 +174,7 @@ func Mask(ctx context.Context, unit string, opts Options) error {
 // 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 {
-	var args = []string{"restart", "--system", unit}
+	args := []string{"restart", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -171,7 +185,7 @@ func Restart(ctx context.Context, unit string, opts Options) error {
 // 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) {
-	var args = []string{"show", "--system", unit, "--property", string(property)}
+	args := []string{"show", "--system", unit, "--property", string(property)}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -183,7 +197,7 @@ func Show(ctx context.Context, unit string, property properties.Property, opts O
 
 // Start (activate) a given unit
 func Start(ctx context.Context, unit string, opts Options) error {
-	var args = []string{"start", "--system", unit}
+	args := []string{"start", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -197,7 +211,7 @@ func Start(ctx context.Context, unit string, opts Options) error {
 // Generally, it makes more sense to programatically 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) {
-	var args = []string{"status", "--system", unit}
+	args := []string{"status", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -207,7 +221,7 @@ func Status(ctx context.Context, unit string, opts Options) (string, error) {
 
 // Stop (deactivate) a given unit
 func Stop(ctx context.Context, unit string, opts Options) error {
-	var args = []string{"stop", "--system", unit}
+	args := []string{"stop", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}
@@ -223,7 +237,7 @@ func Stop(ctx context.Context, unit string, opts Options) error {
 // 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 {
-	var args = []string{"unmask", "--system", unit}
+	args := []string{"unmask", "--system", unit}
 	if opts.UserMode {
 		args[1] = "--user"
 	}

systemctl_test.go

@@ -2,6 +2,7 @@ package systemctl
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"os/user"
@@ -38,9 +39,9 @@ func TestMain(m *testing.M) {
 	}
 	os.Exit(retCode)
 }
+
 func TestDaemonReload(t *testing.T) {
 	testCases := []struct {
-		unit      string
 		err       error
 		opts      Options
 		runAsUser bool
@@ -48,22 +49,26 @@ func TestDaemonReload(t *testing.T) {
 		/* Run these tests only as a user */
 
 		// fail to reload system daemon as user
-		{"", ErrInsufficientPermissions, Options{UserMode: false}, true},
+		{ErrInsufficientPermissions, Options{UserMode: false}, true},
 		// reload user's scope daemon
-		{"", nil, Options{UserMode: true}, true},
+		{nil, Options{UserMode: true}, true},
 		/* End user tests*/
 
 		/* Run these tests only as a superuser */
 
 		// succeed to reload daemon
-		{"", nil, Options{UserMode: false}, false},
+		{nil, Options{UserMode: false}, false},
 		// fail to connect to user bus as system
-		{"", ErrBusFailure, Options{UserMode: true}, false},
+		{ErrBusFailure, Options{UserMode: true}, false},
 
 		/* End superuser tests*/
 	}
 	for _, tc := range testCases {
-		t.Run(fmt.Sprintf("%s as %s", tc.unit, userString), func(t *testing.T) {
+		mode := "user"
+		if tc.opts.UserMode == false {
+			mode = "system"
+		}
+		t.Run(fmt.Sprintf("DaemonReload as %s, %s mode", userString, mode), func(t *testing.T) {
 			if (userString == "root" || userString == "system") && tc.runAsUser {
 				t.Skip("skipping user test while running as superuser")
 			} else if (userString != "root" && userString != "system") && !tc.runAsUser {
@@ -72,14 +77,14 @@ func TestDaemonReload(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			defer cancel()
 			err := DaemonReload(ctx, tc.opts)
-			if err != tc.err {
+			if !errors.Is(err, tc.err) {
 				t.Errorf("error is %v, but should have been %v", err, tc.err)
 			}
 		})
 	}
 }
+
 func TestDisable(t *testing.T) {
-	t.Run(fmt.Sprintf(""), func(t *testing.T) {
 	if userString != "root" && userString != "system" {
 		t.Skip("skipping superuser test while running as user")
 	}
@@ -92,7 +97,7 @@ func TestDisable(t *testing.T) {
 		t.Errorf("Unable to mask %s", unit)
 	}
 	err = Disable(ctx, unit, Options{UserMode: false})
-		if err != ErrMasked {
+	if !errors.Is(err, ErrMasked) {
 		Unmask(ctx, unit, Options{UserMode: false})
 		t.Errorf("error is %v, but should have been %v", err, ErrMasked)
 	}
@@ -100,12 +105,32 @@ func TestDisable(t *testing.T) {
 	if err != nil {
 		t.Errorf("Unable to unmask %s", unit)
 	}
-	})
-
 }
-func TestEnable(t *testing.T) {
 
-	t.Run(fmt.Sprintf(""), func(t *testing.T) {
+func TestReenable(t *testing.T) {
+	if userString != "root" && userString != "system" {
+		t.Skip("skipping superuser test while running as user")
+	}
+	unit := "nginx"
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	err := Mask(ctx, unit, Options{UserMode: false})
+	if err != nil {
+		Unmask(ctx, unit, Options{UserMode: false})
+		t.Errorf("Unable to mask %s", unit)
+	}
+	err = Reenable(ctx, unit, Options{UserMode: false})
+	if !errors.Is(err, ErrMasked) {
+		Unmask(ctx, unit, Options{UserMode: false})
+		t.Errorf("error is %v, but should have been %v", err, ErrMasked)
+	}
+	err = Unmask(ctx, unit, Options{UserMode: false})
+	if err != nil {
+		t.Errorf("Unable to unmask %s", unit)
+	}
+}
+
+func TestEnable(t *testing.T) {
 	if userString != "root" && userString != "system" {
 		t.Skip("skipping superuser test while running as user")
 	}
@@ -118,7 +143,7 @@ func TestEnable(t *testing.T) {
 		t.Errorf("Unable to mask %s", unit)
 	}
 	err = Enable(ctx, unit, Options{UserMode: false})
-		if err != ErrMasked {
+	if !errors.Is(err, ErrMasked) {
 		Unmask(ctx, unit, Options{UserMode: false})
 		t.Errorf("error is %v, but should have been %v", err, ErrMasked)
 	}
@@ -126,25 +151,24 @@ func TestEnable(t *testing.T) {
 	if err != nil {
 		t.Errorf("Unable to unmask %s", unit)
 	}
-	})
-
 }
+
 func ExampleEnable() {
 	unit := "syncthing"
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
 	err := Enable(ctx, unit, Options{UserMode: true})
-	switch err {
-	case ErrMasked:
+	switch {
+	case errors.Is(err, ErrMasked):
 		fmt.Printf("%s is masked, unmask it before enabling\n", unit)
-	case ErrDoesNotExist:
+	case errors.Is(err, ErrDoesNotExist):
 		fmt.Printf("%s does not exist\n", unit)
-	case ErrInsufficientPermissions:
+	case errors.Is(err, ErrInsufficientPermissions):
 		fmt.Printf("permission to enable %s denied\n", unit)
-	case ErrBusFailure:
+	case errors.Is(err, ErrBusFailure):
 		fmt.Printf("Cannot communicate with the bus\n")
-	case nil:
+	case err == nil:
 		fmt.Printf("%s enabled successfully\n", unit)
 	default:
 		fmt.Printf("Error: %v", err)
@@ -153,7 +177,7 @@ func ExampleEnable() {
 
 func TestIsActive(t *testing.T) {
 	unit := "nginx"
-	t.Run(fmt.Sprintf("check active"), func(t *testing.T) {
+	t.Run("check active", func(t *testing.T) {
 		if testing.Short() {
 			t.Skip("skipping in short mode")
 		}
@@ -169,10 +193,10 @@ func TestIsActive(t *testing.T) {
 		time.Sleep(time.Second)
 		isActive, err := IsActive(ctx, unit, Options{UserMode: false})
 		if !isActive {
-			t.Errorf("IsActive didn't return true for %s", unit)
+			t.Errorf("IsActive didn't return true for %s: %v", unit, err)
 		}
 	})
-	t.Run(fmt.Sprintf("check masked"), func(t *testing.T) {
+	t.Run("check masked", func(t *testing.T) {
 		if userString != "root" && userString != "system" {
 			t.Skip("skipping superuser test while running as user")
 		}
@@ -188,7 +212,7 @@ func TestIsActive(t *testing.T) {
 		}
 		Unmask(ctx, unit, Options{UserMode: false})
 	})
-	t.Run(fmt.Sprintf("check masked"), func(t *testing.T) {
+	t.Run("check masked", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
 		_, err := IsActive(ctx, "nonexistant", Options{UserMode: false})
@@ -196,7 +220,6 @@ func TestIsActive(t *testing.T) {
 			t.Errorf("error is %v, but should have been %v", err, ErrDoesNotExist)
 		}
 	})
-
 }
 
 func TestIsEnabled(t *testing.T) {
@@ -206,7 +229,7 @@ func TestIsEnabled(t *testing.T) {
 		userMode = true
 		unit = "syncthing"
 	}
-	t.Run(fmt.Sprintf("check enabled"), func(t *testing.T) {
+	t.Run("check enabled", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 		defer cancel()
 		err := Enable(ctx, unit, Options{UserMode: userMode})
@@ -215,10 +238,10 @@ func TestIsEnabled(t *testing.T) {
 		}
 		isEnabled, err := IsEnabled(ctx, unit, Options{UserMode: userMode})
 		if !isEnabled {
-			t.Errorf("IsEnabled didn't return true for %s", unit)
+			t.Errorf("IsEnabled didn't return true for %s: %v", unit, err)
 		}
 	})
-	t.Run(fmt.Sprintf("check disabled"), func(t *testing.T) {
+	t.Run("check disabled", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
 		err := Disable(ctx, unit, Options{UserMode: userMode})
@@ -234,7 +257,7 @@ func TestIsEnabled(t *testing.T) {
 		}
 		Enable(ctx, unit, Options{UserMode: false})
 	})
-	t.Run(fmt.Sprintf("check masked"), func(t *testing.T) {
+	t.Run("check masked", func(t *testing.T) {
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
 		err := Mask(ctx, unit, Options{UserMode: userMode})
@@ -251,7 +274,6 @@ func TestIsEnabled(t *testing.T) {
 		Unmask(ctx, unit, Options{UserMode: userMode})
 		Enable(ctx, unit, Options{UserMode: userMode})
 	})
-
 }
 
 func TestMask(t *testing.T) {
@@ -296,13 +318,13 @@ func TestMask(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			defer cancel()
 			err := Mask(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+			if !errors.Is(err, tc.err) {
 				t.Errorf("error is %v, but should have been %v", err, tc.err)
 			}
 			Unmask(ctx, tc.unit, tc.opts)
 		})
 	}
-	t.Run(fmt.Sprintf("test double masking existing"), func(t *testing.T) {
+	t.Run("test double masking existing", func(t *testing.T) {
 		unit := "nginx"
 		userMode := false
 		if userString != "root" && userString != "system" {
@@ -321,19 +343,16 @@ func TestMask(t *testing.T) {
 			t.Errorf("error on second masking is %v, but should have been %v", err, nil)
 		}
 		Unmask(ctx, unit, opts)
-
 	})
-	t.Run(fmt.Sprintf("test double masking nonexisting"), func(t *testing.T) {
+	t.Run("test double masking nonexisting", func(t *testing.T) {
 		unit := "nonexistant"
-		userMode := false
-		if userString != "root" && userString != "system" {
-			userMode = true
-		}
+		userMode := userString != "root" && userString != "system"
+
 		opts := Options{UserMode: userMode}
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
 		err := Mask(ctx, unit, opts)
-		if err != ErrDoesNotExist {
+		if !errors.Is(err, ErrDoesNotExist) {
 			t.Errorf("error on initial masking is %v, but should have been %v", err, ErrDoesNotExist)
 		}
 		err = Mask(ctx, unit, opts)
@@ -342,7 +361,6 @@ func TestMask(t *testing.T) {
 		}
 		Unmask(ctx, unit, opts)
 	})
-
 }
 
 func TestRestart(t *testing.T) {
@@ -366,9 +384,9 @@ func TestRestart(t *testing.T) {
 	}
 	syscall.Kill(pid, syscall.SIGKILL)
 	for {
-		running, err := IsActive(ctx, unit, opts)
-		if err != nil {
-			t.Errorf("error asserting %s is up: %v", unit, err)
+		running, errIsActive := IsActive(ctx, unit, opts)
+		if errIsActive != nil {
+			t.Errorf("error asserting %s is up: %v", unit, errIsActive)
 			break
 		} else if running {
 			break
@@ -381,7 +399,6 @@ func TestRestart(t *testing.T) {
 	if restarts+1 != secondRestarts {
 		t.Errorf("Expected restart count to differ by one, but difference was: %d", secondRestarts-restarts)
 	}
-
 }
 
 // Runs through all defined Properties in parallel and checks for error cases
@@ -394,6 +411,7 @@ func TestShow(t *testing.T) {
 		UserMode: false,
 	}
 	for _, x := range properties.Properties {
+		func(x properties.Property) {
 			t.Run(fmt.Sprintf("show property %s", string(x)), func(t *testing.T) {
 				ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 				defer cancel()
@@ -403,6 +421,7 @@ func TestShow(t *testing.T) {
 					t.Errorf("error is %v, but should have been %v", err, nil)
 				}
 			})
+		}(x)
 	}
 }
 
@@ -439,7 +458,6 @@ func TestStart(t *testing.T) {
 			break
 		}
 	}
-
 }
 
 func TestStatus(t *testing.T) {
@@ -452,7 +470,6 @@ func TestStatus(t *testing.T) {
 	if err != nil {
 		t.Errorf("error: %v", err)
 	}
-
 }
 
 func TestStop(t *testing.T) {
@@ -488,7 +505,6 @@ func TestStop(t *testing.T) {
 			break
 		}
 	}
-
 }
 
 func TestUnmask(t *testing.T) {
@@ -533,13 +549,13 @@ func TestUnmask(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			defer cancel()
 			err := Mask(ctx, tc.unit, tc.opts)
-			if err != tc.err {
+			if !errors.Is(err, tc.err) {
 				t.Errorf("error is %v, but should have been %v", err, tc.err)
 			}
 			Unmask(ctx, tc.unit, tc.opts)
 		})
 	}
-	t.Run(fmt.Sprintf("test double unmasking existing"), func(t *testing.T) {
+	t.Run("test double unmasking existing", func(t *testing.T) {
 		unit := "nginx"
 		userMode := false
 		if userString != "root" && userString != "system" {
@@ -558,14 +574,11 @@ func TestUnmask(t *testing.T) {
 			t.Errorf("error on second unmasking is %v, but should have been %v", err, nil)
 		}
 		Unmask(ctx, unit, opts)
-
 	})
-	t.Run(fmt.Sprintf("test double unmasking nonexisting"), func(t *testing.T) {
+	t.Run("test double unmasking nonexisting", func(t *testing.T) {
 		unit := "nonexistant"
-		userMode := false
-		if userString != "root" && userString != "system" {
-			userMode = true
-		}
+		userMode := userString != "root" && userString != "system"
+
 		opts := Options{UserMode: userMode}
 		ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 		defer cancel()
@@ -575,9 +588,8 @@ func TestUnmask(t *testing.T) {
 			t.Errorf("error on initial unmasking is %v, but should have been %v", err, nil)
 		}
 		err = Unmask(ctx, unit, opts)
-		if err != ErrDoesNotExist {
+		if !errors.Is(err, ErrDoesNotExist) {
 			t.Errorf("error on second unmasking is %v, but should have been %v", err, ErrDoesNotExist)
 		}
 	})
-
 }

util.go

@@ -3,9 +3,10 @@ package systemctl
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"os/exec"
-	"regexp"
+	"strings"
 )
 
 var systemctl string
@@ -13,10 +14,7 @@ var systemctl string
 const killed = 130
 
 func init() {
-	path, err := exec.LookPath("systemctl")
-	if err != nil {
-		panic(ErrNotInstalled)
-	}
+	path, _ := exec.LookPath("systemctl")
 	systemctl = path
 }
 
@@ -30,6 +28,9 @@ func execute(ctx context.Context, args []string) (string, string, int, error) {
 		warnings string
 	)
 
+	if systemctl == "" {
+		return "", "", 1, ErrNotInstalled
+	}
 	cmd := exec.CommandContext(ctx, systemctl, args...)
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
@@ -50,32 +51,26 @@ func execute(ctx context.Context, args []string) (string, string, int, error) {
 }
 
 func filterErr(stderr string) error {
-	if matched, _ := regexp.MatchString(`does not exist`, stderr); matched {
-		return ErrDoesNotExist
-	}
-	if matched, _ := regexp.MatchString(`not found.`, stderr); matched {
-		return ErrDoesNotExist
-	}
-	if matched, _ := regexp.MatchString(`not loaded.`, stderr); matched {
-		return ErrUnitNotLoaded
-	}
-	if matched, _ := regexp.MatchString(`No such file or directory`, stderr); matched {
-		return ErrDoesNotExist
-	}
-	if matched, _ := regexp.MatchString(`Interactive authentication required`, stderr); matched {
-		return ErrInsufficientPermissions
-	}
-	if matched, _ := regexp.MatchString(`Access denied`, stderr); matched {
-		return ErrInsufficientPermissions
-	}
-	if matched, _ := regexp.MatchString(`DBUS_SESSION_BUS_ADDRESS`, stderr); matched {
-		return ErrBusFailure
-	}
-	if matched, _ := regexp.MatchString(`is masked`, stderr); matched {
-		return ErrMasked
-	}
-	if matched, _ := regexp.MatchString(`Failed`, stderr); matched {
-		return ErrUnspecified
-	}
+	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`):
+		return errors.Join(ErrInsufficientPermissions, fmt.Errorf("stderr: %s", stderr))
+	case strings.Contains(stderr, `DBUS_SESSION_BUS_ADDRESS`):
+		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, `Failed`):
+		return errors.Join(ErrUnspecified, fmt.Errorf("stderr: %s", stderr))
+	default:
 		return nil
 	}
+}