diff --git a/cmd/mailfull/command/aliasdomainadd.go b/cmd/mailfull/cmd_aliasdomainadd.go
similarity index 67%
rename from cmd/mailfull/command/aliasdomainadd.go
rename to cmd/mailfull/cmd_aliasdomainadd.go
index 2eb90d5..1e68ad8 100644
--- a/cmd/mailfull/command/aliasdomainadd.go
+++ b/cmd/mailfull/cmd_aliasdomainadd.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasDomainAddCommand represents a AliasDomainAddCommand.
-type AliasDomainAddCommand struct {
-	Meta
+// CmdAliasDomainAdd represents a CmdAliasDomainAdd.
+type CmdAliasDomainAdd struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasDomainAddCommand) Synopsis() string {
+func (c *CmdAliasDomainAdd) Synopsis() string {
 	return "Create a new aliasdomain."
 }
 
 // Help returns long-form help text.
-func (c *AliasDomainAddCommand) Help() string {
+func (c *CmdAliasDomainAdd) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain target
@@ -42,7 +43,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasDomainAddCommand) Run(args []string) int {
+func (c *CmdAliasDomainAdd) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -59,18 +60,18 @@ func (c *AliasDomainAddCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	aliasDomain, err := mailfull.NewAliasDomain(aliasDomainName, targetDomainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.AliasDomainCreate(aliasDomain); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -80,13 +81,13 @@ func (c *AliasDomainAddCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/aliasdomaindel.go b/cmd/mailfull/cmd_aliasdomaindel.go
similarity index 66%
rename from cmd/mailfull/command/aliasdomaindel.go
rename to cmd/mailfull/cmd_aliasdomaindel.go
index 1310f93..aab3df5 100644
--- a/cmd/mailfull/command/aliasdomaindel.go
+++ b/cmd/mailfull/cmd_aliasdomaindel.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasDomainDelCommand represents a AliasDomainDelCommand.
-type AliasDomainDelCommand struct {
-	Meta
+// CmdAliasDomainDel represents a CmdAliasDomainDel.
+type CmdAliasDomainDel struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasDomainDelCommand) Synopsis() string {
+func (c *CmdAliasDomainDel) Synopsis() string {
 	return "Delete a aliasdomain."
 }
 
 // Help returns long-form help text.
-func (c *AliasDomainDelCommand) Help() string {
+func (c *CmdAliasDomainDel) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasDomainDelCommand) Run(args []string) int {
+func (c *CmdAliasDomainDel) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,12 +57,12 @@ func (c *AliasDomainDelCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.AliasDomainRemove(aliasDomainName); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -71,13 +72,13 @@ func (c *AliasDomainDelCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/aliasdomains.go b/cmd/mailfull/cmd_aliasdomains.go
similarity index 71%
rename from cmd/mailfull/command/aliasdomains.go
rename to cmd/mailfull/cmd_aliasdomains.go
index 62cbac7..0a8bf2c 100644
--- a/cmd/mailfull/command/aliasdomains.go
+++ b/cmd/mailfull/cmd_aliasdomains.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"sort"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasDomainsCommand represents a AliasDomainsCommand.
-type AliasDomainsCommand struct {
-	Meta
+// CmdAliasDomains represents a CmdAliasDomains.
+type CmdAliasDomains struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasDomainsCommand) Synopsis() string {
+func (c *CmdAliasDomains) Synopsis() string {
 	return "Show aliasdomains."
 }
 
 // Help returns long-form help text.
-func (c *AliasDomainsCommand) Help() string {
+func (c *CmdAliasDomains) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [domain]
@@ -37,7 +38,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasDomainsCommand) Run(args []string) int {
+func (c *CmdAliasDomains) Run(args []string) int {
 	if len(args) > 1 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -50,13 +51,13 @@ func (c *AliasDomainsCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	aliasDomains, err := repo.AliasDomains()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	sort.Sort(mailfull.AliasDomainSlice(aliasDomains))
diff --git a/cmd/mailfull/command/aliasuseradd.go b/cmd/mailfull/cmd_aliasuseradd.go
similarity index 71%
rename from cmd/mailfull/command/aliasuseradd.go
rename to cmd/mailfull/cmd_aliasuseradd.go
index 9d6ee93..8760eb6 100644
--- a/cmd/mailfull/command/aliasuseradd.go
+++ b/cmd/mailfull/cmd_aliasuseradd.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasUserAddCommand represents a AliasUserAddCommand.
-type AliasUserAddCommand struct {
-	Meta
+// CmdAliasUserAdd represents a CmdAliasUserAdd.
+type CmdAliasUserAdd struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasUserAddCommand) Synopsis() string {
+func (c *CmdAliasUserAdd) Synopsis() string {
 	return "Create a new aliasuser."
 }
 
 // Help returns long-form help text.
-func (c *AliasUserAddCommand) Help() string {
+func (c *CmdAliasUserAdd) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address target [target...]
@@ -43,7 +44,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasUserAddCommand) Run(args []string) int {
+func (c *CmdAliasUserAdd) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -68,18 +69,18 @@ func (c *AliasUserAddCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	aliasUser, err := mailfull.NewAliasUser(aliasUserName, targets)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.AliasUserCreate(domainName, aliasUser); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -89,13 +90,13 @@ func (c *AliasUserAddCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/aliasuserdel.go b/cmd/mailfull/cmd_aliasuserdel.go
similarity index 70%
rename from cmd/mailfull/command/aliasuserdel.go
rename to cmd/mailfull/cmd_aliasuserdel.go
index 0eb5d12..6c86072 100644
--- a/cmd/mailfull/command/aliasuserdel.go
+++ b/cmd/mailfull/cmd_aliasuserdel.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasUserDelCommand represents a AliasUserDelCommand.
-type AliasUserDelCommand struct {
-	Meta
+// CmdAliasUserDel represents a CmdAliasUserDel.
+type CmdAliasUserDel struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasUserDelCommand) Synopsis() string {
+func (c *CmdAliasUserDel) Synopsis() string {
 	return "Delete a aliasuser."
 }
 
 // Help returns long-form help text.
-func (c *AliasUserDelCommand) Help() string {
+func (c *CmdAliasUserDel) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address
@@ -41,7 +42,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasUserDelCommand) Run(args []string) int {
+func (c *CmdAliasUserDel) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -64,12 +65,12 @@ func (c *AliasUserDelCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.AliasUserRemove(domainName, aliasUserName); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -79,13 +80,13 @@ func (c *AliasUserDelCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/aliasusermod.go b/cmd/mailfull/cmd_aliasusermod.go
similarity index 68%
rename from cmd/mailfull/command/aliasusermod.go
rename to cmd/mailfull/cmd_aliasusermod.go
index 459cd67..213b683 100644
--- a/cmd/mailfull/command/aliasusermod.go
+++ b/cmd/mailfull/cmd_aliasusermod.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
-	mailfull "github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasUserModCommand represents a AliasUserModCommand.
-type AliasUserModCommand struct {
-	Meta
+// CmdAliasUserMod represents a CmdAliasUserMod.
+type CmdAliasUserMod struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasUserModCommand) Synopsis() string {
+func (c *CmdAliasUserMod) Synopsis() string {
 	return "Modify a aliasuser."
 }
 
 // Help returns long-form help text.
-func (c *AliasUserModCommand) Help() string {
+func (c *CmdAliasUserMod) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address target [target...]
@@ -43,7 +44,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasUserModCommand) Run(args []string) int {
+func (c *CmdAliasUserMod) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -68,27 +69,27 @@ func (c *AliasUserModCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	aliasUser, err := repo.AliasUser(domainName, aliasUserName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	if aliasUser == nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", mailfull.ErrAliasUserNotExist)
+		c.Meta.Errorf("%v\n", mailfull.ErrAliasUserNotExist)
 		return 1
 	}
 
 	if err := aliasUser.SetTargets(targets); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.AliasUserUpdate(domainName, aliasUser); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -98,13 +99,13 @@ func (c *AliasUserModCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/aliasusers.go b/cmd/mailfull/cmd_aliasusers.go
similarity index 70%
rename from cmd/mailfull/command/aliasusers.go
rename to cmd/mailfull/cmd_aliasusers.go
index 036b23a..4469f09 100644
--- a/cmd/mailfull/command/aliasusers.go
+++ b/cmd/mailfull/cmd_aliasusers.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"sort"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// AliasUsersCommand represents a AliasUsersCommand.
-type AliasUsersCommand struct {
-	Meta
+// CmdAliasUsers represents a CmdAliasUsers.
+type CmdAliasUsers struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *AliasUsersCommand) Synopsis() string {
+func (c *CmdAliasUsers) Synopsis() string {
 	return "Show aliasusers."
 }
 
 // Help returns long-form help text.
-func (c *AliasUsersCommand) Help() string {
+func (c *CmdAliasUsers) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s domain
@@ -37,7 +38,7 @@ Required Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *AliasUsersCommand) Run(args []string) int {
+func (c *CmdAliasUsers) Run(args []string) int {
 	if len(args) != 1 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -47,13 +48,13 @@ func (c *AliasUsersCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	aliasUsers, err := repo.AliasUsers(targetDomainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	sort.Sort(mailfull.AliasUserSlice(aliasUsers))
diff --git a/cmd/mailfull/command/catchall.go b/cmd/mailfull/cmd_catchall.go
similarity index 69%
rename from cmd/mailfull/command/catchall.go
rename to cmd/mailfull/cmd_catchall.go
index 3c1db48..43615a3 100644
--- a/cmd/mailfull/command/catchall.go
+++ b/cmd/mailfull/cmd_catchall.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// CatchAllCommand represents a CatchAllCommand.
-type CatchAllCommand struct {
-	Meta
+// CmdCatchAll represents a CmdCatchAll.
+type CmdCatchAll struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *CatchAllCommand) Synopsis() string {
+func (c *CmdCatchAll) Synopsis() string {
 	return "Show a catchall user."
 }
 
 // Help returns long-form help text.
-func (c *CatchAllCommand) Help() string {
+func (c *CmdCatchAll) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s domain
@@ -36,7 +37,7 @@ Required Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *CatchAllCommand) Run(args []string) int {
+func (c *CmdCatchAll) Run(args []string) int {
 	if len(args) != 1 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -46,13 +47,13 @@ func (c *CatchAllCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	catchAllUser, err := repo.CatchAllUser(domainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/catchallset.go b/cmd/mailfull/cmd_catchallset.go
similarity index 70%
rename from cmd/mailfull/command/catchallset.go
rename to cmd/mailfull/cmd_catchallset.go
index 24acd67..762a1b1 100644
--- a/cmd/mailfull/command/catchallset.go
+++ b/cmd/mailfull/cmd_catchallset.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// CatchAllSetCommand represents a CatchAllSetCommand.
-type CatchAllSetCommand struct {
-	Meta
+// CmdCatchAllSet represents a CmdCatchAllSet.
+type CmdCatchAllSet struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *CatchAllSetCommand) Synopsis() string {
+func (c *CmdCatchAllSet) Synopsis() string {
 	return "Set a catchall user."
 }
 
 // Help returns long-form help text.
-func (c *CatchAllSetCommand) Help() string {
+func (c *CmdCatchAllSet) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain user
@@ -42,7 +43,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *CatchAllSetCommand) Run(args []string) int {
+func (c *CmdCatchAllSet) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -59,18 +60,18 @@ func (c *CatchAllSetCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	catchAllUser, err := mailfull.NewCatchAllUser(userName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.CatchAllUserSet(domainName, catchAllUser); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -80,13 +81,13 @@ func (c *CatchAllSetCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/catchallunset.go b/cmd/mailfull/cmd_catchallunset.go
similarity index 68%
rename from cmd/mailfull/command/catchallunset.go
rename to cmd/mailfull/cmd_catchallunset.go
index a6f3fe9..8806a06 100644
--- a/cmd/mailfull/command/catchallunset.go
+++ b/cmd/mailfull/cmd_catchallunset.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// CatchAllUnsetCommand represents a CatchAllUnsetCommand.
-type CatchAllUnsetCommand struct {
-	Meta
+// CmdCatchAllUnset represents a CmdCatchAllUnset.
+type CmdCatchAllUnset struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *CatchAllUnsetCommand) Synopsis() string {
+func (c *CmdCatchAllUnset) Synopsis() string {
 	return "Unset a catchall user."
 }
 
 // Help returns long-form help text.
-func (c *CatchAllUnsetCommand) Help() string {
+func (c *CmdCatchAllUnset) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *CatchAllUnsetCommand) Run(args []string) int {
+func (c *CmdCatchAllUnset) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,12 +57,12 @@ func (c *CatchAllUnsetCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.CatchAllUserUnset(domainName); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -71,13 +72,13 @@ func (c *CatchAllUnsetCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/commit.go b/cmd/mailfull/cmd_commit.go
similarity index 61%
rename from cmd/mailfull/command/commit.go
rename to cmd/mailfull/cmd_commit.go
index 790b071..98276ef 100644
--- a/cmd/mailfull/command/commit.go
+++ b/cmd/mailfull/cmd_commit.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// CommitCommand represents a CommitCommand.
-type CommitCommand struct {
-	Meta
+// CmdCommit represents a CmdCommit.
+type CmdCommit struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *CommitCommand) Synopsis() string {
+func (c *CmdCommit) Synopsis() string {
 	return "Create databases from the structure of the MailData directory."
 }
 
 // Help returns long-form help text.
-func (c *CommitCommand) Help() string {
+func (c *CmdCommit) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s
@@ -32,22 +33,22 @@ Description:
 }
 
 // Run runs the command and returns the exit status.
-func (c *CommitCommand) Run(args []string) int {
+func (c *CmdCommit) Run(args []string) int {
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/domainadd.go b/cmd/mailfull/cmd_domainadd.go
similarity index 68%
rename from cmd/mailfull/command/domainadd.go
rename to cmd/mailfull/cmd_domainadd.go
index 1983d30..e7680d3 100644
--- a/cmd/mailfull/command/domainadd.go
+++ b/cmd/mailfull/cmd_domainadd.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// DomainAddCommand represents a DomainAddCommand.
-type DomainAddCommand struct {
-	Meta
+// CmdDomainAdd represents a CmdDomainAdd.
+type CmdDomainAdd struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *DomainAddCommand) Synopsis() string {
+func (c *CmdDomainAdd) Synopsis() string {
 	return "Create a new domain and postmaster."
 }
 
 // Help returns long-form help text.
-func (c *DomainAddCommand) Help() string {
+func (c *CmdDomainAdd) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *DomainAddCommand) Run(args []string) int {
+func (c *CmdDomainAdd) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,29 +57,29 @@ func (c *DomainAddCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	domain, err := mailfull.NewDomain(domainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.DomainCreate(domain); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	user, err := mailfull.NewUser("postmaster", mailfull.NeverMatchHashedPassword, nil)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.UserCreate(domainName, user); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -88,13 +89,13 @@ func (c *DomainAddCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/domaindel.go b/cmd/mailfull/cmd_domaindel.go
similarity index 70%
rename from cmd/mailfull/command/domaindel.go
rename to cmd/mailfull/cmd_domaindel.go
index a8b9be9..f521a26 100644
--- a/cmd/mailfull/command/domaindel.go
+++ b/cmd/mailfull/cmd_domaindel.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// DomainDelCommand represents a DomainDelCommand.
-type DomainDelCommand struct {
-	Meta
+// CmdDomainDel represents a CmdDomainDel.
+type CmdDomainDel struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *DomainDelCommand) Synopsis() string {
+func (c *CmdDomainDel) Synopsis() string {
 	return "Delete and backup a domain."
 }
 
 // Help returns long-form help text.
-func (c *DomainDelCommand) Help() string {
+func (c *CmdDomainDel) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *DomainDelCommand) Run(args []string) int {
+func (c *CmdDomainDel) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,12 +57,12 @@ func (c *DomainDelCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.DomainRemove(domainName); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -71,13 +72,13 @@ func (c *DomainDelCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/domaindisable.go b/cmd/mailfull/cmd_domaindisable.go
similarity index 66%
rename from cmd/mailfull/command/domaindisable.go
rename to cmd/mailfull/cmd_domaindisable.go
index c254c77..3a884b5 100644
--- a/cmd/mailfull/command/domaindisable.go
+++ b/cmd/mailfull/cmd_domaindisable.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// DomainDisableCommand represents a DomainDisableCommand.
-type DomainDisableCommand struct {
-	Meta
+// CmdDomainDisable represents a CmdDomainDisable.
+type CmdDomainDisable struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *DomainDisableCommand) Synopsis() string {
+func (c *CmdDomainDisable) Synopsis() string {
 	return "Disable a domain temporarily."
 }
 
 // Help returns long-form help text.
-func (c *DomainDisableCommand) Help() string {
+func (c *CmdDomainDisable) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *DomainDisableCommand) Run(args []string) int {
+func (c *CmdDomainDisable) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,24 +57,24 @@ func (c *DomainDisableCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	domain, err := repo.Domain(domainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	if domain == nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", mailfull.ErrDomainNotExist)
+		c.Meta.Errorf("%v\n", mailfull.ErrDomainNotExist)
 		return 1
 	}
 
 	domain.SetDisabled(true)
 
 	if err := repo.DomainUpdate(domain); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -83,13 +84,13 @@ func (c *DomainDisableCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/domainenable.go b/cmd/mailfull/cmd_domainenable.go
similarity index 66%
rename from cmd/mailfull/command/domainenable.go
rename to cmd/mailfull/cmd_domainenable.go
index 6fff76d..d185906 100644
--- a/cmd/mailfull/command/domainenable.go
+++ b/cmd/mailfull/cmd_domainenable.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// DomainEnableCommand represents a DomainEnableCommand.
-type DomainEnableCommand struct {
-	Meta
+// CmdDomainEnable represents a CmdDomainEnable.
+type CmdDomainEnable struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *DomainEnableCommand) Synopsis() string {
+func (c *CmdDomainEnable) Synopsis() string {
 	return "Enable a domain."
 }
 
 // Help returns long-form help text.
-func (c *DomainEnableCommand) Help() string {
+func (c *CmdDomainEnable) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] domain
@@ -40,7 +41,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *DomainEnableCommand) Run(args []string) int {
+func (c *CmdDomainEnable) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -56,24 +57,24 @@ func (c *DomainEnableCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	domain, err := repo.Domain(domainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	if domain == nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", mailfull.ErrDomainNotExist)
+		c.Meta.Errorf("%v\n", mailfull.ErrDomainNotExist)
 		return 1
 	}
 
 	domain.SetDisabled(false)
 
 	if err := repo.DomainUpdate(domain); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -83,13 +84,13 @@ func (c *DomainEnableCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/domains.go b/cmd/mailfull/cmd_domains.go
similarity index 69%
rename from cmd/mailfull/command/domains.go
rename to cmd/mailfull/cmd_domains.go
index 83b65d5..bc215f2 100644
--- a/cmd/mailfull/command/domains.go
+++ b/cmd/mailfull/cmd_domains.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"sort"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// DomainsCommand represents a DomainsCommand.
-type DomainsCommand struct {
-	Meta
+// CmdDomains represents a CmdDomains.
+type CmdDomains struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *DomainsCommand) Synopsis() string {
+func (c *CmdDomains) Synopsis() string {
 	return "Show domains."
 }
 
 // Help returns long-form help text.
-func (c *DomainsCommand) Help() string {
+func (c *CmdDomains) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s
@@ -34,16 +35,16 @@ Description:
 }
 
 // Run runs the command and returns the exit status.
-func (c *DomainsCommand) Run(args []string) int {
+func (c *CmdDomains) Run(args []string) int {
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	domains, err := repo.Domains()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	sort.Sort(mailfull.DomainSlice(domains))
diff --git a/cmd/mailfull/command/genconfig.go b/cmd/mailfull/cmd_genconfig.go
similarity index 71%
rename from cmd/mailfull/command/genconfig.go
rename to cmd/mailfull/cmd_genconfig.go
index e2a4b27..5cf4dd8 100644
--- a/cmd/mailfull/command/genconfig.go
+++ b/cmd/mailfull/cmd_genconfig.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// GenConfigCommand represents a GenConfigCommand.
-type GenConfigCommand struct {
-	Meta
+// CmdGenConfig represents a CmdGenConfig.
+type CmdGenConfig struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *GenConfigCommand) Synopsis() string {
+func (c *CmdGenConfig) Synopsis() string {
 	return "Write a Postfix or Dovecot configuration to stdout."
 }
 
 // Help returns long-form help text.
-func (c *GenConfigCommand) Help() string {
+func (c *CmdGenConfig) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s name
@@ -37,7 +38,7 @@ Required Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *GenConfigCommand) Run(args []string) int {
+func (c *CmdGenConfig) Run(args []string) int {
 	if len(args) != 1 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -47,7 +48,7 @@ func (c *GenConfigCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -59,7 +60,7 @@ func (c *GenConfigCommand) Run(args []string) int {
 		fmt.Fprintf(c.UI.Writer, "%s", repo.GenerateConfigDovecot())
 
 	default:
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] Specify \"postfix\" or \"dovecot\".\n")
+		c.Meta.Errorf("Specify \"postfix\" or \"dovecot\".\n")
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/init.go b/cmd/mailfull/cmd_init.go
similarity index 63%
rename from cmd/mailfull/command/init.go
rename to cmd/mailfull/cmd_init.go
index b915c7c..922e30d 100644
--- a/cmd/mailfull/command/init.go
+++ b/cmd/mailfull/cmd_init.go
@@ -1,23 +1,24 @@
-package command
+package main
 
 import (
 	"fmt"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// InitCommand represents a InitCommand.
-type InitCommand struct {
-	Meta
+// CmdInit represents a CmdInit.
+type CmdInit struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *InitCommand) Synopsis() string {
+func (c *CmdInit) Synopsis() string {
 	return "Initializes current directory as a Mailfull repository."
 }
 
 // Help returns long-form help text.
-func (c *InitCommand) Help() string {
+func (c *CmdInit) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s
@@ -32,9 +33,9 @@ Description:
 }
 
 // Run runs the command and returns the exit status.
-func (c *InitCommand) Run(args []string) int {
+func (c *CmdInit) Run(args []string) int {
 	if err := mailfull.InitRepository("."); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/useradd.go b/cmd/mailfull/cmd_useradd.go
similarity index 73%
rename from cmd/mailfull/command/useradd.go
rename to cmd/mailfull/cmd_useradd.go
index 943f493..b6695ab 100644
--- a/cmd/mailfull/command/useradd.go
+++ b/cmd/mailfull/cmd_useradd.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// UserAddCommand represents a UserAddCommand.
-type UserAddCommand struct {
-	Meta
+// CmdUserAdd represents a CmdUserAdd.
+type CmdUserAdd struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *UserAddCommand) Synopsis() string {
+func (c *CmdUserAdd) Synopsis() string {
 	return "Create a new user."
 }
 
 // Help returns long-form help text.
-func (c *UserAddCommand) Help() string {
+func (c *CmdUserAdd) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address
@@ -41,7 +42,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *UserAddCommand) Run(args []string) int {
+func (c *CmdUserAdd) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -65,18 +66,18 @@ func (c *UserAddCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	user, err := mailfull.NewUser(userName, mailfull.NeverMatchHashedPassword, nil)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if err := repo.UserCreate(domainName, user); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -86,13 +87,13 @@ func (c *UserAddCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/usercheckpw.go b/cmd/mailfull/cmd_usercheckpw.go
similarity index 77%
rename from cmd/mailfull/command/usercheckpw.go
rename to cmd/mailfull/cmd_usercheckpw.go
index 4ef780a..65542aa 100644
--- a/cmd/mailfull/command/usercheckpw.go
+++ b/cmd/mailfull/cmd_usercheckpw.go
@@ -1,25 +1,26 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 	"github.com/jsimonetti/pwscheme/ssha"
 )
 
-// UserCheckPwCommand represents a UserCheckPwCommand.
-type UserCheckPwCommand struct {
-	Meta
+// CmdUserCheckPw represents a CmdUserCheckPw.
+type CmdUserCheckPw struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *UserCheckPwCommand) Synopsis() string {
+func (c *CmdUserCheckPw) Synopsis() string {
 	return "Check user's password."
 }
 
 // Help returns long-form help text.
-func (c *UserCheckPwCommand) Help() string {
+func (c *CmdUserCheckPw) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s address [password]
@@ -43,7 +44,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *UserCheckPwCommand) Run(args []string) int {
+func (c *CmdUserCheckPw) Run(args []string) int {
 	if len(args) != 1 && len(args) != 2 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -66,24 +67,24 @@ func (c *UserCheckPwCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	user, err := repo.User(domainName, userName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	if user == nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", mailfull.ErrUserNotExist)
+		c.Meta.Errorf("%v\n", mailfull.ErrUserNotExist)
 		return 1
 	}
 
 	if len(args) != 2 {
 		input, err := c.UI.AskSecret(fmt.Sprintf("Enter password for %s:", address))
 		if err != nil {
-			fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+			c.Meta.Errorf("%v\n", err)
 			return 1
 		}
 
diff --git a/cmd/mailfull/command/userdel.go b/cmd/mailfull/cmd_userdel.go
similarity index 71%
rename from cmd/mailfull/command/userdel.go
rename to cmd/mailfull/cmd_userdel.go
index 858b8ff..cb35a9d 100644
--- a/cmd/mailfull/command/userdel.go
+++ b/cmd/mailfull/cmd_userdel.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// UserDelCommand represents a UserDelCommand.
-type UserDelCommand struct {
-	Meta
+// CmdUserDel represents a CmdUserDel.
+type CmdUserDel struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *UserDelCommand) Synopsis() string {
+func (c *CmdUserDel) Synopsis() string {
 	return "Delete and backup a user."
 }
 
 // Help returns long-form help text.
-func (c *UserDelCommand) Help() string {
+func (c *CmdUserDel) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address
@@ -41,7 +42,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *UserDelCommand) Run(args []string) int {
+func (c *CmdUserDel) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -65,17 +66,17 @@ func (c *UserDelCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	if userName == "postmaster" {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] Cannot delete postmaster.\n")
+		c.Meta.Errorf("Cannot delete postmaster.\n")
 		return 1
 	}
 
 	if err := repo.UserRemove(domainName, userName); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -85,13 +86,13 @@ func (c *UserDelCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/userpasswd.go b/cmd/mailfull/cmd_userpasswd.go
similarity index 73%
rename from cmd/mailfull/command/userpasswd.go
rename to cmd/mailfull/cmd_userpasswd.go
index bbd724c..1ea371e 100644
--- a/cmd/mailfull/command/userpasswd.go
+++ b/cmd/mailfull/cmd_userpasswd.go
@@ -1,25 +1,26 @@
-package command
+package main
 
 import (
 	"fmt"
 	"strings"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 	"github.com/jsimonetti/pwscheme/ssha"
 )
 
-// UserPasswdCommand represents a UserPasswdCommand.
-type UserPasswdCommand struct {
-	Meta
+// CmdUserPasswd represents a CmdUserPasswd.
+type CmdUserPasswd struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *UserPasswdCommand) Synopsis() string {
+func (c *CmdUserPasswd) Synopsis() string {
 	return "Update user's password."
 }
 
 // Help returns long-form help text.
-func (c *UserPasswdCommand) Help() string {
+func (c *CmdUserPasswd) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s [-n] address [password]
@@ -45,7 +46,7 @@ Optional Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *UserPasswdCommand) Run(args []string) int {
+func (c *CmdUserPasswd) Run(args []string) int {
 	noCommit, err := noCommitFlag(&args)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
@@ -74,33 +75,33 @@ func (c *UserPasswdCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	user, err := repo.User(domainName, userName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	if user == nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", mailfull.ErrUserNotExist)
+		c.Meta.Errorf("%v\n", mailfull.ErrUserNotExist)
 		return 1
 	}
 
 	if len(args) != 2 {
 		input1, err := c.UI.AskSecret(fmt.Sprintf("Enter new password for %s:", address))
 		if err != nil {
-			fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+			c.Meta.Errorf("%v\n", err)
 			return 1
 		}
 		input2, err := c.UI.AskSecret("Retype new password:")
 		if err != nil {
-			fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+			c.Meta.Errorf("%v\n", err)
 			return 1
 		}
 		if input1 != input2 {
-			fmt.Fprintf(c.UI.ErrorWriter, "[ERR] inputs do not match.\n")
+			c.Meta.Errorf("inputs do not match.\n")
 			return 1
 		}
 		rawPassword = input1
@@ -110,7 +111,7 @@ func (c *UserPasswdCommand) Run(args []string) int {
 	if rawPassword != "" {
 		str, err := ssha.Generate(rawPassword, 4)
 		if err != nil {
-			fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+			c.Meta.Errorf("%v\n", err)
 			return 1
 		}
 		hashedPassword = str
@@ -119,7 +120,7 @@ func (c *UserPasswdCommand) Run(args []string) int {
 	user.SetHashedPassword(hashedPassword)
 
 	if err := repo.UserUpdate(domainName, user); err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
@@ -129,13 +130,13 @@ func (c *UserPasswdCommand) Run(args []string) int {
 
 	mailData, err := repo.MailData()
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	err = repo.GenerateDatabases(mailData)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
diff --git a/cmd/mailfull/command/users.go b/cmd/mailfull/cmd_users.go
similarity index 71%
rename from cmd/mailfull/command/users.go
rename to cmd/mailfull/cmd_users.go
index 2f5038d..2dc0cda 100644
--- a/cmd/mailfull/command/users.go
+++ b/cmd/mailfull/cmd_users.go
@@ -1,24 +1,25 @@
-package command
+package main
 
 import (
 	"fmt"
 	"sort"
 
 	"github.com/directorz/mailfull-go"
+	"github.com/directorz/mailfull-go/cmd"
 )
 
-// UsersCommand represents a UsersCommand.
-type UsersCommand struct {
-	Meta
+// CmdUsers represents a CmdUsers.
+type CmdUsers struct {
+	cmd.Meta
 }
 
 // Synopsis returns a one-line synopsis.
-func (c *UsersCommand) Synopsis() string {
+func (c *CmdUsers) Synopsis() string {
 	return "Show users."
 }
 
 // Help returns long-form help text.
-func (c *UsersCommand) Help() string {
+func (c *CmdUsers) Help() string {
 	txt := fmt.Sprintf(`
 Usage:
     %s %s domain
@@ -37,7 +38,7 @@ Required Args:
 }
 
 // Run runs the command and returns the exit status.
-func (c *UsersCommand) Run(args []string) int {
+func (c *CmdUsers) Run(args []string) int {
 	if len(args) != 1 {
 		fmt.Fprintf(c.UI.ErrorWriter, "%v\n", c.Help())
 		return 1
@@ -47,13 +48,13 @@ func (c *UsersCommand) Run(args []string) int {
 
 	repo, err := mailfull.OpenRepository(".")
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 
 	users, err := repo.Users(targetDomainName)
 	if err != nil {
-		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
+		c.Meta.Errorf("%v\n", err)
 		return 1
 	}
 	sort.Sort(mailfull.UserSlice(users))
diff --git a/cmd/mailfull/command/main.go b/cmd/mailfull/command/main.go
deleted file mode 100644
index 66be466..0000000
--- a/cmd/mailfull/command/main.go
+++ /dev/null
@@ -1,30 +0,0 @@
-package command
-
-import (
-	"bytes"
-	"flag"
-
-	"github.com/mitchellh/cli"
-)
-
-// Meta is for `*Command` struct.
-type Meta struct {
-	UI         *cli.BasicUi
-	CmdName    string
-	SubCmdName string
-	Version    string
-}
-
-// noCommitFlag returns true if `pargs` has "-n" flag.
-// `pargs` is overwrites with non-flag arguments.
-func noCommitFlag(pargs *[]string) (bool, error) {
-	nFlag := false
-
-	flagSet := flag.NewFlagSet("", flag.ContinueOnError)
-	flagSet.SetOutput(&bytes.Buffer{})
-	flagSet.BoolVar(&nFlag, "n", nFlag, "")
-	err := flagSet.Parse(*pargs)
-	*pargs = flagSet.Args()
-
-	return nFlag, err
-}
diff --git a/cmd/mailfull/mailfull.go b/cmd/mailfull/main.go
similarity index 65%
rename from cmd/mailfull/mailfull.go
rename to cmd/mailfull/main.go
index 905a77a..ca74d78 100644
--- a/cmd/mailfull/mailfull.go
+++ b/cmd/mailfull/main.go
@@ -4,12 +4,14 @@ Command mailfull is a CLI application using the mailfull package.
 package main
 
 import (
+	"bytes"
+	"flag"
 	"fmt"
 	"os"
 	"path/filepath"
 
 	"github.com/directorz/mailfull-go"
-	"github.com/directorz/mailfull-go/cmd/mailfull/command"
+	"github.com/directorz/mailfull-go/cmd"
 	"github.com/mitchellh/cli"
 )
 
@@ -31,7 +33,7 @@ func main() {
 		Args:    os.Args[1:],
 	}
 
-	meta := command.Meta{
+	meta := cmd.Meta{
 		UI: &cli.BasicUi{
 			Reader:      os.Stdin,
 			Writer:      os.Stdout,
@@ -44,95 +46,95 @@ func main() {
 	c.Commands = map[string]cli.CommandFactory{
 		"init": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.InitCommand{Meta: meta}, nil
+			return &CmdInit{Meta: meta}, nil
 		},
 		"genconfig": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.GenConfigCommand{Meta: meta}, nil
+			return &CmdGenConfig{Meta: meta}, nil
 		},
 		"domains": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.DomainsCommand{Meta: meta}, nil
+			return &CmdDomains{Meta: meta}, nil
 		},
 		"domainadd": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.DomainAddCommand{Meta: meta}, nil
+			return &CmdDomainAdd{Meta: meta}, nil
 		},
 		"domaindel": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.DomainDelCommand{Meta: meta}, nil
+			return &CmdDomainDel{Meta: meta}, nil
 		},
 		"domaindisable": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.DomainDisableCommand{Meta: meta}, nil
+			return &CmdDomainDisable{Meta: meta}, nil
 		},
 		"domainenable": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.DomainEnableCommand{Meta: meta}, nil
+			return &CmdDomainEnable{Meta: meta}, nil
 		},
 		"aliasdomains": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasDomainsCommand{Meta: meta}, nil
+			return &CmdAliasDomains{Meta: meta}, nil
 		},
 		"aliasdomainadd": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasDomainAddCommand{Meta: meta}, nil
+			return &CmdAliasDomainAdd{Meta: meta}, nil
 		},
 		"aliasdomaindel": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasDomainDelCommand{Meta: meta}, nil
+			return &CmdAliasDomainDel{Meta: meta}, nil
 		},
 		"users": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.UsersCommand{Meta: meta}, nil
+			return &CmdUsers{Meta: meta}, nil
 		},
 		"useradd": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.UserAddCommand{Meta: meta}, nil
+			return &CmdUserAdd{Meta: meta}, nil
 		},
 		"userdel": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.UserDelCommand{Meta: meta}, nil
+			return &CmdUserDel{Meta: meta}, nil
 		},
 		"userpasswd": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.UserPasswdCommand{Meta: meta}, nil
+			return &CmdUserPasswd{Meta: meta}, nil
 		},
 		"usercheckpw": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.UserCheckPwCommand{Meta: meta}, nil
+			return &CmdUserCheckPw{Meta: meta}, nil
 		},
 		"aliasusers": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasUsersCommand{Meta: meta}, nil
+			return &CmdAliasUsers{Meta: meta}, nil
 		},
 		"aliasuseradd": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasUserAddCommand{Meta: meta}, nil
+			return &CmdAliasUserAdd{Meta: meta}, nil
 		},
 		"aliasusermod": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasUserModCommand{Meta: meta}, nil
+			return &CmdAliasUserMod{Meta: meta}, nil
 		},
 		"aliasuserdel": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.AliasUserDelCommand{Meta: meta}, nil
+			return &CmdAliasUserDel{Meta: meta}, nil
 		},
 		"catchall": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.CatchAllCommand{Meta: meta}, nil
+			return &CmdCatchAll{Meta: meta}, nil
 		},
 		"catchallset": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.CatchAllSetCommand{Meta: meta}, nil
+			return &CmdCatchAllSet{Meta: meta}, nil
 		},
 		"catchallunset": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.CatchAllUnsetCommand{Meta: meta}, nil
+			return &CmdCatchAllUnset{Meta: meta}, nil
 		},
 		"commit": func() (cli.Command, error) {
 			meta.SubCmdName = c.Subcommand()
-			return &command.CommitCommand{Meta: meta}, nil
+			return &CmdCommit{Meta: meta}, nil
 		},
 	}
 
@@ -143,3 +145,17 @@ func main() {
 
 	os.Exit(exitCode)
 }
+
+// noCommitFlag returns true if `pargs` has "-n" flag.
+// `pargs` is overwrites with non-flag arguments.
+func noCommitFlag(pargs *[]string) (bool, error) {
+	nFlag := false
+
+	flagSet := flag.NewFlagSet("", flag.ContinueOnError)
+	flagSet.SetOutput(&bytes.Buffer{})
+	flagSet.BoolVar(&nFlag, "n", nFlag, "")
+	err := flagSet.Parse(*pargs)
+	*pargs = flagSet.Args()
+
+	return nFlag, err
+}
diff --git a/cmd/meta.go b/cmd/meta.go
new file mode 100644
index 0000000..02e5334
--- /dev/null
+++ b/cmd/meta.go
@@ -0,0 +1,20 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/mitchellh/cli"
+)
+
+// Meta contains options to execute a command.
+type Meta struct {
+	UI         *cli.BasicUi
+	CmdName    string
+	SubCmdName string
+	Version    string
+}
+
+// Errorf prints the error to ErrorWriter with the prefix string.
+func (m Meta) Errorf(format string, v ...interface{}) {
+	fmt.Fprintf(m.UI.ErrorWriter, "[ERR] "+format, v...)
+}