diff --git a/weed/command/shell.go b/weed/command/shell.go
index 962fe26ee..4053646ad 100644
--- a/weed/command/shell.go
+++ b/weed/command/shell.go
@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/seaweedfs/seaweedfs/weed/pb"
 
@@ -60,7 +61,7 @@ func runShell(command *Command, args []string) bool {
 		filerAddress = viper.GetString("cluster." + cluster + ".filer")
 	}
 	shellOptions.FilerAddress = pb.ServerAddress(filerAddress)
-	fmt.Printf("master: %s filer: %s\n", *shellOptions.Masters, shellOptions.FilerAddress)
+	fmt.Fprintf(os.Stderr, "master: %s filer: %s\n", *shellOptions.Masters, shellOptions.FilerAddress)
 
 	shell.RunShell(shellOptions)
 
diff --git a/weed/shell/command_s3_policy_attach.go b/weed/shell/command_s3_policy_attach.go
index b170d6e56..a9883edfa 100644
--- a/weed/shell/command_s3_policy_attach.go
+++ b/weed/shell/command_s3_policy_attach.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -74,8 +75,7 @@ func (c *commandS3PolicyAttach) Do(args []string, commandEnv *CommandEnv, writer
 		// Check if already attached
 		for _, p := range resp.Identity.PolicyNames {
 			if p == *policy {
-				fmt.Fprintf(writer, "Policy %q is already attached to user %q.\n", *policy, *user)
-				return nil
+				return json.NewEncoder(writer).Encode(map[string]string{"policy": *policy, "user": *user})
 			}
 		}
 
@@ -88,7 +88,6 @@ func (c *commandS3PolicyAttach) Do(args []string, commandEnv *CommandEnv, writer
 			return err
 		}
 
-		fmt.Fprintf(writer, "Attached policy %q to user %q\n", *policy, *user)
-		return nil
+		return json.NewEncoder(writer).Encode(map[string]string{"policy": *policy, "user": *user})
 	}, commandEnv.option.FilerAddress.ToGrpcAddress(), false, commandEnv.option.GrpcDialOption)
 }
diff --git a/weed/shell/command_s3_policy_detach.go b/weed/shell/command_s3_policy_detach.go
index d66896f29..26971ab9b 100644
--- a/weed/shell/command_s3_policy_detach.go
+++ b/weed/shell/command_s3_policy_detach.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -84,7 +85,6 @@ func (c *commandS3PolicyDetach) Do(args []string, commandEnv *CommandEnv, writer
 			return err
 		}
 
-		fmt.Fprintf(writer, "Detached policy %q from user %q\n", *policy, *user)
-		return nil
+		return json.NewEncoder(writer).Encode(map[string]string{"policy": *policy, "user": *user})
 	}, commandEnv.option.FilerAddress.ToGrpcAddress(), false, commandEnv.option.GrpcDialOption)
 }
diff --git a/weed/shell/command_s3_user_create.go b/weed/shell/command_s3_user_create.go
index c9a602213..8fd056ab6 100644
--- a/weed/shell/command_s3_user_create.go
+++ b/weed/shell/command_s3_user_create.go
@@ -2,9 +2,11 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
+	"os"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/iam"
@@ -34,6 +36,8 @@ func (c *commandS3UserCreate) Help() string {
 	are omitted, they are generated automatically.
 
 	After creating a user, attach policies with s3.policy.attach.
+
+	Output: JSON to stdout. Secret key is printed to stderr only.
 `
 }
 
@@ -56,8 +60,10 @@ func (c *commandS3UserCreate) Do(args []string, commandEnv *CommandEnv, writer i
 
 	ak := *accessKey
 	sk := *secretKey
+	generated := false
 
 	if ak == "" && sk == "" {
+		generated = true
 		var err error
 		ak, err = iam.GenerateRandomString(iam.AccessKeyIdLength, iam.CharsetUpper)
 		if err != nil {
@@ -93,10 +99,13 @@ func (c *commandS3UserCreate) Do(args []string, commandEnv *CommandEnv, writer i
 		return err
 	}
 
-	fmt.Fprintf(writer, "Created user %q\n", *name)
-	fmt.Fprintf(writer, "Access Key: %s\n", ak)
-	fmt.Fprintf(writer, "Secret Key: %s\n", sk)
-	fmt.Fprintln(writer)
-	fmt.Fprintln(writer, "Save these credentials - the secret key cannot be retrieved later.")
-	return nil
+	if generated {
+		fmt.Fprintf(os.Stderr, "Secret Key: %s\n", sk)
+		fmt.Fprintf(os.Stderr, "Save this secret key - it cannot be retrieved later.\n")
+	}
+
+	return json.NewEncoder(writer).Encode(map[string]string{
+		"name":       *name,
+		"access_key": ak,
+	})
 }
diff --git a/weed/shell/command_s3_user_delete.go b/weed/shell/command_s3_user_delete.go
index b74435888..6d4698b1c 100644
--- a/weed/shell/command_s3_user_delete.go
+++ b/weed/shell/command_s3_user_delete.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -56,6 +57,5 @@ func (c *commandS3UserDelete) Do(args []string, commandEnv *CommandEnv, writer i
 		return err
 	}
 
-	fmt.Fprintf(writer, "Deleted user %q\n", *name)
-	return nil
+	return json.NewEncoder(writer).Encode(map[string]string{"name": *name})
 }
diff --git a/weed/shell/command_s3_user_disable.go b/weed/shell/command_s3_user_disable.go
index 3799460be..34af926fe 100644
--- a/weed/shell/command_s3_user_disable.go
+++ b/weed/shell/command_s3_user_disable.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -62,7 +63,6 @@ func (c *commandS3UserDisable) Do(args []string, commandEnv *CommandEnv, writer
 		}
 
 		if resp.Identity.Disabled {
-			fmt.Fprintf(writer, "User %q is already disabled.\n", *name)
 			return nil
 		}
 
@@ -77,6 +77,5 @@ func (c *commandS3UserDisable) Do(args []string, commandEnv *CommandEnv, writer
 		return err
 	}
 
-	fmt.Fprintf(writer, "Disabled user %q\n", *name)
-	return nil
+	return json.NewEncoder(writer).Encode(map[string]string{"name": *name, "status": "disabled"})
 }
diff --git a/weed/shell/command_s3_user_enable.go b/weed/shell/command_s3_user_enable.go
index 76a3635ed..3040db2c3 100644
--- a/weed/shell/command_s3_user_enable.go
+++ b/weed/shell/command_s3_user_enable.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
@@ -58,22 +59,19 @@ func (c *commandS3UserEnable) Do(args []string, commandEnv *CommandEnv, writer i
 			return fmt.Errorf("user %q returned empty identity", *name)
 		}
 
-		if !resp.Identity.Disabled {
-			fmt.Fprintf(writer, "User %q is already enabled.\n", *name)
-			return nil
+		if resp.Identity.Disabled {
+			resp.Identity.Disabled = false
+			_, err = client.UpdateUser(ctx, &iam_pb.UpdateUserRequest{
+				Username: *name,
+				Identity: resp.Identity,
+			})
+			return err
 		}
-
-		resp.Identity.Disabled = false
-		_, err = client.UpdateUser(ctx, &iam_pb.UpdateUserRequest{
-			Username: *name,
-			Identity: resp.Identity,
-		})
-		return err
+		return nil
 	}, commandEnv.option.FilerAddress.ToGrpcAddress(), false, commandEnv.option.GrpcDialOption)
 	if err != nil {
 		return err
 	}
 
-	fmt.Fprintf(writer, "Enabled user %q\n", *name)
-	return nil
+	return json.NewEncoder(writer).Encode(map[string]string{"name": *name, "status": "enabled"})
 }
diff --git a/weed/shell/command_s3_user_list.go b/weed/shell/command_s3_user_list.go
index 7955b3e1a..f0107d536 100644
--- a/weed/shell/command_s3_user_list.go
+++ b/weed/shell/command_s3_user_list.go
@@ -2,10 +2,9 @@ package shell
 
 import (
 	"context"
-	"fmt"
+	"encoding/json"
 	"io"
 	"strings"
-	"text/tabwriter"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/pb"
@@ -29,7 +28,7 @@ func (c *commandS3UserList) Help() string {
 
 	s3.user.list
 
-	Lists all users with their status, attached policies, and credential count.
+	Output: JSON array of users with status, policies, and credential count.
 `
 }
 
@@ -37,6 +36,13 @@ func (c *commandS3UserList) HasTag(CommandTag) bool {
 	return false
 }
 
+type s3UserListEntry struct {
+	Name     string   `json:"name"`
+	Status   string   `json:"status"`
+	Policies []string `json:"policies"`
+	Keys     int      `json:"keys"`
+}
+
 func (c *commandS3UserList) Do(args []string, commandEnv *CommandEnv, writer io.Writer) error {
 	return pb.WithGrpcClient(false, 0, func(conn *grpc.ClientConn) error {
 		client := iam_pb.NewSeaweedIdentityAccessManagementClient(conn)
@@ -48,27 +54,27 @@ func (c *commandS3UserList) Do(args []string, commandEnv *CommandEnv, writer io.
 			return err
 		}
 
-		identities := resp.Configuration.GetIdentities()
-		if len(identities) == 0 {
-			fmt.Fprintln(writer, "No users found.")
-			return nil
-		}
-
-		tw := tabwriter.NewWriter(writer, 0, 4, 2, ' ', 0)
-		fmt.Fprintln(tw, "NAME\tSTATUS\tPOLICIES\tKEYS")
-
-		for _, id := range identities {
+		var result []s3UserListEntry
+		for _, id := range resp.Configuration.GetIdentities() {
 			status := "enabled"
 			if id.Disabled {
 				status = "disabled"
 			}
-			policies := "-"
-			if len(id.PolicyNames) > 0 {
-				policies = joinMax(id.PolicyNames, 3)
+			policies := id.PolicyNames
+			if policies == nil {
+				policies = []string{}
 			}
-			fmt.Fprintf(tw, "%s\t%s\t%s\t%d\n", id.Name, status, policies, len(id.Credentials))
+			result = append(result, s3UserListEntry{
+				Name:     id.Name,
+				Status:   status,
+				Policies: policies,
+				Keys:     len(id.Credentials),
+			})
 		}
-		return tw.Flush()
+		if result == nil {
+			result = []s3UserListEntry{}
+		}
+		return json.NewEncoder(writer).Encode(result)
 	}, commandEnv.option.FilerAddress.ToGrpcAddress(), false, commandEnv.option.GrpcDialOption)
 }
 
diff --git a/weed/shell/command_s3_user_show.go b/weed/shell/command_s3_user_show.go
index 1841ab1b9..92ba126cd 100644
--- a/weed/shell/command_s3_user_show.go
+++ b/weed/shell/command_s3_user_show.go
@@ -2,10 +2,10 @@ package shell
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"io"
-	"strings"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/pb"
@@ -28,6 +28,8 @@ func (c *commandS3UserShow) Help() string {
 	return `show details of an S3 IAM user
 
 	s3.user.show -name <username>
+
+	Output: JSON object with user details.
 `
 }
 
@@ -35,6 +37,28 @@ func (c *commandS3UserShow) HasTag(CommandTag) bool {
 	return false
 }
 
+type s3CredentialInfo struct {
+	AccessKey string `json:"access_key"`
+	Status    string `json:"status"`
+}
+
+type s3AccountInfo struct {
+	ID          string `json:"id,omitempty"`
+	DisplayName string `json:"display_name,omitempty"`
+	Email       string `json:"email,omitempty"`
+}
+
+type s3UserShowResult struct {
+	Name            string            `json:"name"`
+	Status          string            `json:"status"`
+	Source          string            `json:"source"`
+	Account         *s3AccountInfo    `json:"account,omitempty"`
+	Policies        []string          `json:"policies"`
+	Actions         []string          `json:"actions,omitempty"`
+	Credentials     []s3CredentialInfo `json:"credentials"`
+	ServiceAccounts []string          `json:"service_accounts,omitempty"`
+}
+
 func (c *commandS3UserShow) Do(args []string, commandEnv *CommandEnv, writer io.Writer) error {
 	f := flag.NewFlagSet(c.Name(), flag.ContinueOnError)
 	name := f.String("name", "", "user name")
@@ -69,51 +93,45 @@ func (c *commandS3UserShow) Do(args []string, commandEnv *CommandEnv, writer io.
 			source = "static"
 		}
 
-		fmt.Fprintf(writer, "Name:     %s\n", id.Name)
-		fmt.Fprintf(writer, "Status:   %s\n", status)
-		fmt.Fprintf(writer, "Source:   %s\n", source)
+		result := s3UserShowResult{
+			Name:   id.Name,
+			Status: status,
+			Source: source,
+		}
 
-		if id.Account != nil {
-			if id.Account.Id != "" {
-				fmt.Fprintf(writer, "Account:  %s", id.Account.Id)
-				if id.Account.DisplayName != "" {
-					fmt.Fprintf(writer, " (%s)", id.Account.DisplayName)
-				}
-				fmt.Fprintln(writer)
-			}
-			if id.Account.EmailAddress != "" {
-				fmt.Fprintf(writer, "Email:    %s\n", id.Account.EmailAddress)
+		if id.Account != nil && (id.Account.Id != "" || id.Account.DisplayName != "" || id.Account.EmailAddress != "") {
+			result.Account = &s3AccountInfo{
+				ID:          id.Account.Id,
+				DisplayName: id.Account.DisplayName,
+				Email:       id.Account.EmailAddress,
 			}
 		}
 
-		if len(id.PolicyNames) > 0 {
-			fmt.Fprintf(writer, "Policies: %s\n", strings.Join(id.PolicyNames, ", "))
-		} else {
-			fmt.Fprintln(writer, "Policies: (none)")
+		result.Policies = id.PolicyNames
+		if result.Policies == nil {
+			result.Policies = []string{}
 		}
 
 		if len(id.Actions) > 0 {
-			fmt.Fprintf(writer, "Actions:  %s\n", strings.Join(id.Actions, ", "))
+			result.Actions = id.Actions
 		}
 
-		fmt.Fprintln(writer)
-		if len(id.Credentials) > 0 {
-			fmt.Fprintln(writer, "Credentials:")
-			for _, cred := range id.Credentials {
-				st := cred.Status
-				if st == "" {
-					st = "Active"
-				}
-				fmt.Fprintf(writer, "  %s  %s\n", cred.AccessKey, st)
+		result.Credentials = make([]s3CredentialInfo, 0, len(id.Credentials))
+		for _, cred := range id.Credentials {
+			st := cred.Status
+			if st == "" {
+				st = "Active"
 			}
-		} else {
-			fmt.Fprintln(writer, "Credentials: (none)")
+			result.Credentials = append(result.Credentials, s3CredentialInfo{
+				AccessKey: cred.AccessKey,
+				Status:    st,
+			})
 		}
 
 		if len(id.ServiceAccountIds) > 0 {
-			fmt.Fprintf(writer, "\nService Accounts: %s\n", strings.Join(id.ServiceAccountIds, ", "))
+			result.ServiceAccounts = id.ServiceAccountIds
 		}
 
-		return nil
+		return json.NewEncoder(writer).Encode(result)
 	}, commandEnv.option.FilerAddress.ToGrpcAddress(), false, commandEnv.option.GrpcDialOption)
 }
diff --git a/weed/shell/shell_liner.go b/weed/shell/shell_liner.go
index 2d756dc63..cc17e80f2 100644
--- a/weed/shell/shell_liner.go
+++ b/weed/shell/shell_liner.go
@@ -1,6 +1,7 @@
 package shell
 
 import (
+	"bufio"
 	"context"
 	"fmt"
 	"io"
@@ -64,31 +65,46 @@ func RunShell(options ShellOptions) {
 			}
 			return nil
 		})
-		fmt.Printf("master: %s ", *options.Masters)
+		fmt.Fprintf(os.Stderr, "master: %s ", *options.Masters)
 		if len(filers) > 0 {
-			fmt.Printf("filers: %v", filers)
+			fmt.Fprintf(os.Stderr, "filers: %v", filers)
 			commandEnv.option.FilerAddress = filers[rand.IntN(len(filers))]
 		}
-		fmt.Println()
+		fmt.Fprintln(os.Stderr)
 	}
 
-	for {
-		cmd, err := line.Prompt("> ")
-		if err != nil {
-			if err != io.EOF {
-				fmt.Printf("%v\n", err)
-			}
-			return
-		}
-
-		if strings.TrimSpace(cmd) != "" {
-			line.AppendHistory(cmd)
-		}
-
-		for _, c := range util.StringSplit(cmd, ";") {
-			if processEachCmd(c, commandEnv) {
+	if liner.TerminalSupported() {
+		for {
+			cmd, err := line.Prompt("> ")
+			if err != nil {
+				if err != io.EOF {
+					fmt.Fprintf(os.Stderr, "%v\n", err)
+				}
 				return
 			}
+
+			if strings.TrimSpace(cmd) != "" {
+				line.AppendHistory(cmd)
+			}
+
+			for _, c := range util.StringSplit(cmd, ";") {
+				if processEachCmd(c, commandEnv) {
+					return
+				}
+			}
+		}
+	} else {
+		scanner := bufio.NewScanner(os.Stdin)
+		for scanner.Scan() {
+			cmd := scanner.Text()
+			for _, c := range util.StringSplit(cmd, ";") {
+				if processEachCmd(c, commandEnv) {
+					return
+				}
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			fmt.Fprintf(os.Stderr, "error reading stdin: %v\n", err)
 		}
 	}
 }
@@ -232,10 +248,10 @@ func loadHistory() {
 
 func saveHistory() {
 	if f, err := os.Create(historyPath); err != nil {
-		fmt.Printf("Error creating history file: %v\n", err)
+		fmt.Fprintf(os.Stderr, "Error creating history file: %v\n", err)
 	} else {
 		if _, err = line.WriteHistory(f); err != nil {
-			fmt.Printf("Error writing history file: %v\n", err)
+			fmt.Fprintf(os.Stderr, "Error writing history file: %v\n", err)
 		}
 		f.Close()
 	}