Log config output path in generate command (#4)

Author: rainbend

README.md

@@ -79,6 +79,30 @@ Install a specific version:
 curl -fsSL https://raw.githubusercontent.com/rainbend/sing-box-subscribe-cli/main/install.sh | VERSION=v1.0.0 bash
 ```
 
+Use `ExecStartPre` in a systemd unit when you want to regenerate the sing-box config before starting sing-box:
+
+```ini
+[Unit]
+Description=sing-box service
+Documentation=https://sing-box.sagernet.org
+After=network.target nss-lookup.target network-online.target
+
+[Service]
+CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_SYS_PTRACE CAP_DAC_READ_SEARCH
+AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_SYS_PTRACE CAP_DAC_READ_SEARCH
+ExecStartPre=/usr/local/bin/sing-box-sub --out /etc/sing-box/config.json 'https://example.com/api/v1/client/subscribe?token=REDACTED'
+ExecStart=/usr/bin/sing-box -D /var/lib/sing-box -C /etc/sing-box run
+ExecReload=/bin/kill -HUP $MAINPID
+Restart=on-failure
+RestartSec=10s
+LimitNOFILE=infinity
+
+[Install]
+WantedBy=multi-user.target
+```
+
+If `ExecStartPre` fails, systemd stops the startup before launching sing-box. Make sure `/usr/local/bin/sing-box-sub` exists, the service can write `/etc/sing-box/config.json`, and the subscription URL is reachable when the service starts.
+
 ### Windows
 
 Download the matching `.exe` from the [GitHub Releases page](https://github.com/rainbend/sing-box-subscribe-cli/releases), rename it to `sing-box-sub.exe` if you like, and place it in a directory listed in `PATH`.

README.zh-CN.md

@@ -79,6 +79,30 @@ curl -fsSL https://raw.githubusercontent.com/rainbend/sing-box-subscribe-cli/mai
 curl -fsSL https://raw.githubusercontent.com/rainbend/sing-box-subscribe-cli/main/install.sh | VERSION=v1.0.0 bash
 ```
 
+如果希望在 sing-box 启动前自动重新生成配置，可以在 systemd unit 中使用 `ExecStartPre`：
+
+```ini
+[Unit]
+Description=sing-box service
+Documentation=https://sing-box.sagernet.org
+After=network.target nss-lookup.target network-online.target
+
+[Service]
+CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_SYS_PTRACE CAP_DAC_READ_SEARCH
+AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_SYS_PTRACE CAP_DAC_READ_SEARCH
+ExecStartPre=/usr/local/bin/sing-box-sub --out /etc/sing-box/config.json 'https://example.com/api/v1/client/subscribe?token=REDACTED'
+ExecStart=/usr/bin/sing-box -D /var/lib/sing-box -C /etc/sing-box run
+ExecReload=/bin/kill -HUP $MAINPID
+Restart=on-failure
+RestartSec=10s
+LimitNOFILE=infinity
+
+[Install]
+WantedBy=multi-user.target
+```
+
+如果 `ExecStartPre` 执行失败，systemd 会在启动 sing-box 前停止本次启动流程。请确认 `/usr/local/bin/sing-box-sub` 已存在，服务有权限写入 `/etc/sing-box/config.json`，并且服务启动时可以访问订阅 URL。
+
 ### Windows
 
 从 [GitHub Releases 页面](https://github.com/rainbend/sing-box-subscribe-cli/releases) 下载匹配的 `.exe` 文件，可以重命名为 `sing-box-sub.exe`，并放到 `PATH` 包含的目录。

cmd/sing-box-subscribe-cli/main.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/rainbend/sing-box-subscribe-cli/internal/subconv"
@@ -112,12 +113,25 @@ func runGenerate(cmd *cobra.Command, opts subconv.Options, timeout time.Duration
 		fmt.Fprintf(stderr, " with %d warnings", len(result.Warnings))
 	}
 	fmt.Fprintln(stderr)
+	if opts.Output == "-" {
+		fmt.Fprintln(stderr, "config output: stdout")
+	} else {
+		fmt.Fprintf(stderr, "config path: %s\n", displayPath(opts.Output))
+	}
 	for _, warning := range result.Warnings {
 		fmt.Fprintf(stderr, "warning: %s\n", warning)
 	}
 	return nil
 }
 
+func displayPath(path string) string {
+	absolute, err := filepath.Abs(path)
+	if err != nil {
+		return path
+	}
+	return absolute
+}
+
 func writeJSON(path string, value any) error {
 	var out *os.File
 	if path == "-" {

cmd/sing-box-subscribe-cli/main_test.go

@@ -76,6 +76,9 @@ proxies:
 	if !strings.Contains(stderr, "generated 1 nodes") {
 		t.Fatalf("stderr missing generated count:\n%s", stderr)
 	}
+	if !strings.Contains(stderr, "config path: "+outputPath) {
+		t.Fatalf("stderr missing output path:\n%s", stderr)
+	}
 	output, err := os.ReadFile(outputPath)
 	if err != nil {
 		t.Fatal(err)