discover daemon state dir from cmdline when environ is unreadable

When the daemon runs as a different user (e.g. via systemd), the client
cannot read /proc/<pid>/environ due to permissions. Fall back to
parsing the cmdline for -D / --state-dir flags, which are world-readable.

Fixes 'error: no logs for <service>' when client and daemon run as
different users.

v0.1.1

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rss"
-version = "0.1.0"
+version = "0.1.1"
 edition = "2021"
 
 [dependencies]

src/state.rs

@@ -30,16 +30,41 @@ fn discover_daemon_state_dir() -> Option<PathBuf> {
         if !args.contains(&"daemon") {
             continue;
         }
-        let environ = std::fs::read(format!("/proc/{}/environ", pid)).ok()?;
+        // Try RSS_STATE_DIR from environ first
-        for var in environ.split(|&b| b == 0) {
+        if let Ok(environ) = std::fs::read(format!("/proc/{}/environ", pid)) {
-            if let Ok(var_str) = std::str::from_utf8(var) {
+            for var in environ.split(|&b| b == 0) {
-                if let Some(val) = var_str.strip_prefix("RSS_STATE_DIR=") {
+                if let Ok(var_str) = std::str::from_utf8(var) {
-                    if !val.is_empty() {
+                    if let Some(val) = var_str.strip_prefix("RSS_STATE_DIR=") {
-                        return Some(PathBuf::from(val));
+                        if !val.is_empty() {
+                            return Some(PathBuf::from(val));
+                        }
                     }
                 }
             }
         }
+        // Fallback: parse cmdline for -D / --state-dir (works across users)
+        let mut i = 0;
+        while i < args.len() {
+            let next = if args[i] == "-D" || args[i] == "--state-dir" {
+                args.get(i + 1).map(|s| s.to_string())
+            } else if let Some(val) = args[i].strip_prefix("--state-dir=") {
+                Some(val.to_string())
+            } else if let Some(val) = args[i].strip_prefix("-D") {
+                if val.is_empty() {
+                    args.get(i + 1).map(|s| s.to_string())
+                } else {
+                    Some(val.to_string())
+                }
+            } else {
+                None
+            };
+            if let Some(dir) = next {
+                if !dir.is_empty() {
+                    return Some(PathBuf::from(dir));
+                }
+            }
+            i += 1;
+        }
     }
     None
 }