InitSystem: resolve real path of exe path

Author: CarterLi

src/detection/initsystem/initsystem_linux.c

@@ -6,14 +6,21 @@ const char* ffDetectInitSystem(FFInitSystemResult* result)
     const char* error = ffProcessGetBasicInfoLinux((int) result->pid, &result->name, NULL, NULL);
     if (error) return error;
 
-    const char* exeName;
-
-    ffProcessGetInfoLinux((int) result->pid, &result->name, &result->exe, &exeName, NULL);
+    const char* _;
+    // In linux /proc/1/exe is not readable
+    ffProcessGetInfoLinux((int) result->pid, &result->name, &result->exe, &_, NULL);
+    if (result->exe.chars[0] == '/')
+    {
+        // In some old system, /sbin/init is a symlink
+        char buf[PATH_MAX];
+        if (realpath(result->exe.chars, buf))
+            ffStrbufSetS(&result->exe, buf);
+    }
 
     if (ffStrbufEqualS(&result->name, "systemd"))
     {
         if (ffProcessAppendStdOut(&result->version, (char* const[]) {
-            "systemctl",
+            result->exe.chars, // use exe path in case users have another systemd installed
             "--version",
             NULL,
         }) == NULL && result->version.length)
@@ -25,22 +32,12 @@ const char* ffDetectInitSystem(FFInitSystemResult* result)
                 ffStrbufSubstrBefore(&result->version, iEnd);
                 ffStrbufSubstrAfter(&result->version, iStart);
             }
-            else
-            {
-                iStart = ffStrbufFirstIndexC(&result->version, ' ');
-                if (iStart < result->version.length)
-                {
-                    uint32_t iEnd = ffStrbufNextIndexC(&result->version, iStart + 1, ' ');
-                    ffStrbufSubstrBefore(&result->version, iEnd);
-                    ffStrbufSubstrAfter(&result->version, iStart);
-                }
-            }
         }
     }
     else if (ffStrbufEqualS(&result->name, "launchd"))
     {
         if (ffProcessAppendStdOut(&result->version, (char* const[]) {
-            "launchctl",
+            "/bin/launchctl",
             "version",
             NULL,
         }) == NULL && result->version.length)