The std.fs.File.Reader.read function was removed in Zig v0.15.2.

src/linux/system.zig

@@ -122,8 +122,7 @@ pub fn getWindowManagerInfo(allocator: std.mem.Allocator) ![]const u8 {
 
             // NOTE: https://stackoverflow.com/questions/23534263/what-is-the-maximum-allowed-limit-on-the-length-of-a-process-name
             var file_buf: [16]u8 = undefined;
-            var reader = std.fs.File.Reader.init(file, &file_buf);
-            const read = try reader.read(&file_buf);
+            const read = try file.read(&file_buf);
             const proc_name = file_buf[0..read];
 
             const proc_name_trimmed = std.mem.trim(u8, proc_name, "\n");