Update Zig Cat example

* added reading from stdin if no paths are provided
* using streams to encapsulate common behaviour in print_from_stream

zig-cat/src/main.zig

@@ -1,9 +1,17 @@
 const std = @import("std");
 
 pub fn main() !void {
+    if (std.os.argv.len > 1) {
+        handle_file_input();
+    } else {
+        handle_stdin_input();
+    }
+}
+
+pub fn handle_file_input() void {
     for (std.os.argv[1..]) |file_path_sent| {
         const file_path = std.mem.span(file_path_sent);
-        const file = std.fs.openFileAbsolute(
+        const file = std.fs.cwd().openFile(
             file_path,
             .{ .mode = .read_only },
         ) catch |err| {
@@ -12,17 +20,25 @@ pub fn main() !void {
         };
         defer file.close();
 
-        while (true) {
-            var ar = std.ArrayList(u8).init(std.heap.page_allocator);
-            defer ar.deinit();
+        print_from_stream(file.reader().any()) catch continue;
+    }
+}
 
-            file.reader().streamUntilDelimiter(
-                ar.writer(),
+pub fn handle_stdin_input() void {
+    print_from_stream(std.io.getStdIn().reader().any()) catch return;
+}
+
+pub fn print_from_stream(stream: std.io.AnyReader) !void {
+    while (true) {
+        var line = std.ArrayList(u8).init(std.heap.page_allocator);
+        defer line.deinit();
+
+        try stream.streamUntilDelimiter(
+            line.writer(),
             '\n',
             null,
-            ) catch break;
+        );
 
-            std.debug.print("{s}\n", .{ar.items});
-        }
+        std.debug.print("{s}\n", .{line.items});
     }
 }