Add standalone greet tool

tools/greet.zig

@@ -0,0 +1,70 @@
+const std = @import("std");
+
+pub fn main() !void {
+    const allocator = std.heap.page_allocator;
+
+    const args = try std.process.argsAlloc(allocator);
+    defer std.process.argsFree(allocator, args);
+
+    const stdout = std.fs.File.stdout();
+    const stderr = std.fs.File.stderr();
+    _ = stderr;
+
+    // args[0] is the program name, args[1..] are the actual arguments
+    const user_args = if (args.len > 1) args[1..] else &[_][]const u8{};
+
+    if (user_args.len > 0) {
+        const first = user_args[0];
+
+        if (std.mem.eql(u8, first, "--version")) {
+            try stdout.writeAll("greet 1.0.0\n");
+            return;
+        }
+
+        if (std.mem.eql(u8, first, "--help")) {
+            try stdout.writeAll("Usage: greet [OPTIONS] [NAME...]\n\nOptions:\n  --version   Print version information and exit\n  --help      Print this help message and exit\n\nArguments:\n  NAME...     One or more names to greet\n\nIf no arguments are given, greets the world.\n");
+            return;
+        }
+
+        // Join all args with spaces
+        // First calculate total length needed
+        var total_len: usize = 0;
+        for (user_args, 0..) |arg, i| {
+            total_len += arg.len;
+            if (i < user_args.len - 1) {
+                total_len += 1; // space
+            }
+        }
+
+        // "Hello, " + joined + "!\n"
+        const prefix = "Hello, ";
+        const suffix = "!\n";
+        const buf_size = prefix.len + total_len + suffix.len;
+
+        var buf: [4096]u8 = undefined;
+        if (buf_size > buf.len) {
+            try stdout.writeAll("Hello, World!\n");
+            return;
+        }
+
+        var pos: usize = 0;
+        @memcpy(buf[pos .. pos + prefix.len], prefix);
+        pos += prefix.len;
+
+        for (user_args, 0..) |arg, i| {
+            @memcpy(buf[pos .. pos + arg.len], arg);
+            pos += arg.len;
+            if (i < user_args.len - 1) {
+                buf[pos] = ' ';
+                pos += 1;
+            }
+        }
+
+        @memcpy(buf[pos .. pos + suffix.len], suffix);
+        pos += suffix.len;
+
+        try stdout.writeAll(buf[0..pos]);
+    } else {
+        try stdout.writeAll("Hello, World!\n");
+    }
+}