Add cowsay command

build.zig

@@ -118,6 +118,7 @@ fn buildBinaries(
         "repeat",
         "tcp-proxy",
         "timeout",
+        "cowsay",
     }) |name| {
         try buildBinary(
             b,

docs/content/programs/cowsay.org

@@ -0,0 +1,57 @@
+#+TITLE: cowsay
+#+DATE: 2026-03-16T04:25:00+0800
+#+LASTMOD: 2026-03-16T04:25:00+0800
+#+TYPE: docs
+#+DESCRIPTION: Generate an ASCII picture of a cow saying something
+
+#+begin_src bash :results verbatim :exports results :wrap example :dir ../../..
+./zig-out/bin/cowsay -h
+#+end_src
+
+#+RESULTS:
+#+begin_example
+ USAGE:
+     ./zig-out/bin/cowsay [OPTIONS] [--] [message]
+
+ OPTIONS:
+  -f, --face STRING                Which cow face to use (cow, tux). Default: cow.(valid: cow|tux)(default: cow)
+  -v, --version                    Print version.
+  -h, --help                       Print help information.
+#+end_example
+
+** Demo
+#+begin_src bash
+$ cowsay hi
+ ____
+< hi >
+ ----
+        \   ^__^
+         \  (oo)\_______
+            (__)\       )\/\
+                ||----w |
+                ||     ||
+
+$ cowsay -f tux hi
+ ____
+< hi >
+ ----
+   \
+    \
+        .--.
+       |o_o |
+       |:_/ |
+      //   \ \
+     (|     | )
+    /'\_   _/`\
+    \___)=(___/
+
+$ cowsay hello world
+ ___________
+< hello world >
+ -----------
+        \   ^__^
+         \  (oo)\_______
+            (__)\       )\/\
+                ||----w |
+                ||     ||
+#+end_src

src/bin/cowsay.zig

@@ -0,0 +1,190 @@
+//! Cowsay in Zig
+//! https://en.wikipedia.org/wiki/Cowsay
+
+const std = @import("std");
+const simargs = @import("simargs");
+const util = @import("util.zig");
+const mem = std.mem;
+const testing = std.testing;
+
+// The default ASCII cow art.
+const cow_art: []const u8 =
+    \\        \   ^__^
+    \\         \  (oo)\_______
+    \\            (__)\       )\/\
+    \\                ||----w |
+    \\                ||     ||
+    \\
+;
+
+// The Tux (Linux penguin) ASCII art.
+const tux_art: []const u8 =
+    \\   \
+    \\    \
+    \\        .--.
+    \\       |o_o |
+    \\       |:_/ |
+    \\      //   \ \
+    \\     (|     | )
+    \\    /'\_   _/`\
+    \\    \___)=(___/
+    \\
+;
+
+const CowFace = enum {
+    cow,
+    tux,
+};
+
+pub fn main() !void {
+    var gpa = util.Allocator.instance;
+    defer gpa.deinit();
+    const allocator = gpa.allocator();
+
+    const opt = try simargs.parse(allocator, struct {
+        face: CowFace = .cow,
+        help: bool = false,
+        version: bool = false,
+
+        pub const __shorts__ = .{
+            .face = .f,
+            .help = .h,
+            .version = .v,
+        };
+
+        pub const __messages__ = .{
+            .face = "Which cow face to use (cow, tux). Default: cow.",
+            .help = "Print help information.",
+            .version = "Print version.",
+        };
+    }, .{
+        .argument_prompt = "[message]",
+        .version_string = util.get_build_info(),
+    });
+    defer opt.deinit();
+
+    // Join all positional arguments with spaces to form the message.
+    var message_parts_buf: [4096]u8 = undefined;
+    const message: []const u8 = if (opt.positional_arguments.len == 0)
+        ""
+    else blk: {
+        var fbs = std.io.fixedBufferStream(&message_parts_buf);
+        const fbs_writer = fbs.writer();
+        for (opt.positional_arguments, 0..) |arg, i| {
+            if (i > 0) try fbs_writer.writeByte(' ');
+            try fbs_writer.writeAll(arg);
+        }
+        break :blk fbs.getWritten();
+    };
+
+    const stdout = std.fs.File.stdout();
+    var output_buf: [8192]u8 = undefined;
+    var writer = stdout.writer(&output_buf);
+
+    try writeSpeechBubble(&writer.interface, message);
+
+    const art = switch (opt.options.face) {
+        .cow => cow_art,
+        .tux => tux_art,
+    };
+    try writer.interface.writeAll(art);
+    try writer.interface.flush();
+}
+
+/// Renders a speech bubble around the given message to the writer.
+/// Single-line messages use `< text >` borders.
+/// Multi-line messages use `/`, `|`, `\` borders on the sides.
+fn writeSpeechBubble(writer: anytype, message: []const u8) !void {
+    // Collect lines and find the maximum line width.
+    var lines_buf: [64][]const u8 = undefined;
+    var line_count: usize = 0;
+    var max_width: usize = 0;
+
+    var iter = mem.splitScalar(u8, message, '\n');
+    while (iter.next()) |line| {
+        if (line_count >= lines_buf.len) break;
+        lines_buf[line_count] = line;
+        line_count += 1;
+        if (line.len > max_width) {
+            max_width = line.len;
+        }
+    }
+
+    const lines = lines_buf[0..line_count];
+    // The border width includes one space of padding on each side.
+    const border_width = max_width + 2;
+
+    // Write the top border: a space then `border_width` underscores.
+    try writer.writeAll(" ");
+    for (0..border_width) |_| try writer.writeAll("_");
+    try writer.writeAll("\n");
+
+    // Write message lines with box-drawing characters.
+    if (lines.len == 1) {
+        // Single line: use angle brackets.
+        try writer.writeAll("< ");
+        try writer.writeAll(lines[0]);
+        try writer.writeAll(" >\n");
+    } else {
+        for (lines, 0..) |line, i| {
+            const left = if (i == 0) "/ " else if (i == lines.len - 1) "\\ " else "| ";
+            const right = if (i == 0) " \\" else if (i == lines.len - 1) " /" else " |";
+            try writer.writeAll(left);
+            try writer.writeAll(line);
+            // Pad shorter lines to the maximum width so all borders align.
+            for (0..max_width - line.len) |_| try writer.writeAll(" ");
+            try writer.writeAll(right);
+            try writer.writeAll("\n");
+        }
+    }
+
+    // Write the bottom border: a space then `border_width` dashes.
+    try writer.writeAll(" ");
+    for (0..border_width) |_| try writer.writeAll("-");
+    try writer.writeAll("\n");
+}
+
+test "speech bubble single line" {
+    // A single-line message should use '< text >' delimiters.
+    var out: std.ArrayList(u8) = .empty;
+    defer out.deinit(testing.allocator);
+    try writeSpeechBubble(out.writer(testing.allocator), "hi");
+
+    try testing.expectEqualStrings(
+        \\ ____
+        \\< hi >
+        \\ ----
+        \\
+    , out.items);
+}
+
+test "speech bubble multi line" {
+    // A multi-line message should use '/', '|', '\' delimiters.
+    var out: std.ArrayList(u8) = .empty;
+    defer out.deinit(testing.allocator);
+    try writeSpeechBubble(out.writer(testing.allocator), "hello\nworld");
+
+    try testing.expectEqualStrings(
+        \\ _______
+        \\/ hello \
+        \\\ world /
+        \\ -------
+        \\
+    , out.items);
+}
+
+test "speech bubble three lines" {
+    // Middle lines should use '|' delimiters; first is '/', last is '\'.
+    var out: std.ArrayList(u8) = .empty;
+    defer out.deinit(testing.allocator);
+    try writeSpeechBubble(out.writer(testing.allocator), "one\ntwo\nthree");
+
+    try testing.expectEqualStrings(
+        \\ _______
+        \\/ one   \
+        \\| two   |
+        \\\ three /
+        \\ -------
+        \\
+    , out.items);
+}