const std = @import("std"); const io = std.io; const mem = std.mem; const os = std.os; const warn = std.debug.warn; const allocator = std.debug.global_allocator; pub fn main() !void { var args_it = os.args(); const exe = try unwrapArg(args_it.next(allocator).?); var catted_anything = false; var stdout_file = try io.getStdOut(); while (args_it.next(allocator)) |arg_or_err| { const arg = try unwrapArg(arg_or_err); if (mem.eql(u8, arg, "-")) { catted_anything = true; var stdin_file = try io.getStdIn(); try cat_file(&stdout_file, &stdin_file); } else if (arg[0] == '-') { return usage(exe); } else { var file = os.File.openRead(allocator, arg) catch |err| { warn("Unable to open file: {}\n", @errorName(err)); return err; }; defer file.close(); catted_anything = true; try cat_file(&stdout_file, &file); } } if (!catted_anything) { var stdin_file = try io.getStdIn(); try cat_file(&stdout_file, &stdin_file); } } fn usage(exe: []const u8) !void { warn("Usage: {} [FILE]...\n", exe); return error.Invalid; } fn cat_file(stdout: *os.File, file: *os.File) !void { var buf: [1024 * 4]u8 = undefined; while (true) { const bytes_read = file.read(buf[0..]) catch |err| { warn("Unable to read from stream: {}\n", @errorName(err)); return err; }; if (bytes_read == 0) { break; } stdout.write(buf[0..bytes_read]) catch |err| { warn("Unable to write to stdout: {}\n", @errorName(err)); return err; }; } } fn unwrapArg(arg: error![]u8) ![]u8 { return arg catch |err| { warn("Unable to parse command line: {}\n", err); return err; }; }