zig/example/cat/main.zig
Andrew Kelley ec1b6f6673
breaking syntax change: ??x to x.? (#1095)
See #1023

This also renames Nullable/Maybe to Optional
2018-06-09 23:42:14 -04:00

70 lines
1.9 KiB
Zig

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;
};
}