Back to main.zig
We left our main function in this state:
pub fn main() !void {
var da = std.heap.DebugAllocator(.{}){};
defer _ = da.deinit();
const allocator = switch (builtin.mode) {
.Debug => da.allocator(),
else => std.heap.smp_allocator,
};
_ = allocator;
var buf: [1]u8 = undefined;
while (try readChar(&buf) == 1 and buf[0] != 'q') {}
}
Now we want to enable raw mode, right? And it's the first thing that our main function will do. Add these lines at the top of it:
pub fn main() !void {
orig_termios = try linux.enableRawMode();
defer linux.disableRawMode(orig_termios);
The defer statement is important because we want to restore the original
configuration when the program exits. We also want to update the bottom section
with our new variables. Add this at the bottom of the file:
const linux = @import("linux.zig");
var orig_termios: std.os.linux.termios = undefined;
When variables and constants are placed at the root level of a file, that is,
outside any functions, they behave like static identifiers in C, only visible
to the code of the current file, unless they have the pub qualifier, meaning
they can be accessed from files that import the current one.
Moreover, if the module is meant to be instantiated (it has fields defined at the root level), these variable and constants are, again, static, not part of the instances: all instances will share the same value, which is quite obvious for constants, less so for variables.
Why is it important to define orig_termios at the root level? Because we want
to handle another case: our program crashes, and we don't want to leave the
terminal in an unusable state if that happens. We'll have to update our crash
handler as well:
/// Our panic handler disables terminal raw mode and calls the default panic
/// handler.
fn crashed(msg: []const u8, trace: ?usize) noreturn {
linux.disableRawMode(orig_termios);
As you can see, also this function needs to access the original terminal configuration, and there's no way to pass it with an argument, it must read it from a variable.
Now, if you try to build and run the project, something strange happens: the program terminates immediately.