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various tools I have been using throughout the years
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signals.zig (2007B)

      1 const std = @import("std");
      2 const builtin = @import("builtin");
      3 
      4 var signal_pipe: [2]std.posix.fd_t = undefined;
      5 
      6 fn signalHandler(sig: i32) callconv(.c) void {
      7     const s: i32 = sig;
      8     _ = std.c.write(signal_pipe[1], std.mem.asBytes(&s), @sizeOf(i32));
      9 }
     10 
     11 pub fn open() !std.Io.File {
     12     if (builtin.os.tag == .linux) {
     13         var mask = std.posix.sigemptyset();
     14         std.posix.sigaddset(&mask, std.posix.SIG.USR1);
     15         std.posix.sigaddset(&mask, std.posix.SIG.USR2);
     16 
     17         std.posix.sigprocmask(std.posix.SIG.BLOCK, &mask, null);
     18 
     19         const fd = try std.posix.signalfd(-1, &mask, std.os.linux.SFD.NONBLOCK);
     20         return .{ .handle = fd, .flags = .{ .nonblocking = false } };
     21     } else {
     22         const rc = std.c.pipe(&signal_pipe);
     23         switch (std.posix.errno(@intCast(rc))) {
     24             .SUCCESS => {},
     25             else => |err| return std.posix.unexpectedErrno(err),
     26         }
     27 
     28         const sa = std.posix.Sigaction{
     29             .handler = .{ .handler = signalHandler },
     30             .mask = std.posix.sigemptyset(),
     31             .flags = 0,
     32         };
     33 
     34         std.posix.sigaction(std.posix.SIG.USR1, &sa, null);
     35         std.posix.sigaction(std.posix.SIG.USR2, &sa, null);
     36 
     37         return .{ .handle = signal_pipe[0], .flags = .{ .nonblocking = false } };
     38     }
     39 }
     40 
     41 pub fn readSignal(fd: std.posix.fd_t) !std.posix.SIG {
     42     if (builtin.os.tag == .linux) {
     43         var buf: [@sizeOf(std.os.linux.signalfd_siginfo)]u8 align(@alignOf(std.os.linux.signalfd_siginfo)) = undefined;
     44         const n = try std.posix.read(fd, &buf);
     45         if (n == 0) return error.Unexpected;
     46         const siginfo: *const std.os.linux.signalfd_siginfo = @ptrCast(@alignCast(&buf));
     47         return @enumFromInt(siginfo.signo);
     48     } else {
     49         var buf: [4]u8 = undefined;
     50         const n = try std.posix.read(fd, &buf);
     51         if (n < 4) return error.Unexpected;
     52         var result: i32 = undefined;
     53         @memcpy(std.mem.asBytes(&result), &buf);
     54         return @enumFromInt(result);
     55     }
     56 }