| 🛟 Updated. 28d5985 k33g 12h ago | 1 | //go:build darwin |
| 2 | |
| 3 | package terminal |
| 4 | |
| 5 | import ( |
| 6 | "bytes" |
| 7 | "fmt" |
| 8 | "os" |
| 9 | "syscall" |
| 10 | "unsafe" |
| 11 | |
| 12 | "golang.org/x/sys/unix" |
| 13 | ) |
| 14 | |
| 15 | // openPTY allocates a pseudo-terminal and returns both of its ends. |
| 16 | // |
| 17 | // Darwin hands out the slave by name rather than by number: grant it, unlock |
| 18 | // it, then ask for the name. TIOCPTYGNAME writes into a buffer, and x/sys/unix |
| 19 | // exposes no helper for an ioctl of that shape — hence the one raw call below. |
| 20 | func openPTY() (master, slave *os.File, err error) { |
| 21 | master, err = os.OpenFile("/dev/ptmx", os.O_RDWR|unix.O_NOCTTY, 0) |
| 22 | if err != nil { |
| 23 | return nil, nil, fmt.Errorf("terminal: opening /dev/ptmx: %w", err) |
| 24 | } |
| 25 | |
| 26 | for _, step := range []struct { |
| 27 | request uint |
| 28 | what string |
| 29 | }{ |
| 30 | {unix.TIOCPTYGRANT, "granting"}, |
| 31 | {unix.TIOCPTYUNLK, "unlocking"}, |
| 32 | } { |
| 33 | if err := unix.IoctlSetInt(int(master.Fd()), step.request, 0); err != nil { |
| 34 | master.Close() |
| 35 | return nil, nil, fmt.Errorf("terminal: %s the pseudo-terminal: %w", step.what, err) |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | name, err := slaveName(master) |
| 40 | if err != nil { |
| 41 | master.Close() |
| 42 | return nil, nil, err |
| 43 | } |
| 44 | |
| 45 | slave, err = os.OpenFile(name, os.O_RDWR|unix.O_NOCTTY, 0) |
| 46 | if err != nil { |
| 47 | master.Close() |
| 48 | return nil, nil, fmt.Errorf("terminal: opening the slave side: %w", err) |
| 49 | } |
| 50 | return master, slave, nil |
| 51 | } |
| 52 | |
| 53 | // ptyNameLength is the size of the buffer TIOCPTYGNAME fills, as the request |
| 54 | // itself encodes. |
| 55 | const ptyNameLength = 128 |
| 56 | |
| 57 | // slaveName asks the kernel for the path of the slave device. |
| 58 | func slaveName(master *os.File) (string, error) { |
| 59 | var buffer [ptyNameLength]byte |
| 60 | |
| 61 | _, _, errno := syscall.Syscall( |
| 62 | syscall.SYS_IOCTL, |
| 63 | master.Fd(), |
| 64 | uintptr(unix.TIOCPTYGNAME), |
| 65 | uintptr(unsafe.Pointer(&buffer[0])), |
| 66 | ) |
| 67 | if errno != 0 { |
| 68 | return "", fmt.Errorf("terminal: naming the pseudo-terminal: %w", errno) |
| 69 | } |
| 70 | |
| 71 | // The kernel writes a C string, so the name ends at the first zero byte. |
| 72 | if end := bytes.IndexByte(buffer[:], 0); end >= 0 { |
| 73 | return string(buffer[:end]), nil |
| 74 | } |
| 75 | return string(buffer[:]), nil |
| 76 | } |
| 77 | |
| 78 | // setWinsize tells the pseudo-terminal how big it is, which the kernel passes |
| 79 | // on to the shell as SIGWINCH. |
| 80 | func setWinsize(master *os.File, width, height int) error { |
| 81 | return unix.IoctlSetWinsize(int(master.Fd()), unix.TIOCSWINSZ, &unix.Winsize{ |
| 82 | Row: uint16(height), |
| 83 | Col: uint16(width), |
| 84 | }) |
| 85 | } |
| 86 | |
| 87 | // childAttributes put the shell in a session of its own with the slave as its |
| 88 | // controlling terminal. |
| 89 | // |
| 90 | // Without this the shell has no controlling terminal, and job control — Ctrl-C, |
| 91 | // Ctrl-Z, running something in the background — does not work at all. |
| 92 | func childAttributes() *syscall.SysProcAttr { |
| 93 | return &syscall.SysProcAttr{Setsid: true, Setctty: true} |
| 94 | } |