1:mod:`pty` --- Pseudo-terminal utilities 2======================================== 3 4.. module:: pty 5 :platform: Unix 6 :synopsis: Pseudo-Terminal Handling for Unix. 7 8.. moduleauthor:: Steen Lumholt 9.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il> 10 11**Source code:** :source:`Lib/pty.py` 12 13-------------- 14 15The :mod:`pty` module defines operations for handling the pseudo-terminal 16concept: starting another process and being able to write to and read from its 17controlling terminal programmatically. 18 19Pseudo-terminal handling is highly platform dependent. This code is mainly 20tested on Linux, FreeBSD, and macOS (it is supposed to work on other POSIX 21platforms but it's not been thoroughly tested). 22 23The :mod:`pty` module defines the following functions: 24 25 26.. function:: fork() 27 28 Fork. Connect the child's controlling terminal to a pseudo-terminal. Return 29 value is ``(pid, fd)``. Note that the child gets *pid* 0, and the *fd* is 30 *invalid*. The parent's return value is the *pid* of the child, and *fd* is a 31 file descriptor connected to the child's controlling terminal (and also to the 32 child's standard input and output). 33 34 35.. function:: openpty() 36 37 Open a new pseudo-terminal pair, using :func:`os.openpty` if possible, or 38 emulation code for generic Unix systems. Return a pair of file descriptors 39 ``(master, slave)``, for the master and the slave end, respectively. 40 41 42.. function:: spawn(argv[, master_read[, stdin_read]]) 43 44 Spawn a process, and connect its controlling terminal with the current 45 process's standard io. This is often used to baffle programs which insist on 46 reading from the controlling terminal. It is expected that the process 47 spawned behind the pty will eventually terminate, and when it does *spawn* 48 will return. 49 50 A loop copies STDIN of the current process to the child and data received 51 from the child to STDOUT of the current process. It is not signaled to the 52 child if STDIN of the current process closes down. 53 54 The functions *master_read* and *stdin_read* are passed a file descriptor 55 which they should read from, and they should always return a byte string. In 56 order to force spawn to return before the child process exits an 57 empty byte array should be returned to signal end of file. 58 59 The default implementation for both functions will read and return up to 1024 60 bytes each time the function is called. The *master_read* callback is passed 61 the pseudoterminal’s master file descriptor to read output from the child 62 process, and *stdin_read* is passed file descriptor 0, to read from the 63 parent process's standard input. 64 65 Returning an empty byte string from either callback is interpreted as an 66 end-of-file (EOF) condition, and that callback will not be called after 67 that. If *stdin_read* signals EOF the controlling terminal can no longer 68 communicate with the parent process OR the child process. Unless the child 69 process will quit without any input, *spawn* will then loop forever. If 70 *master_read* signals EOF the same behavior results (on linux at least). 71 72 Return the exit status value from :func:`os.waitpid` on the child process. 73 74 :func:`waitstatus_to_exitcode` can be used to convert the exit status into 75 an exit code. 76 77 .. audit-event:: pty.spawn argv pty.spawn 78 79 .. versionchanged:: 3.4 80 :func:`spawn` now returns the status value from :func:`os.waitpid` 81 on the child process. 82 83Example 84------- 85 86.. sectionauthor:: Steen Lumholt 87 88The following program acts like the Unix command :manpage:`script(1)`, using a 89pseudo-terminal to record all input and output of a terminal session in a 90"typescript". :: 91 92 import argparse 93 import os 94 import pty 95 import sys 96 import time 97 98 parser = argparse.ArgumentParser() 99 parser.add_argument('-a', dest='append', action='store_true') 100 parser.add_argument('-p', dest='use_python', action='store_true') 101 parser.add_argument('filename', nargs='?', default='typescript') 102 options = parser.parse_args() 103 104 shell = sys.executable if options.use_python else os.environ.get('SHELL', 'sh') 105 filename = options.filename 106 mode = 'ab' if options.append else 'wb' 107 108 with open(filename, mode) as script: 109 def read(fd): 110 data = os.read(fd, 1024) 111 script.write(data) 112 return data 113 114 print('Script started, file is', filename) 115 script.write(('Script started on %s\n' % time.asctime()).encode()) 116 117 pty.spawn(shell, read) 118 119 script.write(('Script done on %s\n' % time.asctime()).encode()) 120 print('Script done, file is', filename) 121