35.8.pty — Pseudo-terminal utilities¶

Source code:Lib/pty.py

Thepty module defines operations for handling the pseudo-terminalconcept: starting another process and being able to write to and read from itscontrolling terminal programmatically.

Because pseudo-terminal handling is highly platform dependent, there is code todo it only for Linux. (The Linux code is supposed to work on other platforms,but hasn’t been tested yet.)

Thepty module defines the following functions:

pty.fork()¶

Fork. Connect the child’s controlling terminal to a pseudo-terminal. Returnvalue is(pid,fd). Note that the child getspid 0, and thefd isinvalid. The parent’s return value is thepid of the child, andfd is afile descriptor connected to the child’s controlling terminal (and also to thechild’s standard input and output).

pty.openpty()¶

Open a new pseudo-terminal pair, usingos.openpty() if possible, oremulation code for generic Unix systems. Return a pair of file descriptors(master,slave), for the master and the slave end, respectively.

pty.spawn(argv[,master_read[,stdin_read]])¶

Spawn a process, and connect its controlling terminal with the currentprocess’s standard io. This is often used to baffle programs which insist onreading from the controlling terminal.

The functionsmaster_read andstdin_read should be functions which read froma file descriptor. The defaults try to read 1024 bytes each time they arecalled.

Changed in version 3.4:spawn() now returns the status value fromos.waitpid()on the child process.

importargparseimportosimportptyimportsysimporttimeparser=argparse.ArgumentParser()parser.add_argument('-a',dest='append',action='store_true')parser.add_argument('-p',dest='use_python',action='store_true')parser.add_argument('filename',nargs='?',default='typescript')options=parser.parse_args()shell=sys.executableifoptions.use_pythonelseos.environ.get('SHELL','sh')filename=options.filenamemode='ab'ifoptions.appendelse'wb'withopen(filename,mode)asscript:defread(fd):data=os.read(fd,1024)script.write(data)returndataprint('Script started, file is',filename)script.write(('Script started on%s\n'%time.asctime()).encode())pty.spawn(shell,read)script.write(('Script done on%s\n'%time.asctime()).encode())print('Script done, file is',filename)