ptyshell.py 文件源码

def spawn(self, argv=None, term=None):
        if argv is None:
            if 'SHELL' in os.environ:
                argv = [os.environ['SHELL']]
            elif 'PATH' in os.environ: #searching sh in the path. It can be unusual like /system/bin/sh on android
                for shell in ["bash","sh","ksh","zsh","csh","ash"]:
                    for path in os.environ['PATH'].split(':'):
                        fullpath=os.path.join(path.strip(),shell)
                        if os.path.isfile(fullpath):
                            argv=[fullpath]
                            break
                    if argv:
                        break
        if not argv:
            argv= ['/bin/sh']

        if term is not None:
            os.environ['TERM']=term

        master, slave = pty.openpty()
        self.slave=slave
        self.master = os.fdopen(master, 'rb+wb', 0) # open file in an unbuffered mode
        flags = fcntl.fcntl(self.master, fcntl.F_GETFL)
        assert flags>=0
        flags = fcntl.fcntl(self.master, fcntl.F_SETFL , flags | os.O_NONBLOCK)
        assert flags>=0
        self.prog = subprocess.Popen(
            shell=False,
            args=argv,
            stdin=slave,
            stdout=slave,
            stderr=subprocess.STDOUT,
            preexec_fn=prepare
        )