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- pexpect.ExceptionPexpect(exceptions.Exception)
-
- ExceptionPxssh
- pexpect.spawn(__builtin__.object)
-
- pxssh
class pxssh(pexpect.spawn) |
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This class extends pexpect.spawn to specialize setting up SSH
connections. This adds methods for login, logout, and expecting the shell
prompt. It does various tricky things to handle many situations in the SSH
login process. For example, if the session is your first login, then pxssh
automatically accepts the remote certificate; or if you have public key
authentication setup then pxssh won't wait for the password prompt.
pxssh uses the shell prompt to synchronize output from the remote host. In
order to make this more robust it sets the shell prompt to something more
unique than just $ or #. This should work on most Borne/Bash or Csh style
shells.
Example that runs a few commands on a remote server and prints the result::
import pxssh
import getpass
try:
s = pxssh.pxssh()
hostname = raw_input('hostname: ')
username = raw_input('username: ')
password = getpass.getpass('password: ')
s.login (hostname, username, password)
s.sendline ('uptime') # run a command
s.prompt() # match the prompt
print s.before # print everything before the prompt.
s.sendline ('ls -l')
s.prompt()
print s.before
s.sendline ('df')
s.prompt()
print s.before
s.logout()
except pxssh.ExceptionPxssh, e:
print "pxssh failed on login."
print str(e)
Note that if you have ssh-agent running while doing development with pxssh
then this can lead to a lot of confusion. Many X display managers (xdm,
gdm, kdm, etc.) will automatically start a GUI agent. You may see a GUI
dialog box popup asking for a password during development. You should turn
off any key agents during testing. The 'force_password' attribute will turn
off public key authentication. This will only work if the remote SSH server
is configured to allow password logins. Example of using 'force_password'
attribute::
s = pxssh.pxssh()
s.force_password = True
hostname = raw_input('hostname: ')
username = raw_input('username: ')
password = getpass.getpass('password: ')
s.login (hostname, username, password)
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- Method resolution order:
- pxssh
- pexpect.spawn
- __builtin__.object
Methods defined here:
- __init__(self, timeout=30, maxread=2000, searchwindowsize=None, logfile=None, cwd=None, env=None)
- levenshtein_distance(self, a, b)
- This calculates the Levenshtein distance between a and b.
- login(self, server, username, password='', terminal_type='ansi', original_prompt='[#$]', login_timeout=10, port=None, auto_prompt_reset=True)
- This logs the user into the given server. It uses the
'original_prompt' to try to find the prompt right after login. When it
finds the prompt it immediately tries to reset the prompt to something
more easily matched. The default 'original_prompt' is very optimistic
and is easily fooled. It's more reliable to try to match the original
prompt as exactly as possible to prevent false matches by server
strings such as the "Message Of The Day". On many systems you can
disable the MOTD on the remote server by creating a zero-length file
called "~/.hushlogin" on the remote server. If a prompt cannot be found
then this will not necessarily cause the login to fail. In the case of
a timeout when looking for the prompt we assume that the original
prompt was so weird that we could not match it, so we use a few tricks
to guess when we have reached the prompt. Then we hope for the best and
blindly try to reset the prompt to something more unique. If that fails
then login() raises an ExceptionPxssh exception.
In some situations it is not possible or desirable to reset the
original prompt. In this case, set 'auto_prompt_reset' to False to
inhibit setting the prompt to the UNIQUE_PROMPT. Remember that pxssh
uses a unique prompt in the prompt() method. If the original prompt is
not reset then this will disable the prompt() method unless you
manually set the PROMPT attribute.
- logout(self)
- This sends exit to the remote shell. If there are stopped jobs then
this automatically sends exit twice.
- prompt(self, timeout=20)
- This matches the shell prompt. This is little more than a short-cut
to the expect() method. This returns True if the shell prompt was
matched. This returns False if there was a timeout. Note that if you
called login() with auto_prompt_reset set to False then you should have
manually set the PROMPT attribute to a regex pattern for matching the
prompt.
- set_unique_prompt(self)
- This sets the remote prompt to something more unique than # or $.
This makes it easier for the prompt() method to match the shell prompt
unambiguously. This method is called automatically by the login()
method, but you may want to call it manually if you somehow reset the
shell prompt. For example, if you 'su' to a different user then you
will need to manually reset the prompt. This sends shell commands to
the remote host to set the prompt, so this assumes the remote host is
ready to receive commands.
Alternatively, you may use your own prompt pattern. Just set the PROMPT
attribute to a regular expression that matches it. In this case you
should call login() with auto_prompt_reset=False; then set the PROMPT
attribute. After that the prompt() method will try to match your prompt
pattern.
- synch_original_prompt(self)
- This attempts to find the prompt. Basically, press enter and record
the response; press enter again and record the response; if the two
responses are similar then assume we are at the original prompt.
Methods inherited from pexpect.spawn:
- __del__(self)
- This makes sure that no system resources are left open. Python only
garbage collects Python objects. OS file descriptors are not Python
objects, so they must be handled explicitly. If the child file
descriptor was opened outside of this class (passed to the constructor)
then this does not close it.
- __iter__(self)
- This is to support iterators over a file-like object.
- __str__(self)
- This returns a human-readable string that represents the state of
the object.
- close(self, force=True)
- This closes the connection with the child application. Note that
calling close() more than once is valid. This emulates standard Python
behavior with files. Set force to True if you want to make sure that
the child is terminated (SIGKILL is sent if the child ignores SIGHUP
and SIGINT).
- compile_pattern_list(self, patterns)
- This compiles a pattern-string or a list of pattern-strings.
Patterns must be a StringType, EOF, TIMEOUT, SRE_Pattern, or a list of
those. Patterns may also be None which results in an empty list (you
might do this if waiting for an EOF or TIMEOUT condition without
expecting any pattern).
This is used by expect() when calling expect_list(). Thus expect() is
nothing more than::
cpl = compile_pattern_list(pl)
return expect_list(cpl, timeout)
If you are using expect() within a loop it may be more
efficient to compile the patterns first and then call expect_list().
This avoid calls in a loop to compile_pattern_list()::
cpl = compile_pattern_list(my_pattern)
while some_condition:
...
i = expect_list(clp, timeout)
...
- eof(self)
- This returns True if the EOF exception was ever raised.
- expect(self, pattern, timeout=-1, searchwindowsize=None)
- This seeks through the stream until a pattern is matched. The
pattern is overloaded and may take several types. The pattern can be a
StringType, EOF, a compiled re, or a list of any of those types.
Strings will be compiled to re types. This returns the index into the
pattern list. If the pattern was not a list this returns index 0 on a
successful match. This may raise exceptions for EOF or TIMEOUT. To
avoid the EOF or TIMEOUT exceptions add EOF or TIMEOUT to the pattern
list. That will cause expect to match an EOF or TIMEOUT condition
instead of raising an exception.
If you pass a list of patterns and more than one matches, the first match
in the stream is chosen. If more than one pattern matches at that point,
the leftmost in the pattern list is chosen. For example::
# the input is 'foobar'
index = p.expect (['bar', 'foo', 'foobar'])
# returns 1 ('foo') even though 'foobar' is a "better" match
Please note, however, that buffering can affect this behavior, since
input arrives in unpredictable chunks. For example::
# the input is 'foobar'
index = p.expect (['foobar', 'foo'])
# returns 0 ('foobar') if all input is available at once,
# but returs 1 ('foo') if parts of the final 'bar' arrive late
After a match is found the instance attributes 'before', 'after' and
'match' will be set. You can see all the data read before the match in
'before'. You can see the data that was matched in 'after'. The
re.MatchObject used in the re match will be in 'match'. If an error
occurred then 'before' will be set to all the data read so far and
'after' and 'match' will be None.
If timeout is -1 then timeout will be set to the self.timeout value.
A list entry may be EOF or TIMEOUT instead of a string. This will
catch these exceptions and return the index of the list entry instead
of raising the exception. The attribute 'after' will be set to the
exception type. The attribute 'match' will be None. This allows you to
write code like this::
index = p.expect (['good', 'bad', pexpect.EOF, pexpect.TIMEOUT])
if index == 0:
do_something()
elif index == 1:
do_something_else()
elif index == 2:
do_some_other_thing()
elif index == 3:
do_something_completely_different()
instead of code like this::
try:
index = p.expect (['good', 'bad'])
if index == 0:
do_something()
elif index == 1:
do_something_else()
except EOF:
do_some_other_thing()
except TIMEOUT:
do_something_completely_different()
These two forms are equivalent. It all depends on what you want. You
can also just expect the EOF if you are waiting for all output of a
child to finish. For example::
p = pexpect.spawn('/bin/ls')
p.expect (pexpect.EOF)
print p.before
If you are trying to optimize for speed then see expect_list().
- expect_exact(self, pattern_list, timeout=-1, searchwindowsize=-1)
- This is similar to expect(), but uses plain string matching instead
of compiled regular expressions in 'pattern_list'. The 'pattern_list'
may be a string; a list or other sequence of strings; or TIMEOUT and
EOF.
This call might be faster than expect() for two reasons: string
searching is faster than RE matching and it is possible to limit the
search to just the end of the input buffer.
This method is also useful when you don't want to have to worry about
escaping regular expression characters that you want to match.
- expect_list(self, pattern_list, timeout=-1, searchwindowsize=-1)
- This takes a list of compiled regular expressions and returns the
index into the pattern_list that matched the child output. The list may
also contain EOF or TIMEOUT (which are not compiled regular
expressions). This method is similar to the expect() method except that
expect_list() does not recompile the pattern list on every call. This
may help if you are trying to optimize for speed, otherwise just use
the expect() method. This is called by expect(). If timeout==-1 then
the self.timeout value is used. If searchwindowsize==-1 then the
self.searchwindowsize value is used.
- expect_loop(self, searcher, timeout=-1, searchwindowsize=-1)
- This is the common loop used inside expect. The 'searcher' should be
an instance of searcher_re or searcher_string, which describes how and what
to search for in the input.
See expect() for other arguments, return value and exceptions.
- fileno(self)
- This returns the file descriptor of the pty for the child.
- flush(self)
- This does nothing. It is here to support the interface for a
File-like object.
- getecho(self)
- This returns the terminal echo mode. This returns True if echo is
on or False if echo is off. Child applications that are expecting you
to enter a password often set ECHO False. See waitnoecho().
- getwinsize(self)
- This returns the terminal window size of the child tty. The return
value is a tuple of (rows, cols).
- interact(self, escape_character='\x1d', input_filter=None, output_filter=None)
- This gives control of the child process to the interactive user (the
human at the keyboard). Keystrokes are sent to the child process, and
the stdout and stderr output of the child process is printed. This
simply echos the child stdout and child stderr to the real stdout and
it echos the real stdin to the child stdin. When the user types the
escape_character this method will stop. The default for
escape_character is ^]. This should not be confused with ASCII 27 --
the ESC character. ASCII 29 was chosen for historical merit because
this is the character used by 'telnet' as the escape character. The
escape_character will not be sent to the child process.
You may pass in optional input and output filter functions. These
functions should take a string and return a string. The output_filter
will be passed all the output from the child process. The input_filter
will be passed all the keyboard input from the user. The input_filter
is run BEFORE the check for the escape_character.
Note that if you change the window size of the parent the SIGWINCH
signal will not be passed through to the child. If you want the child
window size to change when the parent's window size changes then do
something like the following example::
import pexpect, struct, fcntl, termios, signal, sys
def sigwinch_passthrough (sig, data):
s = struct.pack("HHHH", 0, 0, 0, 0)
a = struct.unpack('hhhh', fcntl.ioctl(sys.stdout.fileno(), termios.TIOCGWINSZ , s))
global p
p.setwinsize(a[0],a[1])
p = pexpect.spawn('/bin/bash') # Note this is global and used in sigwinch_passthrough.
signal.signal(signal.SIGWINCH, sigwinch_passthrough)
p.interact()
- isalive(self)
- This tests if the child process is running or not. This is
non-blocking. If the child was terminated then this will read the
exitstatus or signalstatus of the child. This returns True if the child
process appears to be running or False if not. It can take literally
SECONDS for Solaris to return the right status.
- isatty(self)
- This returns True if the file descriptor is open and connected to a
tty(-like) device, else False.
- kill(self, sig)
- This sends the given signal to the child application. In keeping
with UNIX tradition it has a misleading name. It does not necessarily
kill the child unless you send the right signal.
- next(self)
- This is to support iterators over a file-like object.
- read(self, size=-1)
- This reads at most "size" bytes from the file (less if the read hits
EOF before obtaining size bytes). If the size argument is negative or
omitted, read all data until EOF is reached. The bytes are returned as
a string object. An empty string is returned when EOF is encountered
immediately.
- read_nonblocking(self, size=1, timeout=-1)
- This reads at most size characters from the child application. It
includes a timeout. If the read does not complete within the timeout
period then a TIMEOUT exception is raised. If the end of file is read
then an EOF exception will be raised. If a log file was set using
setlog() then all data will also be written to the log file.
If timeout is None then the read may block indefinitely. If timeout is -1
then the self.timeout value is used. If timeout is 0 then the child is
polled and if there was no data immediately ready then this will raise
a TIMEOUT exception.
The timeout refers only to the amount of time to read at least one
character. This is not effected by the 'size' parameter, so if you call
read_nonblocking(size=100, timeout=30) and only one character is
available right away then one character will be returned immediately.
It will not wait for 30 seconds for another 99 characters to come in.
This is a wrapper around os.read(). It uses select.select() to
implement the timeout.
- readline(self, size=-1)
- This reads and returns one entire line. A trailing newline is kept
in the string, but may be absent when a file ends with an incomplete
line. Note: This readline() looks for a \r\n pair even on UNIX
because this is what the pseudo tty device returns. So contrary to what
you may expect you will receive the newline as \r\n. An empty string
is returned when EOF is hit immediately. Currently, the size argument is
mostly ignored, so this behavior is not standard for a file-like
object. If size is 0 then an empty string is returned.
- readlines(self, sizehint=-1)
- This reads until EOF using readline() and returns a list containing
the lines thus read. The optional "sizehint" argument is ignored.
- send(self, s)
- This sends a string to the child process. This returns the number of
bytes written. If a log file was set then the data is also written to
the log.
- sendcontrol(self, char)
- This sends a control character to the child such as Ctrl-C or
Ctrl-D. For example, to send a Ctrl-G (ASCII 7)::
child.sendcontrol('g')
See also, sendintr() and sendeof().
- sendeof(self)
- This sends an EOF to the child. This sends a character which causes
the pending parent output buffer to be sent to the waiting child
program without waiting for end-of-line. If it is the first character
of the line, the read() in the user program returns 0, which signifies
end-of-file. This means to work as expected a sendeof() has to be
called at the beginning of a line. This method does not send a newline.
It is the responsibility of the caller to ensure the eof is sent at the
beginning of a line.
- sendintr(self)
- This sends a SIGINT to the child. It does not require
the SIGINT to be the first character on a line.
- sendline(self, s='')
- This is like send(), but it adds a line feed (os.linesep). This
returns the number of bytes written.
- setecho(self, state)
- This sets the terminal echo mode on or off. Note that anything the
child sent before the echo will be lost, so you should be sure that
your input buffer is empty before you call setecho(). For example, the
following will work as expected::
p = pexpect.spawn('cat')
p.sendline ('1234') # We will see this twice (once from tty echo and again from cat).
p.expect (['1234'])
p.expect (['1234'])
p.setecho(False) # Turn off tty echo
p.sendline ('abcd') # We will set this only once (echoed by cat).
p.sendline ('wxyz') # We will set this only once (echoed by cat)
p.expect (['abcd'])
p.expect (['wxyz'])
The following WILL NOT WORK because the lines sent before the setecho
will be lost::
p = pexpect.spawn('cat')
p.sendline ('1234') # We will see this twice (once from tty echo and again from cat).
p.setecho(False) # Turn off tty echo
p.sendline ('abcd') # We will set this only once (echoed by cat).
p.sendline ('wxyz') # We will set this only once (echoed by cat)
p.expect (['1234'])
p.expect (['1234'])
p.expect (['abcd'])
p.expect (['wxyz'])
- setlog(self, fileobject)
- This method is no longer supported or allowed.
- setmaxread(self, maxread)
- This method is no longer supported or allowed. I don't like getters
and setters without a good reason.
- setwinsize(self, r, c)
- This sets the terminal window size of the child tty. This will cause
a SIGWINCH signal to be sent to the child. This does not change the
physical window size. It changes the size reported to TTY-aware
applications like vi or curses -- applications that respond to the
SIGWINCH signal.
- terminate(self, force=False)
- This forces a child process to terminate. It starts nicely with
SIGHUP and SIGINT. If "force" is True then moves onto SIGKILL. This
returns True if the child was terminated. This returns False if the
child could not be terminated.
- wait(self)
- This waits until the child exits. This is a blocking call. This will
not read any data from the child, so this will block forever if the
child has unread output and has terminated. In other words, the child
may have printed output then called exit(); but, technically, the child
is still alive until its output is read.
- waitnoecho(self, timeout=-1)
- This waits until the terminal ECHO flag is set False. This returns
True if the echo mode is off. This returns False if the ECHO flag was
not set False before the timeout. This can be used to detect when the
child is waiting for a password. Usually a child application will turn
off echo mode when it is waiting for the user to enter a password. For
example, instead of expecting the "password:" prompt you can wait for
the child to set ECHO off::
p = pexpect.spawn ('ssh user@example.com')
p.waitnoecho()
p.sendline(mypassword)
If timeout is None then this method to block forever until ECHO flag is
False.
- write(self, s)
- This is similar to send() except that there is no return value.
- writelines(self, sequence)
- This calls write() for each element in the sequence. The sequence
can be any iterable object producing strings, typically a list of
strings. This does not add line separators There is no return value.
Data descriptors inherited from pexpect.spawn:
- __dict__
- dictionary for instance variables (if defined)
- __weakref__
- list of weak references to the object (if defined)
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