On 2016-12-05 18:26, Wildman via Python-list wrote:
> On Mon, 05 Dec 2016 16:08:57 -0600, Tim Chase wrote:
>
> > On 2016-12-05 14:58, Wildman via Python-list wrote:
> >> I there a way to detect what the Linux runlevel is from
> >> within a Python program? I would like to be able to do
> >> it without the use of an external program such as 'who'
> >> or 'runlevel'.
> >
> > You can use something like
> >
> > https://gist.github.com/likexian/f9da722585036d372dca
> >
> > to parse the /var/run/utmp contents. Based on some source-code
> > scrounging, it looks like you want the first field to be "1" for
> > the "runlevel" account. To extract the actual runlevel, you can
> > take the PID value from the second column ("53" in my example
> > here) and take it's integer value mod 256 (AKA "& 0xff") to get
> > the character value. So chr(int("53") & 0xff) returns "5" in my
> > case, which is my runlevel.
> >
> > Additional links I found helpful while searching:
> >
> > https://casper.berkeley.edu/svn/trunk/roach/sw/busybox-1.10.1/miscutils/runlevel.c
> > https://github.com/garabik/python-utmp
>
> That is exactly the kind of thing I was looking for. Thank you.
> Now all I have to do is get it to work with Python3.
This works based on my poking at it in both Py2 and Py3:
import struct
from collections import namedtuple
try:
basestring
except NameError:
basestring = str
UTMP = namedtuple("UTMP", [
"ut_type", # Type of record
"ut_pid", # PID of login process
"ut_line", # Device name of tty - "/dev/"
"ut_id", # Terminal name suffix, or inittab(5) ID
"ut_user", # Username
"ut_host", # Hostname for remote login, or kernel version for run-level
messages
"e_termination", # Process termination status
"e_exit", # Process exit status
"ut_session", # Session ID (getsid(2)), used for windowing
"tv_sec", # Seconds
"tv_usec", # Microseconds
"ut_addr_v6a", # Internet address of remote host; IPv4 address uses just
ut_addr_v6[0]
"ut_addr_v6b", # Internet address of remote host; IPv4 address uses just
ut_addr_v6[0]
"ut_addr_v6c", # Internet address of remote host; IPv4 address uses just
ut_addr_v6[0]
"ut_addr_v6d", # Internet address of remote host; IPv4 address uses just
ut_addr_v6[0]
#"__unused", # Reserved for future use
])
XTMP_STRUCT = "hi32s4s32s256shhiiiiiii20x"
XTMP_STRUCT_SIZE = struct.calcsize(XTMP_STRUCT)
# ut_types
EMPTY = 0
RUN_LVL = 1
BOOT_TIME = 2
OLD_TIME = 3
NEW_TIME = 4
INIT_PROCESS = 5 # Process spawned by "init"
LOGIN_PROCESS = 6 # A "getty" process
DEFAULT_UTMP = "/var/run/utmp"
def parse_utmp(utmp_fname=DEFAULT_UTMP):
with open(utmp_fname, "rb") as f:
while True:
bytes = f.read(XTMP_STRUCT_SIZE)
if not bytes:
break
bits = struct.unpack(XTMP_STRUCT, bytes)
bits = [
bit.rstrip('\0') if isinstance(bit, basestring) else bit
for bit
in bits
]
yield UTMP(*bits)
def filter(ut_type, utmp_fname=DEFAULT_UTMP):
for utmp in parse_utmp(utmp_fname):
if utmp.ut_type == ut_type:
yield utmp
def get_runlevel(utmp_fname=DEFAULT_UTMP):
return chr(next(filter(RUN_LVL, utmp_fname)).ut_pid & 0xFF)
if __name__ == "__main__":
print("Runlevel: %s" % get_runlevel())
-tkc
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