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More pyparsing and DHCP hosts

Since I wrote my original pyparsing post a few days ago, I've done some more work on refining my ISC dhcpd.conf host parsing example program. I also received some useful comments and suggests from Paul McGuire, the author the pyparsing module (thanks, Paul!), which I have also tried to incorporate.

It's it's currently just a useless toy program but it is starting to look quite pretty.


#!/usr/bin/python

from pyparsing import *

# An few host entries from dhcpd.conf
sample_data = """

# A host with dynamic DNS attributes
host a.foo.bar {
   ddns-hostname a;
   ddns-domainname "foo.bar";
   hardware ethernet 00:11:22:33:44:55;
   fixed-address 192.168.100.10, 192.168.200.50;
}

# A simple multi-line host
host b.foo.bar {
   hardware ethernet 00:0f:12:34:56:78;
   fixed-address 192.168.100.20;
}

# A simple single-line host
host c.foo.bar { hardware ethernet 00:0e:12:34:50:70; fixed-address 192.168.100.40; }
"""

digits = "0123456789"
colon,semi,period,comma,lbrace,rbrace,quote = map(Literal,':;.,{}"')
number = Word(digits)
hexint = Word(hexnums,exact=2)
dnschars = Word(alphanums + '-') # characters permissible in DNS names

mac = Combine(hexint + (":" + hexint) * 5)("mac_address")
ip = Combine(number + period + number + period + number + period + number)
ips = delimitedList(ip)("ip_addresses")
hardware_ethernet  = Literal('hardware') + Literal('ethernet') + mac + semi
hostname = dnschars
domainname = dnschars + OneOrMore("." + dnschars)
fqdn = Combine(hostname + period + domainname)("fqdn")

fixed_address  = Literal('fixed-address') + ips + semi
ddns_hostname = Literal('ddns-hostname') + hostname + semi
ddns_domainname = Literal('ddns-domainname') + quote + domainname + quote + semi

# Put the grammar together to define a host declaration
host = Literal('host') + fqdn + lbrace + Optional(ddns_hostname) + Optional(ddns_domainname) + Optional(hardware_ethernet) + Optional(fixed_address) + rbrace

results = host.scanString(sample_data)

for result in results:
 print result[0].fqdn, result[0].mac_address , result[0].ip_addresses

file.close()


The output is still the same as that of the original program.

If you want it to read your sample data from a file, just change the following line:


results = host.scanString(sample_data)


... to:


filename = "/etc/dhcp3/dhcpd.conf"
file = open(filename, "rb")
results = host.scanString("".join(file.readlines()))
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