grepcidr 1.3 - Filter IP addresses matching IPv4 CIDR specification
Copyright (C) 2004-2005  Jem E. Berkes <jberkes@pc-tools.net>
	http://www.pc-tools.net/unix/grepcidr/
	http://www.sysdesign.ca/


PURPOSE
-------
grepcidr can be used to filter a list of IP addresses against one or more
Classless Inter-Domain Routing (CIDR) specifications, or arbitrary networks
specified by an address range. As with grep, there are options to invert
matching and load patterns from a file. grepcidr is capable of comparing
thousands or even millions of IPs to networks with little memory usage and
in reasonable computation time.

grepcidr has endless uses in network software, including: mail filtering and
processing, network security, log analysis, and many custom applications.

Many thanks to Dick Wesseling <ftu@fi.uu.nl> who suggested an improved data
structure format as well as binary search, to improve grepcidr performance.


COMPILING & INSTALLING
----------------------
Edit Makefile to customize the build. Then,
make
make install


COMMAND USAGE
-------------
Usage:
        grepcidr [-V] [-c] [-v] PATTERN [FILE]
        grepcidr [-V] [-c] [-v] [-e PATTERN | -f FILE] [FILE]

-V	Show software version
-c	Display count of the matching lines, instead of showing the lines
-v	Invert the sense of matching, to select non-matching IP addresses
-e	Specify pattern(s) on command-line
-f	Obtain CIDR and range pattern(s) from file

PATTERN specified on the command line may contain multiple patterns
separated by whitespace or commas. For long lists of network patterns,
specify a -f FILE to load where each line contains one pattern. Comment
lines starting with # are ignored, as are any lines that don't parse.

Each pattern, whether on the command line or inside a file, may be:
CIDR format	a.b.c.d/xx
IP range	a.b.c.d-e.f.g.h
Single IP	a.b.c.d


EXAMPLES
--------

grepcidr -f ournetworks blocklist > abuse.log
	Find our customers that show up in blocklists

grepcidr 127.0.0.0/8 iplog
	Searches for any localnet IP addresses inside the iplog file

grepcidr "192.168.0.1-192.168.10.13" iplog
	Searches for IPs matching indicated range in the iplog file

script | grepcidr -vf whitelist > blacklist
	Create a blacklist, with whitelisted networks removed (inverse)

grepcidr -f list1 list2
	Cross-reference two lists, outputs IPs common to both lists