Provided by: grepcidr_2.0-2_amd64 bug


       grepcidr — Filter IPv4 and IPv6 addresses matching CIDR patterns


       grepcidr [OPTIONS]  PATTERN [FILE...]

       grepcidr [OPTIONS]  [-e PATTERN | -f PATFILE]  [FILE...]


       grepcidr can be used to filter a list of IP addresses against one or more Classless Inter-
       Domain Routing (CIDR) specifications.  As with grep, there are options to invert  matching
       and  load  patterns  from  a  file.   grepcidr  is capable of efficiently processing large
       numbers of IPs and networks.


       -V        Show software version

       -c        Display count of the matching lines, instead of showing the lines

       -i        Inverse match, include lines without an IP, implies -v

       -s        Enforce strict alignment of CIDR mask; host portion must be all zero

       -v        Invert the sense of matching, output lines with IPs that don't match

       -x        Strict matching, only look at start of line

       -e        Specify individual IP or CIDR pattern(s) on command-line

       -f        Load individual IP or CIDR 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, use -f to load a file where each
       line contains one pattern (can be IPv4 or IPv6).  Blank lines and comments starting with #
       are ignored.

       Each IPv4 pattern, whether on command line or loaded from a file, may be:

       a.b.c.d/xy        (CIDR format)
       a.b.c.d-e.f.g.h   (IP range)
       a.b.c.d           (Single IP)

       And similarly for IPv6:

       a:b:c::/xyz       (CIDR format)
       a:b:c::           (Single IP)

       Dotted-decimal IPv4 format, or any legal IPv6 format is supported (see: man inet_pton).

       IP  addresses  that appear anywhere on the input line will be compared and matched against
       the patterns.  To be recognized, an IP (field) must end with terminating  text.   An  IPv4
       field  terminates  upon anything other than alphanumeric or dot.  An IPv6 field terminates
       upon anything other than alphanumeric, dot, or  colon.   This  is  to  prevent  accidental
       matching of ambiguous text such as host names containing reverse DNS.

       Use the -x option to do a strict parse without searching the whole line, and grepcidr will
       only look for the single IP at the start of the line.


       grepcidr -f ournetworks blacklist > abuse.log

       Find customers (CIDR ranges in file) that appear in blacklist

       grepcidr 2001:db8::/32 log.1 log.2

       Search for this IPv6 network inside two files

       grepcidr iplog

       Searches for any localnet IP addresses inside the iplog file

       grepcidr "" 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


       As with grep: the exit status is 0 if matching IPs are found, and 1 if not found.   If  an
       error occurred the exit status is 2.


       This software and manual page was written by Jem Berkes <> based on the first
       man page and DocBook format contributed by Ryan Finnie.  Permission is  granted  to  copy,
       distribute  and/or modify this document under the terms of the GNU General Public License,
       Version 2 or any later version published by the Free Software Foundation.



       Sponsored in part by the Spamhaus Project,

       Thanks to John Levine <> for sharing  his  alternative  implementation.   I
       used  a  couple  ideas  from  his  code,  such as portable 128-bit numbers and support for
       multiple input files.  However,  John's  version  is  quite  different  and  represents  a
       significant fork in the project.

       Thanks  to Ryan Finnie <> for his work on the Debian package.  I've adopted
       several of his changes including the Makefile, and the DocBook format  which  now  is  the
       source of the man page.  Thanks to Ryan for writing the first manual in DocBook format.

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