This manual documents gnu Proxyknife(version 1.7, 24 September 2007), the customizable proxyhunter.
Copyright © 2005, 2006, 2007 Jia WangPermission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
gnu Proxyknife is a customizable multithread proxy hunter. Tt can help users behind strict firewall find suitable free proxies.
gnu Proxyknife reads proxylist1 from the file, stdin or the web, then validates the free proxies and prints the good ones. Time intervals and the others which are userful to estimate the speed or capability of every proxy are also printed. The whole processing can be customized by the user, which is different from the other hunters.
In url mode, Proxyknife can read a large number of proxies on machines with little memory. Tt works on GNU/Linux, SunOS, OSF1 or more.
As a proxy hunter, Proxyknife can validate all kinds of proxies with different methods: HTTP proxy with GET or CONNECT method, SOCKS5 proxy with CONNECT command, SOCKS4 proxy with CONNECT command. As a customizable extension, it can check proxies for special purpose, such as finding tunnels for MSN chatting.
Proxyknife can check proxies via a tunnel. The tunnel can be SOCKS4 proxy, SOCKS5 proxy or HTTP proxy, with or without authentication for the latter two. The route from the local machine that proxyknife runs on to checksite is:
proxyknife -------- (myproxy) ------ testproxy ----- checksite
Here myproxy is the tunnel, testproxy is the free proxy being checked and checksite is the site used to validate free proxies.
Proxyknife have many features. Please see the file FEATURELIST included in this package for details.
./proxyknife [OPTION]...
If proxyknife is invoked without arguments, it will read proxylist from the file named proxylist in the current directory. The result will be written to a file named proxyout in the current directory, together with the verbose output on screen.
To change the default parameters, switch the mode or invoke it for special purpose, you can do it in two ways: permanatly, add the setting to the start file (see Startup File), or specifying it on the command line. You can also specify the startup file (see Startup File) on the command line.
Some constants in the souce code:
#define HTTP_GET 0
#define HTTP_CONNECT 1
#define SOCKS5_CONNECT 2
#define SOCKS4_CONNECT 5
#define HTTP_CONNECT_AUTH 11
#define SOCKS5_CONNECT_AUTH 12
#define DIRECT 21
#define IN_FILE 0
#define IN_HTTP 1
#define LOGSTDERR "."
Please use the value but not the former string on command line or in startup file (see Startup File).
Anyone of the following options have a `keyword' form which can be specified in startup file (see Startup File). In this section, every single option is followed by a `keyword'.
If you have duplicate options on command line or settings in startup file (see Startup File), only the first one will be used. Anyway, do not let this happen if possible.
Argument after this option is not required and should be completely omitted on command line. If this option exists, the value will be set to 1 automatically.
While in startup file, use `debug=1' to turn on debug output. `debug=0' to disable it. The value is 0 by default.
By default, proxyknife will read file proxylist in current directory in file mode and fetch proxylist from http://proxylist.kmip.net/list.html in url mode.
Default: 0
proxyknife -l .
or add this to startup file:
logfilename=.
If you want to see it later:
proxyknife -l ./proxyknife.log
or add this to startup file:
logfilename=./proxyknife.log
Default: `proxyknife.log'
Read the proxylist from local file /tmp/mylist.txt:
proxyknife -i /tmp/mylist.txt
Do the same with 100 threads:
proxyknife -i /tmp/mylist.txt -t 100
Find http proxy supporting CONNECT:
proxyknife -i /tmp/mylist.txt -H1
Find http proxy supporting ftp with GET method:
proxyknife -i /tmp/myhttplist.txt -c 'ftp://somesite/' -k 'pub'
Print the result to a file named myoutput.txt
proxyknife -i /tmp/mylist.txt -o myoutput.txt
Check the newlist again with CONNECT checking for the HTTP proxies:
proxyknife -i ./myoutput.txt -H1
Identify as firefox 2.0:
proxyknife -g 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1) Gecko/20061010 Firefox/2.0' \
-i /tmp/mylist.txt
Print more to screen:
proxyknife -i /tmp/mylist.txt -o . -d
Tips:
As a test, proxyknife can download the proxylist from the web automatically and extract the proxylist embed in the web. After the download is completed, the validating begin. Now only two sites are supported:
Using http://proxylist.kmip.net/list.html.
proxyknife -I1
Using http://youth.bupt.edu.cn/proxy/.
proxyknife -I1 -i 'youth.bupt.edu.cn/proxy/'
proxyknife -I1 -i 'youth.bupt.edu.cn/proxy/' -m11 \
-h myproxy.com -p 8080 -u userabc -s 'pass12345'
Is it too long? Then write these to startup file (see Startup File):
mytype=11
myhost=myproxy.com
myport=8080
myuser=userabc
mypass=pass12345
proxyknifeintype=1
proxyknifein=youth.bupt.edu.cn/proxy/
After that, invoke proxyknife without arguments will do the same thing:
proxyknife
proxyknife -I1 -i 'youth.bupt.edu.cn/proxy/' -m1 -hmyproxy.com -p 8080
proxyknife -I1 -m5 -hmyproxy.com -p1080
proxyknife -m2 -hmyproxy.com -p1080
proxyknife -m12 -hmyproxy.com -p1080 -u'userabc' -p'pass123'
Proxyknife can send customized request, that is to say, you can even check some unknown services with it.
I write a sample file named msn.req, which is included in this package. With this file, you can check whether a proxy can work as a MSN tunnel, that is to say, whether you can do MSN chatting via that proxy.
proxyknife -I1 -H1 -c messenger.hotmail.com:1863 -C msn.req -k `cat msn.req`
Every Startup Option (see Startup Options) can be added to startup file using the `keyword' listed after it on that section (see Startup Options).
For instance, you can replace `-t 20' with the setting:
threads=20
Then you can remove `-t 20' from the command line.
The syntax of startup file:
user_agent=User-Agent: MSIE 6.0
If you invoke proxyknife with a startup option (see Startup Options), the setting relation to it in startup file will be overridden.
By default, proxyknife will search the startup file in this order until one of them is found:
proxyknife -f /tmp/mystartup.txt
Want to validate: Free http proxy supporting CONNECT method, free socks5 or socks4 proxy supporting CONNECT command.
Your startup file should look like this:
#Connect to proxies to be checked directly.
#For http proxies, try to check with connect method.
mytype=21
httptestmethod=1
proxyknifeintype=1
Want to validate: Free http, socks5 or socks4 proxy that can be used as MSN tunnel.
The content of your startup file will be:
#Check http,socks5,socks4 proxies with customized request: msn.req.
#Check is done via a tcp tunnel(http proxy).
mytype=11
myhost=www.myhttptunnel.com
myport=8080
myuser=abc
mypass=123
httptestmethod=1
checksite=messenger.hotmail.com:1863
checkreqin=msn.req
key=VER 0 MSNP8 CVR0
proxyknifeintype=1
proxyknifein=youth.bupt.edu.cn/proxy/
Want to validate: Free http proxy with common GET method, socks5 or socks4 proxy with CONNECT command.
You can write these to your startup file:
#Check http proxies with GET method.
#Checking is done via a tcp tunnel(here http proxy).
mytype=1
myhost=www.somehttpproxy.com
myport=8080
Want to validate: Common free http proxy, free socks5 or socks4 proxy which support connect command.
Your setting should be similiar with this:
#Find http proxies with GET method, socks4/socks5 proxies with connect cmd
#All is done via a tcp tunnel(socks5 proxy) with username/password auth.
mytype=12
myhost=socks.you.com
myport=1080
myuser=phc
mypass=678
proxyknifeintype=1
proxyknifein=youth.bupt.edu.cn/proxy/
#The number of threads
#threads=50
#Turn on debug1 to debug, 0 to disable it.
#debug=0
#The meaning of some constants(These aren't keyword, only reference):
#define HTTP_GET 0
#define HTTP_CONNECT 1
#define SOCKS5_CONNECT 2
#define SOCKS4_CONNECT 5
#Send CONNECT request to http proxy with authentication
#define HTTP_CONNECT_AUTH 11
#Send CONNECT request to socks5 proxy with authentication
#define SOCKS5_CONNECT_AUTH 12
#Do not use myproxy
#define DIRECT 21
#The value of mytype must be 1,2,5,11,12 or 21 now, as defined above
#mytype=21
#myhost=www.somehttpproxy.com
#myport=8080
#Authenticate
#myuser=username
#mypass=password
#The site used to validate free proxies
#checksite=http://www.google.com:80/webhp?hl=en
#For msn
#checksite=messenger.hotmail.com:1863
#key=2006 Google
#For msn
#key=VER 0 MSNP8 CVR0
#Some references
#define HTTP_GET 0
#define HTTP_CONNECT 1
#define SOCKS5_CONNECT 2
#define SOCKS4_CONNECT 5
#The value of httptestmethod can only be 1 or 0 now.
#httptestmethod=0
#Must be 2 now, do not change it
#socks5testmethod=2
#Must be 5 now, do not change it
#socks4testmethod=5
#Size of buffer used to receive reply after sending CONNECT req to myproxy
#myconreplysize=256
#Size of buffer used to receive reply after sending CONNECT req to testproxy.
#testconreplysize=256
#The size of buffer used to store data from the target. Key was searched in it.
#testtagreplysize=65535
#Identify as
#user_agent=User-Agent: MSIE 6.0
#Specify the receiving timeout, in seconds, 0 to disable
#rcvtimeo=10
#Specify the sending timeout, in seconds, 0 to disable
#sndtimeo=5
##define LOGSTDERR "."
#Redirect stderr to log file. Use "." to leave stderr as it is.
#logfilename=.
#logfilename=proxyknife.log
#Reference
#define IN_FILE 0
#define IN_HTTP 1
#The type of proxyknifein or the mode of Proxyknife. 0:file,1:http.
#proxyknifeintype=0
#The proxylist file or url with full path
#File mode:
#proxyknifein=proxylist
#Read from stdin:
#proxyknifein=-
#In url mode, only these two sites are tested. Select one of them.
#proxyknifein=proxylist.kmip.net/list.html
#proxyknifein=youth.bupt.edu.cn/proxy/
#Print the result to this file with full path
#proxyknifeout=proxyout
#Customize the request
#checkreqin=msn.req
Here is a sample of the result (The result is included in proxyout by default):
222.216.109.55:3128@HTTPC 0.032189 0.126676 0.161449 0.034833 HTTP:GET
64.34.113.100:80@HTTPC 0.372466 0.367725 1.555638 0.375829 HTTP:GET
59.41.253.35:80@HTTPC 0.025951 4.463531 0.687924 1.077910 HTTP:GET
The format is described in section Output (see Output).
Now type `bash', then you can sort the result like the following:
sort -nk 4 proxyout
The output:
222.216.109.55:3128@HTTPC 0.032189 0.126676 0.161449 0.034833 HTTP:GET
59.41.253.35:80@HTTPC 0.025951 4.463531 0.687924 1.077910 HTTP:GET
64.34.113.100:80@HTTPC 0.372466 0.367725 1.555638 0.375829 HTTP:GET
sort -nk 5 proxyout
The output:
222.216.109.55:3128@HTTPC 0.032189 0.126676 0.161449 0.034833 HTTP:GET
64.34.113.100:80@HTTPC 0.372466 0.367725 1.555638 0.375829 HTTP:GET
59.41.253.35:80@HTTPC 0.025951 4.463531 0.687924 1.077910 HTTP:GET
cat proxyout |while read proxy a b c d req;\
do echo $proxy $a $b $c $d `echo $a+$b+$c+$d|bc` $req;done |\
sort -nk 6
The output:
222.216.109.55:3128@HTTPC 0.032189 0.126676 0.161449 0.034833 .355147 HTTP:GET
64.34.113.100:80@HTTPC 0.372466 0.367725 1.555638 0.375829 2.671658 HTTP:GET
59.41.253.35:80@HTTPC 0.025951 4.463531 0.687924 1.077910 6.255316 HTTP:GET
Replace user_agent with another HTTP header, such as Cookie:
proxyknife -g 'Cookie: var=value; var2=someting'
Create proxylist on-the-fly. In this example proxyknife scans free proxies with ip ranging from 127.0.0.1 to 127.0.0.254, the checked port is 3128:
bash
$ for ((i=1;i<255;i++));do echo 127.0.0.$i:3128@HTTP;done|proxyknife -i -
With the customized request, you can do more things.
SSH scan:
echo "127.0.0.1:22"|proxyknife -i- -I0 -H0 -C ssh.req -k mismatch
Do the same scan via the free proxy 127.0.0.5:
echo "127.0.0.5:3128"|proxyknife -i- -I0 -H1 -C ssh.req -c 127.0.0.1:22 -k mismatch
The content of proxylist should be like this:
ip:port@proto.*
or
ip:port
I remove support on domain, so ip must be IPV4 address. The port must be integer range from 1 to 65535. The proto can only be HTTP,http,socks5,SOCKS5,socks4 or SOCKS4. All of the chars afterproto will be ignored.
If there is no @ or other chars after the port in the line,proto is regarded as http by default.
Example:
61.132.89.130:80@HTTP
202.123.52.156:8080
Every line of the result is in the form of `host:port@PROTOCOLMETHOD estab pcon end req'.A sample of the output:
222.216.109.55:3128@HTTPC 0.032189 0.126676 0.161449 0.034833 HTTP:GET
64.34.113.100:80@HTTPC 0.372466 0.367725 1.555638 0.375829 HTTP:GET
59.41.253.35:80@HTTPC 0.025951 4.463531 0.687924 1.077910 HTTP:GET
By default, proxyknife use the default testmethod, the req field will be filed with `HTTP:GET' now. If you use your own testmethod with `-C msn.req' (see Startup Options) (see Customize Request) on command line or `checkreqin=msn.req' in startup file (see Startup File), this field will be filled with the argument or value, the filename of the request file, which is 'msn.req' in this case.
The current version of proxyknife output timeouts of every steps of validation:
| Method | Output (time increase ->)
|
|---|---|
| HTTP_GET | host:port@HTTPG estab 0 pget end req
|
| HTTP_CONNECT | host:port@HTTPC estab pcon get end req
|
| SOCKS5_CONNECT | host:port@SOCKS5C estab pcon get end req
|
| SOCKS4_CONNECT | host:port@SOCKS4C estab pcon get end req
|
The chart of validating:
Proxyknife -- (myproxy) --- testproxy -- target(checksite)
ta ---------------->
estab = tb - ta
tb <----------------
tc ------------------------------>
pcon = td - tc HTTP_CONNECT,SOCKS5_CONNECT or SOCKS4_CONNECT.
td <------------------------------
te ------------------------------>
(p)get = tf - te get:HTTP_CONNECT,SOCKS5_CONNECT,SOCKS4_CONNECT,
pget:HTTP_GET
tf <------------------------------
tg ------------------------------>
end = th - tg
th <------------------------------
|
The meaning of symbols in the chart:
| symbol | meaning
|
|---|---|
| – | start to send, the left string is time.(such as ta)
|
| <- | The data entered,the left string is the time when data come in.
|
| ta tb tc td te tf tg | coordinate time in seconds during a single validating
|
| delay | define
|
|---|---|
| estab | Delay from the time(ta) proxyknife send CONNECT request for testproxy to myproxy(or begin to connect to testproxy directly) to the time(tb) it receives `Connection Established'(or the connection to testproxy is completed).
|
| pcon | Delay from the time(tc) proxyknife send CONNECT request for checksite to testproxy to the time(td) it receives `Connection Established'. With HTTP_GET method, it is impossilbe to get pcon, which is included in pget delay.
|
| get | Delay from the time(te) proxyknife send HTTP GET request for checksite to testproxy to the time(tf) it receives the first byte data returned. Exclusive for HTTP_GET method.
|
| pget | Delay from the time(te) proxyknife send GET request for checksite to testproxy to the time(tf) it receives the first byte data returned.
|
| end | Delay from the time(tg or tf) proxyknife receive the first byte data to the time(th) it receives data including key.
|
If we define `TP' as `testproxy', `TG' as `checksite', then we got the `approximate mathematics' of the delays:
estab resp of TP
pcon resp of TP + relay of TP + resp of TG
get resp of TP + relay of TP + resp of TG + servicestart of TG
pget resp of TP + 3/2*relay of TP + 2*resp of TG + servicestart of TG
end 0.5*resp of TP + 0.5*relay of TP + 0.5*resp of TG + serviceend of TG
total 4.5*resp of TP + 4*relay of TP + 4.5*resp of TG + serviceall of TG
2*end-get 2*servicedata + service(2*stop-start)
relay: time(data_out) - time(data_in).
resp: response.
serviceend = time intervals(send data) + time intervals(stop this task).
A guide to use the result:
If you still feel puzzled, these tips are for you:
This is the common choice if you need quick responses to all of the sites in average.
It is a good choice if you care the first response from the checksite (see Startup Options) only.
Bandwith but not delay is important to bulk download.
Some of other proxy hunters prefer the total delay. From the approximate mathematics and the chart, I can't get the same conslusion. I think the total delay is not as useful as estab,pcon,pget,get or even end. If you have some different ideas, please send email to bug-proxyknife@gnu.org.
Tips: The less delay, the more speed. You should select the testproxies with the shortest delay, such as estab,pcon,get,pget or end.
Please send mail to bug-proxyknife-request@gnu.org with no body and a Subject: header line of just "subscribe" to subscribe yourself to this list. Alternatively, you can subscribe yourself to the list at http://lists.gnu.org/mailman/listinfo/bug-proxyknife.
Copyright © 2005, 2006, 2007 Jia WangPermission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
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To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
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Permission is granted to copy, distribute and/or modify this document
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Copyright © 2007 Free Software Foundation, Inc. http://fsf.org/
Everyone is permitted to copy and distribute verbatim copies of this
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The GNU General Public License is a free, copyleft license for software and other kinds of works.
The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program—to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.
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When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.
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You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.
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An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
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A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.
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If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.
A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.
If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.
Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.
The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.
Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.
one line to give the program's name and a brief idea of what it does.
Copyright (C) year name of author
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:
program Copyright (C) year name of author
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.
You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see http://www.gnu.org/licenses/.
The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read http://www.gnu.org/philosophy/why-not-lgpl.html.