|
Home | Switchboard | Unix Administration | Red Hat | TCP/IP Networks | Neoliberalism | Toxic Managers |
(slightly skeptical) Educational society promoting "Back to basics" movement against IT overcomplexity and bastardization of classic Unix |
qsub
[-A account_string]
[-c checkpoint_options]
s Checkpointing is to be performed only when the server
executing the job is shutdown .
the job.
Checkpointing is to be performed at an interval of minutes,
which is the integer number
[-C directive_prefix] [-d path] [-D path] [-e path] [-f] [-h]
[-j join
]
[-l resource_list ]
[-M user_list]
[-o path]
[-P user[:group]]
[-r c]
[-t array_request]
[- v
variable_list]
[-W additional_attributes]
[-z]
|
For detailed information, see this page.
qsub is the command used for job submission to the cluster. It takes several command line arguments and can also use special directives found in the submission scripts or command file. Several of the most widely used arguments are described in detail below.
Useful Information
For more information on qsub doMore information on qsub
?$ man
qsub |
All of our clusters have a batch server referred to as the cluster management server running on the headnode. This batch server monitors the status of the cluster and controls/monitors the various queues and job lists. Tied into the batch server, a scheduler makes decisions about how a job should be run and its placement in the queue. qsub interfaces into the the batch server and lets it know that there is another job that has requested resources on the cluster. Once a job has been received by the batch server, the scheduler decides the placement and notifies the batch server which in turn notifies qsub (Torque/PBS) whether the job can be run or not. The current status (whether the job was successfully scheduled or not) is then returned to the user. You may use a command file or STDIN as input for qsub.
The qsub command will pass certain environment variables in the Variable_List attribute of the job. These variables will be available to the job. The value for the following variables will be taken from the environment of the qsub command:
These values will be assigned to a new name which is the current name prefixed with the string "PBS_O_". For example, the job will have access to an environment variable named PBS_O_HOME which have the value of the variable HOME in the qsub command environment.
In addition to these standard environment variables, there are additional environment variables available to the job.
As stated before there are several arguments that you can use to get your jobs to behave a specific way. This is not an exhaustive list, but some of the most widely used and many that you will will probably need to accomplish specific tasks.
To set the date/time which a job becomes eligible to run, use the -a argument. The date/time format is [[[[CC]YY]MM]DD]hhmm[.SS]. If -a is not specified qsub assumes that the job should be run immediately.
To test -a get the current date from the command line and add a couple of minutes to it. It was 10:45 when I checked. Add hhmm to -a and submit a command from STDIN.
Example: Set the date/time which a job becomes eligible to run$ echo
"sleep 30" | qsub -a 1047 |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -a 1047 |
To define the working directory path to be used for the job -d option can be used. If it is not specified, the default working directory is the home directory.
$ pwd
$ cat
dflag.pbs
echo "Working directory is $PWD"
5596682.hpc0. local
Working directory is /home/manchu
$ qsub -d /home/manchu/random_pbs/ /home/manchu/random_pbs/dflag.pbs
$ cat
random_ps/dflag.pbs.o5596703
$ qsub /home/manchu/random_pbs/dflag.pbs
$ cat
dflag.pbs.o5596704
|
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -d /home/manchu/random_pbs |
As a default all jobs will print all stdout (standard output) messages to a file with the name in the format <job_name>.o<job_id> and all stderr (standard error) messages will be sent to a file named <job_name>.e<job_id>. These files will be copied to your working directory as soon as the job starts. To rename the file or specify a different location for the standard output and error files, use the -o for standard output and -e for the standard error file. You can also combine the output using -j.
$ cat
sleep .pbs
echo $i
done |
$ qsub -o sleep .log
sleep .pbs |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -o sleep.log |
$ qsub -e sleep .log
sleep .pbs |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -e sleep.log |
$ qsub -o sleep .log
-j oe sleep .pbs |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -o sleep.log
|
Warning
The order of two letters next to flag -j is important. It should always start with the letter that's been already defined before, in this case 'o'.Place the joined output in another location other than the working directory:
?$ qsub -o $HOME/tutorials/logs/sleep.log -j oe
sleep .pbs |
The mailing options are set using the -m and -M arguments. The -m argument sets the conditions under which the batch server will send a mail message about the job and -M will define the users that emails will be sent to (multiple users can be specified in a list seperated by commas). The conditions for the -m argument include:
$ qsub -m abe -M [email protected]
sleep .pbs |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -m abe
|
You can select a queue based on walltime needed for your job. Use the 'qstat -q' command to see the maximum job times for each queue.
$ qsub -q bigmem
sleep .pbs |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -q bigmem |
Often you will have jobs that will be dependent on another for output in order to run. To add a dependency, we will need to use the -W (additional attributes) with the depend option. We will be using the afterok rule, but there are several other rules that may be useful. (man qsub)
To illustrate the ability to hold execution of a specific job until another has completed, we will write two submission scripts. The first will create a list of random numbers. The second will sort those numbers. Since the second script will depend on the list that is created we will need to hold execution until the first has finished.
random.pbs$ cat
random.pbs
cd $HOME
for i
in {1..100};
do
done |
$ cat
sort .pbs
cd $HOME
sleep 30 |
Once the file are created, lets see what happens when they are submitted at the same time:
Submit at the same time$ qsub random.pbs ; qsub
sort .pbs
5594671.hpc0. local
random.pbs sorted.list
sort .pbs
sort .pbs.e5594671
sort .pbs.o5594671
sort :
open failed: rand.list: No such
file or directory |
Since they both ran at the same time, the sort script failed because the file rand.list had not been created yet. Now submit them with the dependencies added.
Submit them with the dependencies added$ qsub random.pbs
$ qsub -W depend=afterok:5594674.hpc0. local
sort .pbs
$ qstat -u $USER
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5594675.hpc0.loc manchu ser2
sort .pbs
1 1 -- 48:00 H -- |
We now see that the sort.pbs job is in a hold state. And once the dependent job completes the sort job runs and we see:
Job status with the dependencies added$ qstat -u $USER
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
|
Useful Information
This example show how to submit multiple jobs in a loop where each job depends on output of job submitted before it.
Let's say we need to write numbers from 0 to 999999 in order onto a file output.txt. We can do 10 separate runs to achieve this, where each run has a separate pbs script writing 100,000 numbers to output file. Let's see what happens if we submit all 10 jobs at the same time.
The script below creates required pbs scripts for all the runs.
Create PBS Scripts for all the runs$ cat
creation.sh
do
#!/bin/bash
{
}
done |
$ chmod
u+x creation.sh |
$ ./creation.sh |
$ ls
-l pbs.script.*
-rw-r--r-- 1 manchu wheel 139 Oct 27 16:32 pbs.script.1
-rw-r--r-- 1 manchu wheel 139 Oct 27 16:32 pbs.script.3
-rw-r--r-- 1 manchu wheel 139 Oct 27 16:32 pbs.script.5
-rw-r--r-- 1 manchu wheel 139 Oct 27 16:32 pbs.script.7
-rw-r--r-- 1 manchu wheel 140 Oct 27 16:32 pbs.script.9 |
$ cat
pbs.script.0
{
}
|
$ for
i in
{0..9}; do
qsub pbs.script.$i ; done
5633532.hpc0. local
5633534.hpc0. local
5633536.hpc0. local
5633538.hpc0. local
5633540.hpc0. local
|
$ tail
output.txt
699991
699993
699995
699997
699999
210510:999999
|
This clearly shows the nubmers are in no order like we wanted. This is because all the runs wrote to the same file at the same time, which is not what we wanted.
Let's submit jobs using qsub dependency feature. This can be achieved with a simple script shown below.
Simple Script to Submit Multiple Dependent Jobs$ cat
dependency.pbs
for i
in {1..9}
job_next=`qsub -W
depend=afterok:$job pbs.script.$i`
done |
$ chmod
u+x dependency.pbs |
$ ./dependency.pbs
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5633542.hpc0.loc manchu ser2
pbs.script.1 -- 1
1 -- 00:10 H --
5633544.hpc0.loc manchu ser2
pbs.script.3 -- 1
1 -- 00:10 H --
5633546.hpc0.loc manchu ser2
pbs.script.5 -- 1
1 -- 00:10 H --
5633548.hpc0.loc manchu ser2
pbs.script.7 -- 1
1 -- 00:10 H --
5633550.hpc0.loc manchu ser2
pbs.script.9 -- 1
1 -- 00:10 H --
|
$ tail
output.txt
99991
99993
99995
99997
99999
|
$ tail
output.txt
999991
999993
999995
999997
999999
100001:100000
1000000:999999
|
This shows that numbers are written in order to output.txt. Which in turn shows that jobs ran one after successful completion of another.
To open an interactive shell to a compute node, use the -I argument. This is often used in conjunction with the -X (X11 Forwarding) and the -V (pass all of the users environment)
$ qsub -I |
You can pass user defined environment variables to a job by using the -v argument.
To test this we will use a simple script that prints out an environment variable.
Passing an environment variable$ cat
variable.pbs
if [
"x" ==
"x$MYVAR" ] ;
then
else
fi |
Next use qsub without the -v and check your standard out file
qsub without -v$ qsub variable.pbs
$ cat
variable.pbs.o5596675
|
Then use the -v to set the variable
qsub with -v$ qsub - v
MYVAR= "hello"
variable.pbs
$ cat
variable.pbs.o5596676
|
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -v MYVAR="hello" |
Useful Information
Multiple user defined environment variables can be passed to a job at a time.
Passing Multiple Variables
?$ cat
variable.pbs
echo "$VAR1 $VAR2 $VAR3"
> output.txt
$ qsub - v
VAR1= "hello" ,VAR2= "Sreedhar" ,VAR3= "How
are you?" variable.pbs
$ cat
output.txt
$ |
You may declare that all of your environment variables are passed to the job by using the -V argument in qsub.
Use qsub to perform an interactive login to one of the nodes:
Passing your environment: qsub with -V$ qsub -I -V |
Handy Hint
This option can be added to pbs script with a PBS directive such asEquivalent PBS Directive
?#PBS -V |
Once the shell is opened, use the env command to see that your environment was passed to the job correctly. You should still have access to all your modules that you loaded previously.
Sometimes users will want to submit large numbers of jobs based on the same job script. Rather than using a script to repeatedly call qsub, a feature known as job arrays exists to allow the creation of multiple jobs with one qsub command. Additionally, this feature includes a new job naming convention that allows users to reference the entire set of jobs as a unit, or to reference one particular job from the set. Each job submitted will have a job id in the format <id>[<num>].hostname. In the case of a submission number of 5554444, each 5554444[x] job has an environment variable called PBS_ARRAYID, which is set to the value of the array index of the job, so 55544440.hostname would have PBS_ARRAYID set to 0. This will allow you to create job arrays where each job in the array will perform slightly different actions based on the value of this variable, such as performing the same tasks on different input files. One other difference in the environment between jobs in the same array is the value of the PBS_JOBNAME variable.
First we need to create data to be read. Note that in a real application, this could be data, configuration setting or anything that your program needs to run.
To create input data, run this simple one-liner:
Creating input data$ for
i in
{0..4}; do
echo "Input data file for an array
$i" > input.$i ; done
input.0 input.1 input.2 input.3 input.4
Input data file
for an array 0 |
$ cat
array.pbs
#PBS -N arraytest
# This part of the script handles the data. In a real world situation
you will probably
cat input.${PBS_ARRAYID} > output.${PBS_ARRAYID}
sleep 30
|
Instead of running five qsub commands, we can simply enter:
Submitting and Monitoring Array of Jobs$ qsub -t 0-4 array.pbs
|
$ qstat -u $USER
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5534017[1].hpc0. sm4082 ser2
arraytest-1 12050 1 1
-- 00:05 R --
5534017[3].hpc0. sm4082 ser2
arraytest-3 12117 1 1
-- 00:05 R --
output.0 output.1 output.2 output.3
output.4
Input data file
for an array 0
|
pbstop by default doesn't show all the jobs in the array. Instead, it shows a single job in just one line in the job information. Pressing 'A' shows all the jobs in the array. Same can be achieved by giving the command line option '-A'. This option along with '-u <NetID>' shows all of your jobs including array as well as normal jobs.
pbstop$ pbstop -A -u $USER |
Note
Typing 'A' expands/collapses array job representation.
The -t option of qsub also accepts comma delimited lists of job IDs so you are free to choose how to index the members of your job array. For example:
Comma delimited lists$ rm
output.*
5534018[].hpc0. local
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5534018[5].hpc0. sm4082 ser2
arraytest-5 12353 1 1
-- 00:05 R --
5534018[8].hpc0. sm4082 ser2
arraytest-8 12419 1 1
-- 00:05 R --
output.2 output.5 output.7 output.8
output.9
Input data file
for an array 2
|
By default, PBS doesn't allow array jobs with step size. qsub -t 0-10 <pbs.script> increments PBS_ARRAYID in 1. To submit jobs in steps of a certain size, let's say step size of 3 starting at 0 and ending at 10, one has to do
?qsub -t 0,3,6,9 <pbs.script> |
To make it easy for users we have put a wrapper which takes starting point, ending point and step size as arguments for -t flag. This avoids default necessity that PBS_ARRAYID increment be 1. The above request can be accomplished with (which happens behind the scenes with the help of wrapper)
?qsub -t 0-10:3 <pbs.script> |
Here, 0 is the starting point, 10 is the ending point and 3 is the step size. It is not necessary that starting point must be 0. It can be any number. Incidentally, in a situation in which the upper-bound is not equal to the lower-bound plus an integer-multiple of the increment, for example
?qsub -t 0-10:3 <pbs.script> |
wrapper automatically changes the upper bound as shown in the example below.
Arrays with step size[sm4082@login-0-0 ~]$ qsub -t 0-10:3 array.pbs
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
[sm4082@login-0-0 ~]$ qstat -t -u $USER
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
6390152[3].hpc0. sm4082 ser2
arraytest-3 28227 1 1
-- 00:05 R --
6390152[9].hpc0. sm4082 ser2
arraytest-9 505 1
1 -- 00:05 R --
output.0 output.3 output.6 output.9
Input data file
for an array 9
[sm4082@login-0-0 ~]$ |
Note
By default, PBS doesn't support arrays with step size. On our clusters, it's been achieved with a wrapper. This option might not be there on clusters at other organizations/schools that use PBS/Torque.
Note
If you're trying to submit jobs through ssh to login nodes from your pbs scripts with statement such asssh login-0-0
"cd ${PBS_O_WORKDIR};`which qsub` -t 0-10:3 <pbs.script>" |
arrays with step size wouldn't work unless you either add
?shopt -s expand_aliases |
to your pbs script that's in bash or add this to your .bashrc in your home directory. Adding this makes alias for qsub come into effect there by making wrapper act on command line options to qsub (For that matter this brings any alias to effect for commands executed via SSH).
If you have
?#PBS -t 0-10:3 |
in your pbs script you don't need to add this either to your pbs script or to your .bashrc in your home directory.
Suppose we have a list of 1000 input files, rather than input files explicitly indexed by suffix, in a file file_list.text one per line:
A List of Input Files/Pulling data from the ith line of a file[sm4082@login-0-2 ~]$
cat array.list
#PBS -l nodes=1:ppn=1,walltime=1:00:00
#
#
sed -n -e "${PBS_ARRAYID}p" file_list.text
#
...or use head/tail
|
In this example, the '-n' option suppresses all output except that which is explicitly printed (on the line equal to PBS_ARRAYID).
?qsub -t 1-1000 array.list |
Let’s say you have a list of 1000 numbers in a file, one number per line. For example, the numbers could be random number seeds for a simulation. For each task in an array job, you want to get the ith line from the file, where i equals PBS_ARRAYID, and use that value as the seed. This is accomplished by using the Unix head and tail commands or awk or sed just like above.
A List of Input Files/Pulling data from the ith line of a file[sm4082@login-0-2 ~]$
cat array.seed
#PBS -l nodes=1:ppn=1,walltime=1:00:00
SEED=$( cat
$SEEDFILE | head
-n $PBS_ARRAYID | tail
-n 1)
|
qsub -t 1-1000 array.seed |
You can use this trick for all sorts of things. For example, if your jobs all use the same program, but with very different command-line options, you can list all the options in the file, one set per line, and the exercise is basically the same as the above, and you only have two files to handle (or 3, if you have a perl script generate the file of command-lines).
We can delete all the jobs in array with a single command.
Deleting array of jobs$ qsub -t 2-5 array.pbs
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
$ |
Delete a single job in array, e.g. number 4,5 and 7
Deleting a single job in array$ qsub -t 0-8 array.pbs
Req 'd Req' d
Elap
----------- -- ---- ---------- ---- ---- -- ----- --- - ---
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5534021[1].hpc0. sm4082 ser2
arraytest-1 14271 1 1
-- 00:05 R --
5534021[3].hpc0. sm4082 ser2
arraytest-3 14721 1 1
-- 00:05 R --
5534021[5].hpc0. sm4082 ser2
arraytest-5 14787 1 1
-- 00:05 R --
5534021[7].hpc0. sm4082 ser2
arraytest-7 10744 1 1
-- 00:05 R --
$ qdel 5534021[5]
Req 'd Req' d
Elap
-------------------- -------- -------- ---------------- ------ -----
--- ------ ----- - -----
5534021[1].hpc0. sm4082 ser2
arraytest-1 14271 1 1
-- 00:05 R --
5534021[3].hpc0. sm4082 ser2
arraytest-3 14721 1 1
-- 00:05 R --
5534021[8].hpc0. sm4082 ser2
arraytest-8 9711 1
1 -- 00:05 R --
$ |
|
Switchboard | ||||
Latest | |||||
Past week | |||||
Past month |
Google matched content |
Society
Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers : Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism : The Iron Law of Oligarchy : Libertarian Philosophy
Quotes
War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda : SE quotes : Language Design and Programming Quotes : Random IT-related quotes : Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce : Bernard Shaw : Mark Twain Quotes
Bulletin:
Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 : Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law
History:
Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds : Larry Wall : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS : Programming Languages History : PL/1 : Simula 67 : C : History of GCC development : Scripting Languages : Perl history : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history
Classic books:
The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month : How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Hater’s Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite
Most popular humor pages:
Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor
The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D
Copyright © 1996-2021 by Softpanorama Society. www.softpanorama.org was initially created as a service to the (now defunct) UN Sustainable Development Networking Programme (SDNP) without any remuneration. This document is an industrial compilation designed and created exclusively for educational use and is distributed under the Softpanorama Content License. Original materials copyright belong to respective owners. Quotes are made for educational purposes only in compliance with the fair use doctrine.
FAIR USE NOTICE This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available to advance understanding of computer science, IT technology, economic, scientific, and social issues. We believe this constitutes a 'fair use' of any such copyrighted material as provided by section 107 of the US Copyright Law according to which such material can be distributed without profit exclusively for research and educational purposes.
This is a Spartan WHYFF (We Help You For Free) site written by people for whom English is not a native language. Grammar and spelling errors should be expected. The site contain some broken links as it develops like a living tree...
|
You can use PayPal to to buy a cup of coffee for authors of this site |
Disclaimer:
The statements, views and opinions presented on this web page are those of the author (or referenced source) and are not endorsed by, nor do they necessarily reflect, the opinions of the Softpanorama society. We do not warrant the correctness of the information provided or its fitness for any purpose. The site uses AdSense so you need to be aware of Google privacy policy. You you do not want to be tracked by Google please disable Javascript for this site. This site is perfectly usable without Javascript.
Last modified: March 20, 2020