Some systems does not receive the SIGCHLD (maybe when running under
dash?).
Unittest failed if /bin/sh was dash.

* 100% options complete with xargs. All options for xargs can now
  be used in GNU Parallel - even the more exotic.

* --basefile for transfering basedata. When running jobs on remote
  computers --basefile will transfer files before the first jobs is
  run. It can be used to transfer data that remains the same for each
  job such as scripts or lookup tables.

* --progress shows progress. To see how many jobs is running on each
  server use --progress. It can be turned on even after GNU Parallel
  is started.

* --halt-on-error stops if an error occurs. GNU Parallel will default
  to run all jobs - even if some of them fail. With --halt-on-error
  GNU Parallel can ignore errors, wait for the currently running jobs
  to finish, or stop immediately when an error occurs.

* New video showing the new options.



=head1 YouTube video

GNU Parallel is a tool with lots of uses in shell. Every time you use
xargs or a for-loop GNU Parallel can probably do that faster, safer
and more readable.

If you have access to more computers through ssh, GNU Parallel makes
it easy to distribute jobs to these.

terminal2: ssh parallel@vh2.pi.dk
ssh parallel@vh2.pi.dk
 and  

PS1="\[\e[7m\]GNU Parallel:\[\033[01;34m\]\w\[\033[00m\e[27m\]$ "
gunzip logs/*gz
rm -f logs/*bz2*
rm -rf zip/*[^p]
rm -rf dirs/*
rm -rf parallel-*bz2

xvidcap
ffmpeg -i 20100615_002.mp4 -ab 320k -ar 44100 speak.mp3
# Merge video using youtube
#ffmpeg -i speak.mp3 -i xvidcap.mpeg -target mpeg -hq -minrate 8000000 \
#-title "GNU Parallel" -author "Ole Tange" -copyright "(CC-By-SA) 2010" -comment "Intro video of GNU Parallel 20100615" videoaudio.mpg

# GNU PARALLEL - BASIC USAGE
# A GNU tool for parallelizing shell commands

# GET GNU PARALLEL
wget ftp://ftp.gnu.org/gnu/parallel/parallel-20100615.tar.bz2
tar xjf parallel-20100615.tar.bz2
cd parallel-20100615
./configure && make   ##
su
make install
exit
cd

# YOUR FIRST PARALLEL JOBS
cd logs
du
/usr/bin/time gzip -1 *
## 24 sek - 22 sek
/usr/bin/time gunzip *
## 24 sek - 18
ls | time parallel gzip -1
## 17 sek - 10
ls | time parallel gunzip
## 25 sek - 19

# RECOMPRESS gz TO bz2
ls | time parallel gzip -1
ls *.gz | time parallel -j+0 --progress 'zcat {} | bzip2 -1 > {.}.bz2'
## Explain command line
## vis top local
## Man that is boring
## 2m41s - 2m

# RECOMPRESS gz TO bz2 USING local(:) AND REMOTE server1-3
ls *.gz |time parallel -j+0 --progress -Sserver1,server2,server3,: \
--transfer --return {.}.bz2 --cleanup 'zcat {} | bzip2 -1 > {.}.bz2'
## Explain command line
## Explain server config
## vis top local
## vis top remote1-3
## 49 sek

# RECOMPRESS gz TO bz2 USING A SCRIPT ON local AND REMOTE server1-3
# (imagine the script is way more complex)
cp ../recompress /tmp
cat /tmp/recompress
ls *.gz |time parallel -j+0 --progress -Sserver1,server2,server3,: \
--trc {.}.bz2 --basefile /tmp/recompress '/tmp/recompress {} {.}.bz2'


# MAKING SMALL SCRIPTS
cd ../zip
ls -l
ls *.zip | parallel 'mkdir {.} && cd {.} && unzip ../{}' ###
ls -l

# GROUP OUTPUT
traceroute debian.org
traceroute debian.org & traceroute freenetproject.org  ###
(echo debian.org; echo freenetproject.org) | parallel traceroute ###

# KEEP ORDER
(echo debian.org; echo freenetproject.org) | parallel -k traceroute ###

# RUN MANY JOBS. USE OUTPUT
# Find the number of hosts responding to ping
ping -c 1 178.63.11.1
ping -c 1 178.63.11.1 | grep '64 bytes'
seq 1 255 | parallel -j255 ping -c 1 178.63.11.{} 2>&1 \
| grep '64 bytes' | wc -l
seq 1 255 | parallel -j0 ping -c 1 178.63.11.{} 2>&1 \
| grep '64 bytes' | wc -l

# MULTIPLE ARGUMENTS
# make dir: test-(1-20000).dir
cd ../dirs
rm -rf *; sync
seq 1 10 | parallel echo mkdir test-{}.dir
seq 1 5000 | time parallel mkdir test-{}.dir
## 15 sek

rm -rf *; sync
seq 1 10 | parallel -X echo mkdir test-{}.dir
seq 1 5000 | time parallel -X mkdir test-{}.dir

# CALLING GNU PARALLEL FROM GNU PARALLEL
# make dir: top-(1-100)/sub-(1-100)
rm -rf *; sync
seq 1 100 | time parallel -I @@ \
'mkdir top-@@; seq 1 100 | parallel -X mkdir top-@@/sub-{}'
find | wc -l

cd
# Thank you for watching
#
# If you like GNU Parallel:
# * Post this video on your blog/Twitter/Facebook/Linkedin
# * Join the mailing list http://lists.gnu.org/mailman/listinfo/parallel
# * Request or write a review for your favourite magazine
# * Request or build a package for your favourite distribution
# * Invite me for your next conference (Contact http://ole.tange.dk)
#
# If GNU Parallel saves you money:
# * Donate to FSF https://my.fsf.org/donate/
#
# Find GNU Parallel at http://www.gnu.org/software/parallel/


# GIVE ME THE FIRST RESULT
(echo foss.org.my; echo debian.org; echo freenetproject.org) | parallel -H2 traceroute {}";false"

find . -type f | parallel -k -j150% -n 1000 -m grep -H -n STRING {}

(echo foss.org.my; echo debian.org; echo freenetproject.org) | parallel traceroute


=head1 IDEAS

Kan vi lave flere ssh'er, hvis vi venter lidt?
En ssh med 20% loss og 900 ms delay, så kan login nås på 15 sek.

Test if -0 works on filenames ending in '\n'

If there are nomore jobs (STDIN is eof) then make sure to
distribute the arguments evenly if running -X.

=head1 options

One char options not used: F G J K P Q Y

Skilletegn i sshlogin:
#=item B<--sshlogin> I<[ncpu/]sshlogin[,[ncpu/]sshlogin[,...]]> (beta testing)
# Skilletegn:
# No: "#!&()?\<>|;*'~ shellspecial
# No: @.- part of user@i.p.n.r i.p.n.r host-name
# No: , separates different sshlogins
# No: space Will make it hard to do: 8/server1,server2
# Maybe: / 8//usr/bin/myssh,//usr/bin/ssh
# %/=:_^



=head2 mutex

mutex -b -n -l lockid -m max_locks [command]
mutex -u lockid

-b run command in background 
-l lockfile will lock using the lockid
-n nonblocking
-m maximal number of locks (default 1)
-u unlock

If command given works like: mutex -l lockfile -n number_of_locks ; command; mutex -u lockfile
If -b given works like: mutex -l lockfile -n number_of_locks ; (command; mutex -u lockfile)&

Kan vi finde på lockid som giver mening?

Parallelize so this can be done:
mdm.screen find dir -execdir mdm-run cmd {} \;
Maybe:
find dir -execdir par$ --communication-file /tmp/comfile cmd {} \;

find dir -execdir mutex -j4 -b cmd {} \;

=head2 Comfile

This will put a lock on /tmp/comfile. The number of locks is the number of running commands.
If the number is smaller than -j then it will start a process in the background ( cmd & ),
otherwise wait.

par$ --wait /tmp/comfile will wait until no more locks on the file



=head1 Unlikely

Accept signal INT instead of TERM to complete current running jobs but
do not start new jobs. Print out the number of jobs waiting to
complete on STDERR. Accept sig INT again to kill now. This seems to be
hard, as all foreground processes get the INT from the shell.